Dariusz Miskowiec
2007-07-06T23:59:59.000Z
Based on simple physics arguments it is shown that the concept of quark-gluon plasma, a state of matter consisting of uncorrelated quarks, antiquarks, and gluons, has a fundamental problem.
Equilibration in Quark Gluon Plasma
Santosh K Das; Jan-e Alam; Payal Mohanty
2009-12-21T23:59:59.000Z
The hydrodynamic expansion rate of quark gluon plasma (QGP) is evaluated and compared with the scattering rate of quarks and gluons within the system. Partonic scattering rates evaluated within the ambit of perturbative Quantum Choromodynamics (pQCD) are found to be smaller than the expansion rate evaluated with ideal equation of state (EoS) for the QGP. This indicate that during the space-time evolution the system remains out of equilibrium. Enhancement of pQCD cross sections and a more realistic EoS keep the partons closer to the equilibrium.
HUNTING THE QUARK GLUON PLASMA.
LUDLAM, T.; ARONSON, S.
2005-04-11T23:59:59.000Z
The U.S. Department of Energy's Relativistic Heavy Ion Collider (RHIC) construction project was completed at BNL in 1999, with the first data-taking runs in the summer of 2000. Since then the early measurements at RHIC have yielded a wealth of data, from four independent detectors, each with its international collaboration of scientists: BRAHMS, PHENIX, PHOBOS, and STAR [1]. For the first time, collisions of heavy nuclei have been carried out at colliding-beam energies that have previously been accessible only for high-energy physics experiments with collisions of ''elementary'' particles such as protons and electrons. It is at these high energies that the predictions of quantum chromodynamics (QCD), the fundamental theory that describes the role of quarks and gluons in nuclear matter, come into play, and new phenomena are sought that may illuminate our view of the basic structure of matter on the sub-atomic scale, with important implications for the origins of matter on the cosmic scale. The RHIC experiments have recorded data from collisions of gold nuclei at the highest energies ever achieved in man-made particle accelerators. These collisions, of which hundreds of millions have now been examined, result in final states of unprecedented complexity, with thousands of produced particles radiating from the nuclear collision. All four of the RHIC experiments have moved quickly to analyze these data, and have begun to understand the phenomena that unfold from the moment of collision as these particles are produced. In order to provide benchmarks of simpler interactions against which to compare the gold-gold collisions, the experiments have gathered comparable samples of data from collisions of a very light nucleus (deuterium) with gold nuclei, as well as proton-proton collisions, all with identical beam energies and experimental apparatus. The early measurements have revealed compelling evidence for the existence of a new form of nuclear matter at extremely high density and temperature--a medium in which the predictions of QCD can be tested, and new phenomena explored, under conditions where the relevant degrees of freedom, over nuclear volumes, are expected to be those of quarks and gluons, rather than of hadrons. This is the realm of the quark gluon plasma, the predicted state of matter whose existence and properties are now being explored by the RHIC experiments.
Polarization energy loss in hot viscous quark-gluon plasma
Bing-Feng Jiang; Defu Hou; Jia-Rong Li
2014-05-19T23:59:59.000Z
The gluon polarization tensor for the quark-gluon plasma with shear viscosity is derived with the viscous chromohydrodynamics. The longitudinal and transverse dielectric functions are evaluated from the gluon polarization tensor, through which the polarization energy loss suffered by a fast quark traveling through the viscous quark-gluon plasma is investigated. The numerical analysis indicates that shear viscosity significantly reduces the polarization energy loss.
Quark-Gluon Plasma: a New State of Matter
Brookhaven Lab
2010-01-08T23:59:59.000Z
Physicist Peter Steinberg explains the nature of the quark gluon plasma (QGP), a new state of matter produced at Brookhaven Lab's Relativistic Heavy Ion Collider (RHIC).
Surprises from the search for quark-gluon plasma? When was quark-gluon plasma seen?
Richard M. Weiner
2006-03-13T23:59:59.000Z
The historical context of the recent results from high energy heavy ion reactions devoted to the search of quark-gluon plasma (QGP) is reviewed, with emphasis on the surprises encountered. The evidence for QGP from heavy ion reactions is compared with that available from particle reactions.
Photon production from an anisotropic quark-gluon plasma
Bjoern Schenke; Michael Strickland
2006-11-27T23:59:59.000Z
We calculate photon production from a quark-gluon plasma which is anisotropic in momentum space including the Compton scattering and quark/anti-quark annihilation processes. We show that for a quark-gluon plasma which has an oblate momentum-space anisotropy the photon production rate has an angular dependence which is peaked transverse to the beam line. We propose to use the angular dependence of high-energy medium photon production to experimentally determine the degree of momentum-space isotropy of a quark-gluon plasma produced in relativistic heavy-ion collisions.
Holography and unquenched quark-gluon plasmas
Bertoldi, G. [Department of Physics, Swansea University, Swansea, SA28PP (United Kingdom); Bigazzi, F. [Physique Theorique et Mathematique and International Solvay Institutes, Universit e Libre de Bruxelles, C.P. 231, B-1050 Bruxelles (Belgium); Cotrone, A. L. [Departament ECM, Facultat de Fisica, Universitat de Barcelona and Institut de Fisica d'Altes Energies, Diagonal 647, E-08028 Barcelona (Spain); Edelstein, J. D. [Departamento de Fisica de Particulas and IGFAE, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Centro de Estudios Cientificos (CECS), Casilla 1469, Valdivia (Chile)
2007-09-15T23:59:59.000Z
We employ the string/gauge theory correspondence to study properties of strongly coupled quark-gluon plasmas in thermal gauge theories with a large number of colors and flavors. In particular, we analyze noncritical string duals of conformal (S)QCD, as well as ten-dimensional wrapped fivebrane duals of SQCD-like theories. We study general properties of the dual plasmas, including the drag force exerted on a probe quark and the jet quenching parameter. We find that these plasma observables depend on the number of colors and flavors in the 'QCD dual'; in particular, we find that the jet quenching parameter increases linearly with N{sub f}/N{sub c} at leading order in the probe limit. In the ten-dimensional case we find a nontrivial drag coefficient but a vanishing jet quenching parameter. We comment on the relation of this result with total screening and argue that the same features are shared by all known plasmas dual to fivebranes in ten dimensions. We also construct new D5 black hole solutions with spherical horizon and show that they exhibit the same features.
Jet conversions in a quark-gluon plasma
Liu, W.; Ko, Che Ming; Zhang, B. W.
2007-01-01T23:59:59.000Z
Quark and gluon jets traversing through a quark-gluon plasma not only lose their energies but also can undergo flavor conversions. The conversion rates via the elastic q((q) over bar )g -> gq((q) over bar )and the inelastic q (q) over bar gg...
Black holes and the quark-gluon plasma
George Siopsis
2009-01-26T23:59:59.000Z
I discuss the possibility that the quark-gluon plasma at strong coupling admits a description in terms of a black hole in asymptotically anti-de Sitter space.
Dilepton Production In Non-equilibriated Quark Gluon Plasma
S. S. Singh; Agam K. Jha
2006-07-01T23:59:59.000Z
A model of cut-off momentum distribution functions in a Quark Gluon Plasma with finite baryon chemical potential is discussed. This produces a quark gluon plasma signature in Ultra Relativistic Nuclear Collisions with a specific structure of the dilepton spectrum in the transverse momentum region of $(1-4)~GeV$ and the dilepton production rate is found to be a strong decreasing function of the chemical potential.
Modeling Quark Gluon Plasma Using CHIMERA
Betty B. I. Abelev
2011-09-19T23:59:59.000Z
We attempt to model Quark Gluon Plasma (QGP) evolution from the initial Heavy Ion collision to the final hadronic gas state by combining the Glauber model initial state conditions with eccentricity fluctuations, pre-equilibrium flow, UVH2+1 viscous hydrodynamics with lattice QCD Equation of State (EoS), a modified Cooper-Frye freeze-out and the UrQMD hadronic cascade. We then evaluate the model parameters using a comprehensive analytical framework which together with the described model we call CHIMERA. Within our framework, the initial state parameters, such as the initial temperature (T$_{\\mathrm{init}}$), presence or absence of initial flow, viscosity over entropy density ($\\eta$/s) and different Equations of State (EoS), are varied and then compared simultaneously to several experimental data observables: HBT radii, particle spectra and particle flow. $\\chi^2$/nds values from comparison to the experimental data for each set of initial parameters will then used to find the optimal description of the QGP with parameters that are difficult to obtain experimentally, but are crucial to understanding of the matter produced.
Modeling Quark Gluon Plasma Using CHIMERA
Abelev, Betty B I
2011-01-01T23:59:59.000Z
We attempt to model Quark Gluon Plasma (QGP) evolution from the initial Heavy Ion collision to the final hadronic gas state by combining the Glauber model initial state conditions with eccentricity fluctuations, pre-equilibrium flow, UVH2+1 viscous hydrodynamics with lattice QCD Equation of State (EoS), a modified Cooper-Frye freeze-out and the UrQMD hadronic cascade. We then evaluate the model parameters using a comprehensive analytical framework which together with the described model we call CHIMERA. Within our framework, the initial state parameters, such as the initial temperature (T$_{\\mathrm{init}}$), presence or absence of initial flow, viscosity over entropy density ($\\eta$/s) and different Equations of State (EoS), are varied and then compared simultaneously to several experimental data observables: HBT radii, particle spectra and particle flow. $\\chi^2$/nds values from comparison to the experimental data for each set of initial parameters will then used to find the optimal description of the QGP wi...
Self-consistent quasiparticle model for quark-gluon plasma
Vishnu M. Bannur
2006-09-19T23:59:59.000Z
Here we present a self-consistent quasi-particle model for quark-gluon plasma and apply it to explain the non-ideal behaviour seen in lattice simulations. The basic idea, borrowed from electrodynamic plasma, is that the gluons acquire mass as it propagates through plasma due to collective effects and is approximately equal to the plasma frequency. The statistical mechanics and thermodynamics of such a system is studied by treating it as an ideal gas of massive gluons. Since mass or plasma frequency depends on density, which itself is a thermodynamic quantity, the whole problem need to be solved self-consistently.
Tomography of the Quark-Gluon-Plasma by Charm Quarks
Song, Taesoo; Cabrera, Daniel; Torres-Rincon, Juan M; Tolos, Laura; Cassing, Wolfgang; Bratkovskaya, Elena
2015-01-01T23:59:59.000Z
We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM) which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross section are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into $D$ mesons through coalescence and/or fragmentation depending on transverse momentum. The hadronized $D$ mesons then interact with the various hadrons in the hadronic phase with cross sect...
On the Dynamics of Unstable Quark-Gluon Plasma
Stanislaw Mrowczynski
2009-10-30T23:59:59.000Z
Since the quark-gluon plasma, which is unstable due to anisotropic momentum distribution, evolves fast in time, plasma's characteristics have to be studied as initial value problems. The chromodynamic fluctuations and the momentum broadening of a fast parton traversing the plasma are discussed here. The two quantities are shown to exponentially grow in time.
Jet conversions in a quark-gluon plasma
W. Liu; C. M. Ko; B. W. Zhang
2007-05-05T23:59:59.000Z
Quark and gluon jets traversing through a quark-gluon plasma not only lose their energies but also can undergo flavor conversions. The conversion rates via the elastic $q(\\bar q)g\\to gq(\\bar q)$ and the inelastic $q\\bar q\\leftrightarrow gg$ scatterings are evaluated in the lowest order in QCD. Including both jet energy loss and conversions in the expanding quark-gluon plasma produced in relativistic heavy ion collisions, we have found a net conversion of quark to gluon jets. This reduces the difference between the nuclear modification factors for quark and gluon jets in central heavy ion collisions and thus enhances the $p/\\pi^+$ and ${\\bar p}/\\pi^-$ ratios at high transverse momentum. However, a much larger net quark to gluon jet conversion rate than the one given by the lowest-order QCD is needed to account for the observed similar ratios in central Au+Au and p+p collisions at same energy. Implications of our results are discussed.
Baryon number fluctuation and the quark-gluon plasma
Lin, ZW; Ko, Che Ming.
2001-01-01T23:59:59.000Z
baryon number are also studied. DOI: 10.1103/PhysRevC.64.041901 PAC A new state of matter, the quark-gluon plasma, is ex- pected to be formed in heavy ion collisions at ultrarelativistic energies, such as at the Relativistic Heavy Ion Collider ~RHIC...! that has just begun its operation at the Brookhaven National Laboratory. Many observables have been proposed as possible signatures for the quark-gluon plasma phase dur- ing the collisions @1#, such as strangeness enhancement @2#, J/c suppression @3...
Viscous quark-gluon plasma model through fluid QCD approach
Djun, T. P., E-mail: tpdjun@teori.fisika.lipi.go.id [Graduate Study in Material Science, University of Indonesia, Kampus UI Salemba, Jakarta 10430, Indonesia and Group for Theoretical and Computational Physics, Research Center for Physics, Indonesian Institute of Sciences, Kompleks Puspiptek Serpong, T (Indonesia); Soegijono, B.; Mart, T. [Graduate Study in Material Science, University of Indonesia, Kampus UI Salemba, Jakarta 10430, Indonesia and Department of Physics, University of Indonesia, Kampus UI Depok, Depok 16424 (Indonesia); Handoko, L. T., E-mail: Handoko@teorifisika.lipi.go.id, E-mail: Laksana.tri.handoko@lipi.go.id [Group for Theoretical and Computational Physics, Research Center for Physics, Indonesian Institute of Sciences, Kompleks Puspiptek Serpong, Tangerang 15310, Indonesia and Research Center for Informatics, Indonesia Institute of Sciences, Kompleks LIPI (Indonesia)
2014-09-25T23:59:59.000Z
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, are discussed. The energy momentum tensor that is relevant to the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
Charmonium in strongly coupled quark-gluon plasma
Clint Young; Edward Shuryak
2008-09-22T23:59:59.000Z
The growing consensus that a strongly-coupled quark-gluon plasma (sQGP) has been observed at the SPS and RHIC experiments suggests a different framework for examining heavy quark dynamics. We present both semi-analytical treatment of Fokker-Planck (FP) evolution in pedagogical examples and numerical Langevin simulations of evolving charm quark-antiquark pairs on top of a hydrodynamically expanding fireball. In this way, we may conclude that the survival probability of bound charmonia states is greater than previously estimated, as the spatial equilibration of pairs proceeds through a ``slowly dissolving lump'' stage related to the pair interaction.
Onset of cavitation in the quark-gluon plasma
Mathis Habich; Paul Romatschke
2014-07-11T23:59:59.000Z
We study the onset of bubble formation (cavitation) in the quark-gluon plasma as a result of the reduction of the effective pressure from bulk-viscous corrections. By calculating velocity gradients in typical models for quark-gluon plasma evolution in heavy-ion collisions, we obtain results for the critical bulk viscosity above which cavitation occurs. Since present experimental data for heavy-ion collisions seems inconsistent with the presence of bubbles above the phase transition temperature of QCD, our results may be interpreted as an upper limit of the bulk viscosity in nature. Our results indicate that bubble formation is consistent with the expectation of hadronisation in low-temperature QCD.
Identifying the Charge Carriers of the Quark-Gluon Plasma
Scott Pratt
2012-03-20T23:59:59.000Z
Charge correlations in lattice gauge calculations suggest that up, down and strange charges move independently in the QGP (quark-gluon plasma), and that the density of such charges is similar to what is expected from simple thermal arguments. Here, we show how specific elements of the charge-charge correlation matrix in the QGP survive hadronization and become manifest in final-state charge-charge correlation measurements.
Thermal axion production in the primordial quark-gluon plasma
Graf, Peter; Steffen, Frank Daniel [Max-Planck-Institut fuer Physik, Foehringer Ring 6, D-80805 Munich (Germany)
2011-04-01T23:59:59.000Z
We calculate the rate for thermal production of axions via scattering of quarks and gluons in the primordial quark-gluon plasma. To obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling, we use systematic field theoretical methods such as hard thermal loop resummation and the Braaten-Yuan prescription. The thermally produced yield, the decoupling temperature, and the density parameter are computed for axions with a mass below 10 meV. In this regime, with a Peccei-Quinn scale above 6x10{sup 8} GeV, the associated axion population can still be relativistic today and can coexist with the axion cold dark matter condensate.
Thermal axion production in the primordial quark-gluon plasma
Peter Graf; Frank Daniel Steffen
2011-04-20T23:59:59.000Z
We calculate the rate for thermal production of axions via scattering of quarks and gluons in the primordial quark-gluon plasma. To obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling, we use systematic field theoretical methods such as hard thermal loop resummation and the Braaten-Yuan prescription. The thermally produced yield, the decoupling temperature, and the density parameter are computed for axions with a mass below 10 meV. In this regime, with a Peccei-Quinn scale above 6x10^8 GeV, the associated axion population can still be relativistic today and can coexist with the axion cold dark matter condensate.
Magnetic Component of Quark-Gluon Plasma
Jinfeng Liao; Edward Shuryak
2008-04-18T23:59:59.000Z
We describe recent developments of the "magnetic scenario" of sQGP. We show that at $T=(0.8-1.3)T_c$ there is a dense plasma of monopoles, capable of supporting metastable flux tubes. Their existence allows to quantitatively explained the non-trivial $T$-dependence of the static $\\bar Q Q$ potential energy calculated on the lattice. By molecular dynamics simulation we derived transport properties (shear viscosity and diffusion constant) and showed that the best liquid is given by most symmetric plasma, with 50%-50% of electric and magnetic charges. The results are close to those of the ``perfect liquid'' observed at RHIC.
Quarks Production in the Quark-Gluon Plasma Created in Relativistic Heavy Ion Collisions
Marco Ruggieri; Salvatore Plumari; Francesco Scardina; Vincenzo Greco
2015-02-16T23:59:59.000Z
In this article we report on our results about quark production and chemical equilibration of quark-gluon plasma. Our initial condition corresponds to a classic Yang-Mills spectrum, in which only gluon degrees of freedom are considered; the initial condition is then evolved to a quark-gluon plasma by means of relativistic transport theory with inelastic processes which permit the conversion of gluons to $q\\bar{q}$ pairs. We then compare our results to the ones obtained with a standard Glauber model initialization. We find that regardless of the initial condition the final stage of the system contains an abundant percentage of $q\\bar{q}$ pairs; moreover spanning the possible coupling from weak to strong we find that unless the coupling is unrealistically small, both production rate and final percentage of fermions is quite large.
Quarks Production in the Quark-Gluon Plasma Created in Relativistic Heavy Ion Collisions
Ruggieri, Marco; Scardina, Francesco; Greco, Vincenzo
2015-01-01T23:59:59.000Z
In this article we report on our results about quark production and chemical equilibration of quark-gluon plasma. Our initial condition corresponds to a classic Yang-Mills spectrum, in which only gluon degrees of freedom are considered; the initial condition is then evolved to a quark-gluon plasma by means of relativistic transport theory with inelastic processes which permit the conversion of gluons to $q\\bar{q}$ pairs. We then compare our results to the ones obtained with a standard Glauber model initialization. We find that regardless of the initial condition the final stage of the system contains an abundant percentage of $q\\bar{q}$ pairs; moreover spanning the possible coupling from weak to strong we find that unless the coupling is unrealistically small, both production rate and final percentage of fermions is quite large.
Mean Field Effects In The Quark-Gluon Plasma
Zhi Guang Tan; A. Bonasera
2006-11-20T23:59:59.000Z
A transport model based on the mean free path approach for an interacting meson system at finite temperatures is discussed. A transition to a quark gluon plasma is included within the framework of the MIT bag model. The results obtained compare very well with Lattice QCD calculations when we include a mean field in the QGP phase due to the Debye color screening. In particular the cross over to the QGP at about 175 MeV temperature is nicely reproduced. We also discuss a possible scenario for hadronization which is especially important for temperatures below the QGP phase transition.
Very high energy probes of the quark-gluon plasma
Ludlam, T.; Paige, F.; Madansky, L.
1984-01-01T23:59:59.000Z
Among the penetrating probes of nuclear matter the most frequently discussed have been those which involve the detection of photons or leptons with m/sub T/ approx. = P/sub T/ < 3 GeV. This is the expected range of emission from a hot, thermalized plasma of quarks and gluons. The suggestion has been made that in very high energy collisions of nuclei the properties of high P/sub T/ jets may also reflect the characteristics of the nuclear medium through which the parent partons have propagated just after the collision. In this note we expand on the possible uses of such a probe.
J/psi Production in Quark-Gluon Plasma
Li Yan; Pengfei Zhuang; Nu Xu
2006-11-05T23:59:59.000Z
We study J/psi production at RHIC and LHC energies with both initial production and regeneration. We solve the coupled set of transport equation for the J/psi distribution in phase space and the hydrodynamic equation for evolution of quark-gluon plasma. At RHIC, continuous regeneration is crucial for the J/psi momentum distribution while the elliptic flow is still dominated by initial production. At LHC energy, almost all the initially created J\\psis are dissociated in the medium and regeneration dominates the J/psi properties.
The Fluid Nature of Quark-Gluon Plasma
W. A. Zajc
2008-02-25T23:59:59.000Z
Collisions of heavy nuclei at very high energies offer the exciting possibility of experimentally exploring the phase transformation from hadronic to partonic degrees of freedom which is predicted to occur at several times normal nuclear density and/or for temperatures in excess of $\\sim 170$ MeV. Such a state, often referred to as a quark-gluon plasma, is thought to have been the dominant form of matter in the universe in the first few microseconds after the Big Bang. Data from the first five years of heavy ion collisions of Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) clearly demonstrate that these very high temperatures and densities have been achieved. While there are strong suggestions of the role of quark degrees of freedom in determining the final-state distributions of the produced matter, there is also compelling evidence that the matter does {\\em not} behave as a quasi-ideal state of free quarks and gluons. Rather, its behavior is that of a dense fluid with very low kinematic viscosity exhibiting strong hydrodynamic flow and nearly complete absorption of high momentum probes. The current status of the RHIC experimental studies is presented, with a special emphasis on the fluid properties of the created matter, which may in fact be the most perfect fluid ever studied in the laboratory.
Heavy quark collisional energy loss in the quark-gluon plasma including finite relaxation time
Mauro Elias; J. Peralta-Ramos; E. Calzetta
2014-07-12T23:59:59.000Z
In this paper, we calculate the soft-collisional energy loss of heavy quarks traversing the viscous quark-gluon plasma including the effects of a finite relaxation time $\\tau_\\pi$ on the energy loss. We find that the collisional energy loss depends appreciably on $\\tau_\\pi$ . In particular, for typical values of the viscosity-to-entropy ratio, we show that the energy loss obtained using $\\tau_\\pi$ = 0 can be $\\sim$ 10$\\%$ larger than the one obtained using $\\tau_\\pi$ = 0. Moreover, we find that the energy loss obtained using the kinetic theory expression for $\\tau_\\pi$ is much larger that the one obtained with the $\\tau_\\pi$ derived from the Anti de Sitter/Conformal Field Theory correspondence. Our results may be relevant in the modeling of heavy quark evolution through the quark-gluon plasma.
Chiral electric separation effect in the quark-gluon plasma
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Jiang, Yin; Liao, Jinfeng; Huang, Xu-Guang
2015-02-01T23:59:59.000Z
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient ??e, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=??e(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure ??e???5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density ?5 ? 0. Using the Hard-Thermal-Loop framework, the CESEmore »conductivity for the QGP is found to be ??e = (#)TTrfQeQA/g?ln(1/g) ??5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.« less
Chiral electric separation effect in the quark-gluon plasma
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Jiang, Yin [Indiana Univ., Bloomington, IN (United States); Liao, Jinfeng [Indiana Univ., Bloomington, IN (United States); Brookhaven National Lab., Upton, NY (United States); Huang, Xu-Guang [Fudan Univ., Shanghai (China)
2015-02-01T23:59:59.000Z
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient ??e, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current JA that is generated in response to an externally applied electric field eE: JA=??e(eE). Starting with a rather general argument in the kinetic theory framework, we show how a characteristic structure ??e???5 emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density ?5 ? 0. Using the Hard-Thermal-Loop framework, the CESE conductivity for the QGP is found to be ??e = (#)TTrfQeQA/g?ln(1/g) ??5/T² to the leading-log accuracy with the numerical constant (#) depending on favor content, e.g., (#)=14.5163 for u, d light flavors.
Chiral electric separation effect in the quark-gluon plasma
Yin Jiang; Xu-Guang Huang; Jinfeng Liao
2015-02-16T23:59:59.000Z
In this paper we introduce and compute a new transport coefficient for the quark-gluon plasma (QGP) at very high temperature. This new coefficient $\\sigma_{\\chi e}$, the CESE (Chiral Electric Separation Effect) conductivity, quantifies the amount of axial current $\\vec J_A$ that is generated in response to an externally applied electric field $e\\vec E$: $\\vec J_A = \\sigma_{\\chi e} (e\\vec E)$. Starting with rather general argument in the kinetic theory framework, we show how a characteristic structure $\\sigma_{\\chi e}\\propto \\mu \\mu_5$ emerges, which also indicates the CESE as an anomalous transport effect occurring only in a parity-odd environment with nonzero axial charge density $\\mu_5\
Thermalization of heavy quarks in the quark-gluon plasma
van Hees, H.; Rapp, Ralf.
2005-01-01T23:59:59.000Z
the kinetic equilibration of c quarks as compared to using perturbative interactions. We also comment on consequences for D-meson observables in ultrarelativistic heavy-ion collisions. DOI: 10.1103/PhysRevC.71.034907 PACS number(s): 12.38.Mh, 24.85.+p, 25... of individual c quarks in the QGP will reflect themselves in transverse- momentum (pT -) spectra of open charm hadrons (D mesons) [4?7], most notably their elliptic flow, v2(pT ), in semicentral collisions [8,9]. Preliminary experimental results from...
Thermalization of heavy quarks in the quark-gluon plasma
van Hees, H.; Rapp, Ralf.
2005-01-01T23:59:59.000Z
the BNL Relativistic Heavy-Ion Collider (RHIC) indicate the possibility that the D-meson v2 could be similar in magnitude to the one of light hadrons [10,11]. Since the c quark is rather heavy, this would be quite remarkable and could provide important... temperature) has been suggested as a mechanism to enhance partonic cross sections [12?14] to facilitate rapid thermalization of the bulk matter at RHIC as required in hy- drodynamical models. The notion of charmonium resonances in the QGP [15,16] has been...
Production, elliptic flow and energy loss of heavy quarks in the quark-gluon plasma
Jan Uphoff; Oliver Fochler; Zhe Xu; Carsten Greiner
2010-11-10T23:59:59.000Z
Production, elliptic flow and the nuclear modification factor of charm and bottom quarks are studied in central and non-central heavy-ion collisions at RHIC and LHC using the partonic transport model Boltzmann Approach of MultiParton Scatterings (BAMPS). Employing an initial heavy quark yield obtained with PYTHIA the full space-time evolution of charm and bottom quarks in the quark-gluon plasma (QGP) is carried out with BAMPS, taking also secondary production in the QGP into account. Only elastic collisions of heavy quarks with particles from the medium cannot describe the experimentally observed elliptic flow and nuclear modification factor. However, using an improved Debye screening and the running coupling yields a result which is much closer to data.
Virtual Photon Emission from Quark-Gluon Plasma
S. V. Suryanarayana
2007-04-28T23:59:59.000Z
We recently proposed an empirical approach for the Landau-Pomeranchuk-Migdal (LPM) effects in photon emission from the quark gluon plasma as a function of photon mass. This approach was based on Generalized Emission Functions (GEF) for photon emission, derived at a fixed temperature and strong coupling constant. In the present work, we have extended the LPM calculations for several temperatures and strong coupling strengths. The integral equations for (${\\bf \\tilde{f}(\\tilde{p}_\\perp)}$) and ($\\tilde{g}({\\bf \\tilde{p}_\\perp})$) are solved by the iterations method for the variable set \\{$p_0,q_0,Q^2,T,\\alpha_s$\\}, considering bremsstrahlung and $\\bf aws$ processes. We generalize the dynamical scaling variables, $x_T$, $x_L$, for bremsstrahlung and {\\bf aws} processes which are now functions of variables $p_0,q_0,Q^2,T,\\alpha_s$. The GEF introduced earlier, $g^b_T$, $g^a_T$, $g^b_L$, $g^a_L$, are also generalized for any temperatures and coupling strengths. From this, the imaginary part of the photon polarization tensor as a function of photon mass and energy can be calculated as a one dimensional integral over these GEF and parton distribution functions in the plasma. However, for phenomenological studies of experimental data, one needs a simple empirical formula without involving parton momentum integrations. Therefore, we present a phenomenological formula for imaginary photon polarization tensor as a function of \\{$q_0,Q^2,T,\\alpha_s$\\} that includes bremsstrahlung and $\\bf aws$ mechanisms along with LPM effects.
Jet conversions in a quark-gluon plasma
Liu, W.; Ko, Che Ming; Zhang, B. W.
2007-01-01T23:59:59.000Z
.75.?q One of the most interesting observations in central heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) is the suppressed production of hadrons with large transverse momentum [1,2]. This phenomenon has been attributed... transverse momentum pions at RHIC can indeed be described. Initial jet distributions and heavy ion collision dynamics. To see the effect of conversions between quark and gluon jets on their energy losses in QGP, we consider central Au+Au collisions...
Collisional energy loss of a fast heavy quark in a quark-gluon plasma
Stephane Peigne; Andre Peshier
2008-02-29T23:59:59.000Z
We discuss the average collisional energy loss dE/dx of a heavy quark crossing a quark-gluon plasma, in the limit of high quark energy E >> M^2/T, where M is the quark mass and T >> M is the plasma temperature. In the fixed coupling approximation, at leading order dE/dx \\propto \\alpha_s^2, with a coefficient which is logarithmically enhanced. The soft logarithm arising from t-channel scattering off thermal partons is well-known, but a collinear logarithm from u-channel exchange had previously been overlooked. We also determine the constant beyond those leading logarithms. We then generalize our calculation of dE/dx to the case of running coupling. We estimate the remaining theoretical uncertainty of dE/dx, which turns out to be quite large under RHIC conditions. Finally, we point out an approximate relation between dE/dx and the QCD Debye mass, from which we derive an upper bound to dE/dx for all quark energies.
Jet Quenching from soft QCD Scattering in the Quark-Gluon Plasma
Korinna Zapp; Gunnar Ingelman; Johan Rathsman; Johanna Stachel
2006-03-28T23:59:59.000Z
We show that partons traversing a quark-gluon plasma can lose substantial amounts of energy also by scatterings, and not only through medium-induced radiation as mainly considered previously. Results from Monte Carlo simulations of soft interactions of partons, emerging from a hard scattering, through multiple elastic scatterings on gluons in an expanding relativistic plasma show a sizeable jet quenching which can account for a substantial part of the effect observed in RHIC data.
Tomography of a quark gluon plasma at RHIC and LHC energies
P. B. Gossiaux; R. Bierkandt; J. Aichelin
2009-03-23T23:59:59.000Z
Using the recently published model for the collisional energy loss of heavy quarks (Q) in a Quark Gluon Plasma (QGP), based on perturbative QCD (pQCD) with a running coupling constant, we study the interaction between heavy quarks and plasma particles in detail. We discuss correlations between the simultaneously produced $c$ and $\\bar{c}$ quarks, study how central collisions can be experimentally selected, predict observable correlations and extend our model to the energy domain of the large hadron collider (LHC). We finally compare the predictions of our model with that of other approaches like AdS/CFT.
Dilepton as a Possible Signature for the Baryon-Rich Quark-Gluon Plasma
Xia, L. H.; Ko, Che Ming; Li, C. T.
1990-01-01T23:59:59.000Z
will be produced so that a transition from the hadronic matter to the quark-gluon plasma will take place. For future experi- ments at the proposed relativistic heavy-ion collider (RHIC) a baryon free quark-gluon plasma is expected to be created because..., it will not be considered as a definitive signature until a better understanding of the dissociation of J/4 by the hadronic particles is achieved. For experiments carried out at the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS) at 14.5 Ge...
Radiative energy loss of high energy quarks in finite-size nuclear matter and quark-gluon plasma
B. G. Zakharov
1997-04-07T23:59:59.000Z
The induced gluon radiation of a high energy quark in a finite-size QCD medium is studied. For a sufficiently energetic quark produced inside a medium we find the radiative energy loss $\\Delta E_{q}\\propto L^{2}$, where L is the distance passed by quark in the medium. It has a weak dependence on the initial quark energy $E_{q}$. The $L^{2}$ dependence turns to $L^{1}$ as the quark energy decreases. Numerical calculations are performed for a cold nuclear matter and a hot quark-gluon plasma. For a quark incident on a nucleus we predict $\\Delta E_{q}\\approx 0.1 E_{q}(L/10 fm)^{\\beta}$, with $\\beta$ close to unity.
What does it mean to have `seen' the quark-gluon plasma?
Scott Pratt
2012-10-01T23:59:59.000Z
Identifying the quark-gluon plasma requires convincing experimental evidence that partons move independently throughout the environment created in a heavy ion collision and with densities expected from equilibrium considerations. In lattice calculations, charge correlations suggest that quarks exist independently, and are not merely exchanged from hadronic object to another. Many experimental signatures (J/Psi suppression, quark number scaling, etc.) suggest that quarks are not confined to their original singlets, but these signatures do not make a clear case that quarks move independently or that they have the expected densities. I discuss a class of measurements that parallel lattice observables and has the prospect of investigating whether partonic charges move independently.
On the Energy Loss of High Energy Quarks in a Finite-Size Quark-Gluon Plasma
B. G. Zakharov
2000-12-28T23:59:59.000Z
We study within the light-cone path integral approach the induced gluon emission from a fast quark passing through a finite-size QCD plasma. We show that the leading log approximation used in previous studies fails when the gluon formation length becomes of the order of the length of the medium traversed by the quark. Calculation of the energy loss beyond the leading log approximation gives the energy loss which grows logarithmically with quark energy contrary to the energy independent prediction of the leading log approximation.
Dilepton emission at temperature dependent baryonic quark-gluon plasma
S. Somorendro Singh; Yogesh Kumar
2012-08-04T23:59:59.000Z
A fireball of QGP is evoluted at temperature dependent chemical potential by a statistical model in the pionic medium. We study the dilepton emission rate at temperature dependent chemical potential (TDCP) from such a fireball of QGP. In this model, we take the dynamical quark mass as a finite value dependence on temparature and parametrization factor of the QGP evolution. The temperature and factor in quark mass enhance in the growth of the droplets as well as in the dilepton emission rates. The emission rate from the plasma shows dilepton spectrum in the intermediate mass region (IMR) of (1.0-4.0) GeV and its rate is observed to be a strong increasing function of the temperature dependent chemical potential for quark and antiquark annihilation.
Chiral Magnetic Effect in the Anisotropic Quark-Gluon Plasma
Mohammad Ali-Akbari; Seyed Farid Taghavi
2014-08-27T23:59:59.000Z
An anisotropic thermal plasma phase of a strongly coupled gauge theory can be holographically modelled by an anisotropic AdS black hole. The temperature and anisotropy parameter of the AdS black hole background of interest [1] is specified by the location of the horizon and the value of the Dilaton field at the horizon. Interestingly, for the first time, we obtain two functions for the values of the horizon and Dilaton field in terms of the temperature and anisotropy parameter. Then by introducing a number of spinning probe D7-branes in the anisotropic background, we compute the value of the chiral magnetic effect (CME). We observe that in the isotropic and anisotropic plasma the value of the CME is equal for the massless quarks. However, at fixed temperature, raising the anisotropy in the system will increase the value of the CME for the massive quarks.
Search and study of Quark Gluon Plasma at the CERN-LHC
Tapan Nayak; Bikash Sinha
2009-04-22T23:59:59.000Z
The major aim of nucleus-nucleus collisions at the LHC is to study the physics of strongly interacting matter and the quark gluon plasma (QGP), formed in extreme conditions of temperature and energy density. We give a brief overview of the experimental program and discuss the signatures and observables for a detailed study of QGP matter.
High-energy dileptons from an anisotropic quark-gluon plasma
Mauricio Martinez
2009-11-10T23:59:59.000Z
We calculate leading-order dilepton yields from a quark-gluon plasma which has a time-dependent anisotropy in momentum space. Such anisotropies can arise during the earliest stages of quark-gluon plasma evolution due to the rapid longitudinal expansion of the created matter. A phenomenological model for the proper time dependence of the parton hard momentum scale, p_hard, and the plasma anisotropy parameter, xi, is proposed. The model describes the transition of the plasma from a 0+1 dimensional collisionally-broadened expansion at early times to a 0+1 dimensional ideal hydrodynamic expansion at late times. We find that high-energy dilepton production is enhanced by pre-equilibrium emission up to 50% at LHC energies, if one assumes an isotropization/thermalization time of 2 fm/c. Given sufficiently precise experimental data this enhancement could be used to determine the plasma isotropization time experimentally.
Moritz Greif; Ioannis Bouras; Zhe Xu; Carsten Greiner
2014-11-17T23:59:59.000Z
Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative $2\\leftrightarrow 3$ perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.
A New Phase of Matter: Quark-Gluon Plasma Beyond the Hagedorn Critical Temperature
Müller, Berndt
2015-01-01T23:59:59.000Z
I retrace the developments from Hagedorn's concept of a limiting temperature for hadronic matter to the discovery and characterization of the quark-gluon plasma as a new state of matter. My recollections begin with the transformation more than 30 years ago of Hagedorn's original concept into its modern interpretation as the "critical" temperature separating the hadron gas and quark-gluon plasma phases of strongly interacting matter. This was followed by the realization that the QCD phase transformation could be studied experimentally in high-energy nuclear collisions. I describe here my personal effort to help develop the strangeness experimental signatures of quark and gluon deconfinement and recall how the experimental program proceeded soon to investigate this idea, at first at the SPS, then at RHIC, and finally at LHC. As it is often the case, the experiment finds more than theory predicts, and I highlight the discovery of the "perfectly" liquid quark-gluon plasma at RHIC. I conclude with an outline of fu...
Radiative parton energy loss in expanding quark-gluon plasma with magnetic monopoles
B. G. Zakharov
2014-12-19T23:59:59.000Z
We study radiative parton energy loss in an expanding quark-gluon plasma with magnetic monopoles. We find that for realistic number density of thermal monopoles obtained in lattice simulations parton rescatterings on monopoles can considerably enhance energy loss for plasma produced in $AA$ collisions at RHIC and LHC energies. However, contrary to previous expectations, monopoles do not lead to the surface dominance of energy loss.
N. N. Guan; Z. J. He; J. L. Long; X. Z. Cai; Y. G. Ma; J. W. Li; W. Q. Shen
2009-09-02T23:59:59.000Z
By considering the effect of shear viscosity we have investigated the evolution of a chemically equilibrating quark-gluon plasma at finite baryon density. Based on the evolution of the system we have performed a complete calculation for the dilepton production from the following processes: $q\\bar{q}{\\to}l\\bar{l}$, $q\\bar{q}{\\to}gl\\bar{l}$, Compton-like scattering ($qg{\\to}ql\\bar{l}$, $\\bar{q}g{\\to}{\\bar{q}}l\\bar{l}$), gluon fusion $g\\bar{g}{\\to}c\\bar{c}$, annihilation $q\\bar{q}{\\to}c\\bar{c}$ as well as the multiple scattering of quarks. We have found that quark-antiquark annihilation, Compton-like scatterring, gluon fusion, and multiple scattering of quarks give important contributions. Moreover, we have also found that the dilepton yield is an increasing function of the initial quark chemical potential, and the increase of the quark phase lifetime because of the viscosity also obviously raises the dilepton yield.
Anti pp searches for quark-gluon plasma at TeV I
Turkot, F.
1986-06-01T23:59:59.000Z
Three experiments that have been approved to run at TeV I are discussed from the viewpoint of their capability to search for evidence of the QCD phase transition in proton-antiproton collisions at 1.6 TeV. One of these experiments, E-735, was proposed as a dedicated search for quark-gluon plasma effects with a detector designed to study large total E/sub T/, low P/sub T/ individual particles. The other two, E-741 (CDF) and E-740 (DO), embody general purpose four-pi detectors designed primarily to study the physics of W and Z bosons and other large P/sub T/ phenomena. The detectors and their quark-gluon plasma signals are compared. 8 refs., 6 figs., 4 tabs. (LEW)
Spatially Modulated Phase in the Holographic Description of Quark-Gluon Plasma
Ooguri, Hirosi [California Institute of Technology, 452-48, Pasadena, California 91125 (United States); Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8586 (Japan); Park, Chang-Soon [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, California 95064 (United States)
2011-02-11T23:59:59.000Z
We present a string theory construction of a gravity dual of a spatially modulated phase. Our earlier work shows that the Chern-Simons term in the five-dimensional Maxwell theory destabilizes the Reissner-Nordstroem black holes in anti-de Sitter space if the Chern-Simons coupling is sufficiently high. In this Letter, we show that a similar instability is realized on the world volume of 8-branes in the Sakai-Sugimoto model in the quark-gluon plasma phase. Our result suggests a new spatially modulated phase in quark-gluon plasma when the baryon density is above 0.8N{sub f} fm{sup -3} at temperature 150 MeV.
pp, pA and. cap alpha cap alpha. collisions and the understanding of the quark-gluon plasma
Geist, W.M.
1988-06-01T23:59:59.000Z
Global characteristics of heavy ion collisions at high energy are now understood at some level such that the challenging search for Quark-Gluon plasma signatures becomes of more importance. Some features of pp, pA, and ..cap alpha../ alpha/ interactions at ..sqrt..s less than or equal to 62 GeV are selected to illustrate potential consequences for, and problems of, investigations of the Quark-Gluon plasma. 35 refs., 8 figs.
Effect of running coupling on photon emission from quark gluon plasma
Mahatsab Mandal; Sukanya Mitra; Pradip Roy; Sourav Sarkar
2012-06-22T23:59:59.000Z
We discuss the role of running coupling on the thermal photon yield from quark gluon plasma. It is shown that the photon production rate from the partonic phase is considerably enhanced when running coupling is considered with respect to a fixed value. However, we show by explicit evaluation that although this difference survives the space-time evolution the experimental data cannot distinguish between the two once the hard contribution, which is an essential component of photon production mechanism, is added.
Dilepton as a Possible Signature for the Baryon-Rich Quark-Gluon Plasma
Xia, L. H.; Ko, Che Ming; Li, C. T.
1990-01-01T23:59:59.000Z
of dileptons at small invariant masses. This effect becomes more pro- nounced as the density of the hadronic matter increases. On the other hand, if a baryon-rich quark-gluon plasma is initially formed, then dileptons will be produced from the qq... reasonable approximation as the process qq~gg is fast. As in the consideration of the phase dia- gram, we shall also neglect strange quark production in the fireball. This will not change our results appreciably as it has been shown in Ref. 11...
Heavy quark production from jet conversions in a quark-gluon plasma
Liu, W.; Fries, Rainer J.
2008-01-01T23:59:59.000Z
/BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973, USA (Received 13 May 2008; published 12 September 2008) Recently, it has been demonstrated that the chemical composition of jets in heavy ion collisions is significantly altered... observables that could be measured at the Relativistic Heavy Ion Collider (RHIC) or the Large Hadron Collider (LHC) [14]. In Ref. [12] it was found that conversions of light quarks to gluons could help solve the puzzle of very similar nuclear modification...
The sound generated by a fast parton in the quark-gluon plasma is a crescendo
R. B. Neufeld; B. Muller
2009-09-21T23:59:59.000Z
The total energy deposited into the medium per unit length by a fast parton traversing a quark-gluon plasma is calculated. We take the medium excitation due to collisions to be given by the well known expression for the collisional drag force. The parton's radiative energy loss contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. In our model, this leads to a length dependence on the differential energy loss due to the interactions of radiated gluons with the medium. The final result, which is a sum of the primary and the secondary contributions, is then treated as the coefficient of a local hydrodynamic source term. Results are presented for energy density wave induced by two fast, back-to-back partons created in an initial hard interaction.
Transport properties of the quark-gluon plasma from lattice QCD
Harvey B. Meyer
2009-09-10T23:59:59.000Z
I review the progress made in extracting transport properties of the quark-gluon plasma from lattice QCD simulations. The information on shear and bulk viscosity, the "low-energy constants" of hydrodynamics, is encoded in the retarded correlators of Tmunu, the energy-momentum tensor. Euclidean correlators, computable on the lattice, are related to the retarded correlators by an integral transform. The most promising strategy to extract shear and bulk viscosity is to study the shear and sound channel correlators where the hydrodynamic modes dominate. I present preliminary results from a comprehensive study of the gluonic plasma between 0.95Tc and 4.0Tc.
Exciting the quark-gluon plasma with a relativistic jet
Massimo Mannarelli; Cristina Manuel
2007-06-27T23:59:59.000Z
We discuss the properties of a system composed by a static plasma traversed by a jet of particles. Assuming that both the jet and the plasma can be described using a hydrodynamical approach, and in the conformal limit, we find that unstable modes arise when the velocity of the jet is larger than the speed of the sound of the plasma and only modes with momenta smaller than a certain values are unstable. Moreover, for ultrarelativistic velocities of the jet the most unstable modes correspond to relative angles between the velocity of the jet and momentum of the collective mode ~ pi/4. Our results suggest an alternative mechanism for the description of the jet quenching phenomenon, where the jet crossing the plasma loses energy exciting colored unstable modes. In LHC this effect should be seen with an enhanced production of hadrons for some specific values of their momenta and in certain directions of momenta space.
Thermal charm production in a quark-gluon plasma in Pb-Pb collisions at root S(NN)=5.5 TeV
Zhang, Ben-Wei; Ko, Che Ming; Liu, Wei.
2008-01-01T23:59:59.000Z
an extended volume of quark-gluon plasma (QGP). Experiments at the Relativistic Heavy Ion Collider (RHIC) have indeed shown that the results are consistent with the formation of a strongly interacting quark-gluon plasma during the initial stage... survive in the quark-gluon plasma at temperatures up to about twice the deconfinement temperature [6,7], J/? production in relativistic heavy ion collisions may still be suppressed in heavy ion collisions at RHIC [8?10]. However, if the initial...
Jet energy loss in the quark-gluon plasma by stream instabilities
Massimo Mannarelli; Cristina Manuel; Sergi Gonzalez-Solis; Michael Strickland
2009-12-01T23:59:59.000Z
We study the evolution of the plasma instabilities induced by two jets of particles propagating in opposite directions and crossing a thermally equilibrated non-Abelian plasma. In order to simplify the analysis we assume that the two jets of partons can be described with uniform distribution functions in coordinate space and by Gaussian distribution functions in momentum space. We find that while crossing the quark-gluon plasma, the jets of particles excite unstable chromomagnetic and chromoelectric modes. These fields interact with the particles (or hard modes) of the plasma inducing the production of currents; thus, the energy lost by the jets is absorbed by both the gauge fields and the hard modes of the plasma. We compare the outcome of the numerical simulations with the analytical calculation performed assuming that the jets of particles can be described by a tsunami-like distribution function. We find qualitative and semi-quantitative agreement between the results obtained with the two methods.
Jet energy loss in the quark-gluon plasma by stream instabilities
Mannarelli, Massimo; Gonzalez-Solis, Sergi; Strickland, Michael
2009-01-01T23:59:59.000Z
We study the evolution of the plasma instabilities induced by two jets of particles propagating in opposite directions and crossing a thermally equilibrated non-Abelian plasma. In order to simplify the analysis we assume that the two jets of partons can be described with uniform distribution functions in coordinate space and by Gaussian distribution functions in momentum space. We find that while crossing the quark-gluon plasma, the jets of particles excite unstable chromomagnetic and chromoelectric modes. These fields interact with the particles (or hard modes) of the plasma inducing the production of currents; thus, the energy lost by the jets is absorbed by both the gauge fields and the hard modes of the plasma. We compare the outcome of the numerical simulations with the analytical calculation performed assuming that the jets of particles can be described by a tsunami-like distribution function. We find qualitative and semi-quantitative agreement between the results obtained with the two methods.
Effects of the Running of the QCD Coupling on the Energy Loss in the Quark-Gluon Plasma
Jens Braun; Hans-Jürgen Pirner
2006-10-25T23:59:59.000Z
Finite temperature modifies the running of the QCD coupling alpha_s(k,T) with resolution k. After calculating the thermal quark and gluon masses selfconsistently, we determine the quark-quark and quark-gluon cross sections in the plasma based on the running coupling. We find that the running coupling enhances these cross sections by factors of two to four depending on the temperature. We also compute the energy loss dE/dx of a high-energy quark in the plasma as a function of temperature. Our study suggests that, beside t-channel processes, inverse Compton scattering is a relevant process for a quantitative understanding of the energy loss of an incident quark in a hot plasma.
Effects of the running of the QCD coupling on the energy loss in the quark-gluon plasma
Braun, Jens [Institute for Theoretical Physics, University of Heidelberg, Philosophenweg 19, 69120 Heidelberg (Germany); Pirner, Hans-Juergen [Institute for Theoretical Physics, University of Heidelberg, Philosophenweg 19, 69120 Heidelberg (Germany); Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)
2007-03-01T23:59:59.000Z
Finite temperature modifies the running of the QCD coupling {alpha}{sub s}(k,T) with resolution k. After calculating the thermal quark and gluon masses self-consistently, we determine the quark-quark and quark-gluon cross sections in the plasma based on the running coupling. We find that the running coupling enhances these cross sections by factors of two to four depending on the temperature. We also compute the energy loss (dE/dx) of a high-energy quark in the plasma as a function of temperature. Our study suggests that, beside t-channel processes, inverse Compton scattering is a relevant process for a quantitative understanding of the energy loss of an incident quark in a hot plasma.
QCD Collisional Energy Loss in an Increasingly Interacting Quark Gluon Plasma
M. B. Gay Ducati; V. P. Goncalves; L. F. Mackedanz
2007-05-02T23:59:59.000Z
The discovery of the jet quenching in central Au + Au collisions at the Relativistic Heavy-ion Collider (RHIC) at Brookhaven National Laboratory has provided clear evidence for the formation of strongly interacting dense matter. It has been predicted to occur due to the energy loss of high energy partons that propagate through the quark gluon plasma. In this paper we investigate the dependence of the parton energy loss due to elastic scatterings in a parton plasma on the value of the strong coupling and its running with the evolution of the system. We analyze different prescriptions for the QCD coupling and calculate the energy and length dependence of the fractional energy loss. Moreover, the partonic quenching factor for light and heavy quarks is estimated. We found that the predicted enhancement of the heavy to light hadrons ($D/\\pi$) ratio is strongly dependent on the running of the QCD coupling constant.
Collinear Photon Emission from the Quark-Gluon Plasma: The Light-Cone Path Integral Formulation
P. Aurenche; B. G. Zakharov
2006-12-27T23:59:59.000Z
We give a simple physical derivation of the photon emission rate from the weakly coupled quark-gluon plasma connected with the collinear processes $q\\to \\gamma q$ and $q\\bar{q}\\to \\gamma$. The analysis is based on the light-cone path integral approach to the induced radiation. Our results agree with that by Arnold, Moore and Yaffe obtained using the real-time thermal perturbation theory. It is demonstrated that the solution of the AMY integral equation is nothing but the time-integrated Green's function of the light-cone path integral approach written in the momentum representation.
Energy Loss of Gluons, Baryons and k-Quarks in an N=4 SYM Plasma
Mariano Chernicoff; Alberto Guijosa
2007-02-08T23:59:59.000Z
We consider different types of external color sources that move through a strongly-coupled thermal N=4 super-Yang-Mills plasma, and calculate, via the AdS/CFT correspondence, the dissipative force (or equivalently, the rate of energy loss) they experience. A bound state of k quarks in the totally antisymmetric representation is found to feel a force with a nontrivial k-dependence. Our result for k=1 (or k=N-1) agrees at large N with the one obtained recently by Herzog et al. and Gubser, but contains in addition an infinite series of 1/N corrections. The baryon (k=N) is seen to experience no drag. Finally, a heavy gluon is found to be subject to a force which at large N is twice as large as the one experienced by a heavy quark, in accordance with gauge theory expectations.
Generalized Emission Functions for Photon Emission from Quark-Gluon Plasma
S. V. Suryanarayana
2006-06-06T23:59:59.000Z
The Landau-Pomeranchuk-Migdal effects on photon emission from the quark gluon plasma have been studied as a function of photon mass, at a fixed temperature of the plasma. The integral equations for the transverse vector function (${\\bf \\tilde{f}(\\tilde{p}_\\perp)}$) and the longitudinal function ($\\tilde{g}({\\bf \\tilde{p}_\\perp})$) consisting of multiple scattering effects are solved by the self consistent iterations method and also by the variational method for the variable set \\{$p_0,q_0,Q^2$\\}, considering the bremsstrahlung and the $\\bf aws$ processes. We define four new dynamical scaling variables, $x^b_T$,$x^a_T$,$x^b_L$,$x^a_L$ for bremsstrahlung and {\\bf aws} processes and analyse the transverse and longitudinal components as a function of \\{$p_0,q_0,Q^2$\\}. We generalize the concept of photon emission function and we define four new emission functions for massive photon emission represented by $g^b_T$, $g^a_T$, $g^b_L$, $g^a_L$. These have been constructed using the exact numerical solutions of the integral equations. These four emission functions have been parameterized by suitable simple empirical fits. In terms of these empirical emission functions, the virtual photon emission from quark gluon plasma reduces to one dimensional integrals that involve folding over the empirical $g^{b,a}_{T,L}$ functions with appropriate quark distribution functions and the kinematic factors. Using this empirical emission functions, we calculated the imaginary part of the photon polarization tensor as a function of photon mass and energy.
Jet-induced gauge field instabilities in the quark-gluon plasma
Massimo Mannarelli; Cristina Manuel
2008-05-23T23:59:59.000Z
We discuss the properties of the collective modes of a system composed by a thermalized quark-gluon plasma traversed by a relativistic jet of partons. The transport equations obeyed by the components of the plasma and of the jet are studied in the Vlasov approximation. Assuming that the partons in the jet can be described with a tsunami-like distribution function we derive the expressions of the dispersion law of the collective modes. Then the behavior of the unstable gauge modes of the system is analyzed for various values of the velocity of the jet, of the momentum of the collective modes and of the angle between these two quantities. We find that the most unstable modes are those with momentum orthogonal to the velocity of the jet, and the effect is stronger for ultrarelativistic jet velocities. Our results suggest a new possible collective mechanism for the description of the jet quenching phenomena in heavy ion collisions.
Shear viscosity $?$ to electric conductivity $?_{el}$ ratio for the Quark-Gluon Plasma
A. Puglisi; S. Plumari; V. Greco
2014-07-09T23:59:59.000Z
The transport coefficients of strongly interacting matter are currently subject of intense theoretical and phenomenological studies due to their relevance for the characterization of the quark-gluon plasma produced in ultra-relativistic heavy-ion collisions (uRHIC). We discuss the connection between the shear viscosity to entropy density ratio, $\\eta/s$, and the electric conductivity, $\\sigma_{el}$. We note that once the relaxation time is tuned to determine the shear viscosity $\\eta$ to have a minimum value $\\eta/s=1/4\\pi$ near the critical temperature $T_c$, one simultaneously predicts an electric conductivity $\\sigma_{el}/T$ very close to recent lQCD data. More generally, we discuss why the ratio of $\\eta/s$ over $\\sigma_{el}/T$ supplies a measure of the quark to gluon scattering rates whose knowledge would allow to significantly advance in the understanding of the QGP phase. We also predict that $(\\eta/s)/(\\sigma_{el}/T)$, independently on the running coupling $\\alpha_s(T)$, should increase up to about $\\sim 50$ for $T \\rightarrow T_c$, while it goes down to a nearly flat behavior around $\\simeq 3$ for $T \\geq 4\\, T_c$.
Bag model of hadrons, dual QCD thermodynamics and Quark-Gluon Plasma
H. C. Chandola; Garima Punetha; H. Dehnen
2015-05-16T23:59:59.000Z
Using the grand canonical ensemble formulation of a multi-particle statistical system, the thermodynamical description of the dual QCD has been presented in terms of the bag model of hadrons and analyzed for the quark-gluon plasma phase of hadronic matter. The dual QCD bag construction has been shown to lead to the radial pressure on the bag surface in terms of the vector glueball masses of the magnetically condensed QCD vacuum. Constructing the grand canonical partition function to deal with the quark-gluon plasma phase of the non-strange hadrons, the energy density and the plasma pressure have been derived and used to understand the dynamics of the associated phase transition. The critical temperature for QGP-hadron phase transition has been derived and numerically estimated by using various thermodynamic considerations. A comparison of the values of the critical temperatures for QGP-hadron phase transition with those obtained for the deconfinement-phase transition, has been shown to lead to the relaxation of the system via a mixed phase of QGP and hot hadron gas. The associated profiles of the normalized energy density and the specific heat have been shown to lead to a huge latent heat generation and indicate the onset of a first-order QGP phase transition. The squared speed of sound has been shown to act as a physical measure of large thermodynamical fluctuations near transition point where it shows a large reduction in its value as compared to the conformal limit and has intimate connection with the evolution of fire-ball and QGP in heavy-ion collision events. The possible implications of the trace anomaly and conformal measure on QGP formation have been discussed and a considerable increase in the degrees of freedom and the associated interaction effects has been indicated around the transition region and discussed for its relevance with the modern heavy-ion collision experiments.
Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Yin, Yi
2014-10-01T23:59:59.000Z
I extract the electrical conductivity ?0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v?, based on the thermal photon spectrum at 0.4GeVmore »Collaboration, I found that the electrical conductivity at QGP temperature is in the range: 0.4« less
Quark-gluon plasma in the early Universe and in ultra-relativistic heavy-ion collisions
Greco, V. [Department of Physics and Astronomy, University of Catania, Catania, Italy and INFN - Laboratori Nazionali del Sud, Catania (Italy)
2014-05-09T23:59:59.000Z
We briefly give an elementary introduction to the expansion of the Early Universe till when the phase transition of the quark-gluon plasma to a hadronic matter takes place. Then we describe some main element of the study of QGP by mean of ultra-relativistic heavy-ion collisions (uRHIC's)
Chiral vortical wave and induced flavor charge transport in a rotating quark-gluon plasma
Jiang, Yin; Liao, Jinfeng
2015-01-01T23:59:59.000Z
We show the existence of a new gapless collective excitation in a rotating fluid system with chiral fermions, named as the Chiral Vortical Wave (CVW). The CVW has its microscopic origin at the quantum anomaly and macroscopically arises from interplay between vector and axial charge fluctuations induced by vortical effects. The wave equation is obtained both from hydrodynamic current equations and from chiral kinetic theory and its solutions show nontrivial CVW-induced charge transport from different initial conditions. Using the rotating quark-gluon plasma in heavy ion collisions as a concrete example, we show the formation of induced flavor quadrupole in QGP and estimate the elliptic flow splitting effect for Lambda baryons that may be experimentally measured.
Resonance recombination model and quark distribution functions in the quark-gluon plasma
Ravagli, L.; van Hees, H.; Rapp, Ralf.
2009-01-01T23:59:59.000Z
observed constituent quark number scaling (CQNS) at the Relativistic Heavy Ion Collider (RHIC). To address this problem we combine our earlier developed quark recombination model with quark phase-space distributions computed from relativistic Langevin...
A T-Matrix Approach to Heavy Quark Interaction with Thermal Gluons in a Quark Gluon Plasma
Huggins, Kyle
2012-10-19T23:59:59.000Z
: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 51 viii LIST OF FIGURES FIGURE Page 2.1 In-medium HQ free and internal energies determined using lattice data [12] in the triplet (solid lines), sextet (dotted lines), and 15-plet (dashed lines) channels at temperatures T = 1:2Tc (left) and 2Tc...) for charm-gluon at 1:2Tc (thick) and 2:0Tc (thin). Diagrams illustrate the s-wave (left) and p-wave (right) for charm-gluon in potential U for the triplet (top), sextet (2nd row), and 15-plet (3rd row) color channels. The bottom diagram corresponds...
Resummation of Jet Shapes and Extracting Properties of the Quark-Gluon Plasma
Yang-Ting Chien
2014-11-04T23:59:59.000Z
Understanding the properties of the quark-gluon plasma (QGP) that is produced in ultra-relativistic nucleus-nucleus collisions has been one of the top priorities of the heavy ion program at the LHC. Energetic jets are produced and subsequently quenched in the collisions. Such jet quenching phenomena provide promising tools to probe the medium properties by studying the modification of jets due to the medium interactions. Significant modifications of jet shapes have been measured. In this talk we focus on the calculation of jet shapes in both proton-proton and lead-lead collisions using soft-collinear effective theory (SCET), with Glauber gluon interactions in the medium. Large logarithms in jet shapes are resummed at next-to-leading logarithmic (NLL) accuracy by the renormalization-group evolution between hierarchical jet scales. The medium interactions contribute as power corrections, and we calculate the modification of jet shapes at leading order in opacity with the static QGP model. Preliminary results are presented with good agreement with the recent CMS jet shape measurements.
Polymer Chains and Baryons in a Strongly Coupled Quark-Gluon Plasma
Jinfeng Liao; Edward V. Shuryak
2005-11-03T23:59:59.000Z
Recently there was a significant change of views on physical properties and underlying dynamics of Quark-Gluon Plasma at $T=170-350 MeV$, produced in heavy ion collisions at RHIC. Instead of being a gas of $q,g$ quasiparticles, a near-perfect liquid is observed. Also, precisely in this temperature interval, the interaction deduced from lattice studies is strong enough to support multiple binary bound states. This work is the first variational study of {\\em multibody} bound states. We will consider: (i) ``polymer chains'' of the type $\\bar q g g ..g q$; (ii) baryons $(qqq)$; (iii) closed (3-)chains of gluons $(ggg)$. We found that chains (i) form in exactly the same $T$ range as binary states, with the same binding {\\em per bond}. The binding and $T$-range for diquarks, baryons and closed 3-chains are also established. We point out that the presence of chains, or possibly even a chain network, may drastically change the transport properties of matter, such as charm diffusion or jet energy loss. We further suggest that it seems to exist only for $T=(1-1.5)T_c$ and thus there may be a ``latent period'' for charm/jet quenching in RHIC collisions, while matter cools down to such $T$.
Jet-induced gauge field instabilities in the quark-gluon plasma: A kinetic theory approach
Massimo Mannarelli; Cristina Manuel
2007-07-26T23:59:59.000Z
We discuss the properties of the collective modes of a system composed by a thermalized quark-gluon plasma traversed by a relativistic jet of partons. The transport equations obeyed by the components of the plasma and of the jet are studied in the Vlasov approximation. Assuming that the partons in the jet can be described with a tsunami-like distribution function we derive the expressions of the dispersion law of the collective modes. Then the behavior of the unstable gauge modes of the system is analyzed for various values of the velocity of the jet, of the momentum of the collective modes and of the angle between these two quantities. We find that the most unstable modes are those with momentum orthogonal to the velocity of the jet and that these instabilities appear when the velocity of the jet is higher than a threshold value, which depends on the plasma and jet frequencies. The results obtained within the Vlasov approximation are compared with the corresponding results obtained using a chromohydrodynamical approach.The effect we discuss here suggests a possible collective mechanism for the description of the jet quenching phenomena in heavy ion collisions.
Recent Results on Hard Probes of the Quark-Gluon Plasma with the ATLAS Experiment at the LHC
Kosek, Tomas; The ATLAS collaboration
2015-01-01T23:59:59.000Z
Jets provide a powerful tool for probing the dynamics of the quark-gluon plasma created in Pb+Pb collisions at the LHC. The modification of high-pT parton showers as they propagate in the quark-gluon plasma, often referred to as "jet quenching", provides insight on the short-distance dynamics of the plasma. Jet quenching has been observed in a variety of single jet, dijet, and photon-jet measurements at the LHC as well as in measurements of modified production of charged-particle These results will be presented along with a survey of results of control measurements in Pb+Pb and p+Pb collisions including electroweak final states.
Resonance recombination model and quark distribution functions in the quark-gluon plasma
Ravagli, L.; van Hees, H.; Rapp, Ralf.
2009-01-01T23:59:59.000Z
We investigate the consequences of space-momentum correlations in quark phase-space distributions for coalescence processes at the hadronization transition. Thus far it has been proved difficult to reconcile such correlations with the empirically...
Shear viscosity of the quark-gluon plasma in a kinetic theory approach
Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V. [Department of Physics and Astronomy, University of Catania, Via S. Sofia 64, I-95125 Catania, Italy and Laboratorio Nazionale del Sud, INFN-LNS, Via S. Sofia 63, I-95125 Catania (Italy)
2014-05-09T23:59:59.000Z
One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound ?/s=1/4? for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed ?/s and have a comparison with physical observables like elliptic flow.
Dynamical evolution of the chiral magnetic effect: applications to the quark-gluon plasma
Cristina Manuel; Juan M. Torres-Rincon
2015-01-29T23:59:59.000Z
We study the dynamical evolution of the so-called chiral magnetic effect in an electromagnetic conductor. To this end, we consider the coupled set of corresponding Maxwell and chiral anomaly equations, and we prove that these can be derived from chiral kinetic theory. After integrating the chiral anomaly equation over space in a closed volume, it leads to a quantum conservation law of the total helicity of the system. A change in the magnetic helicity density comes together with a modification of the chiral fermion density. We study in Fourier space the coupled set of anomalous equations and we obtain the dynamical evolution of the magnetic fields, magnetic helicity density, and chiral fermion imbalance. Depending on the initial conditions we observe how the helicity might be transferred from the fermions to the magnetic fields, or vice versa, and find that the rate of this transfer also depends on the scale of wavelengths of the gauge fields in consideration. We then focus our attention on the quark-gluon plasma phase, and analyze the dynamical evolution of the chiral magnetic effect in a very simple toy model. We conclude that an existing chiral fermion imbalance in peripheral heavy ion collisions would affect the magnetic field dynamics, and consequently, the charge dependent correlations measured in these experiments.
Quarkonia and heavy-quark relaxation times in the quark-gluon plasma
Riek, F.; Rapp, Ralf.
2010-01-01T23:59:59.000Z
and heavy-quark diffusion on a common basis and thus to obtain mutual constraints. The two-body interaction kernel is approximated within a potential picture for spacelike momentum transfers. An effective field-theoretical model combining color-Coulomb...
Quark spectral density and a strongly-coupled quark-gluon plasma.
Qin, S.; Chang, L.; Liu, Y.; Roberts, C. D. (Physics); (Peking Univ.); (Inst. of Applied Physics and Computational Mathematics); (National Lab. of Heavy Ion Accelerator)
2011-07-13T23:59:59.000Z
The maximum entropy method is used to compute the dressed-quark spectral density from the self-consistent numerical solution of a rainbow truncation of QCD's gap equation at temperatures above that for which chiral symmetry is restored. In addition to the normal and plasmino modes, the spectral function also exhibits an essentially nonperturbative zero mode for temperatures extending to 1.4-1.8 times the critical temperature, T{sub c}. In the neighborhood of T{sub c}, this long-wavelength mode contains the bulk of the spectral strength and as long as this mode persists, the system may fairly be described as a strongly-coupled state of matter.
Perfect Fluidity of the Quark Gluon Plasma Core as Seen through its Dissipative Hadronic Corona
Tetsufumi Hirano; Miklos Gyulassy
2006-03-08T23:59:59.000Z
The agreement of hydrodynamic predictions of differential elliptic flow and radial flow patterns with Au+Au data is one of the main lines of evidence suggesting the nearly perfect fluid properties of the strongly coupled Quark Gluon Plasma, sQGP, produced at RHIC. We study the sensitivity of this conclusion to different hydrodynamic assumptions on chemical and thermal freezeout after the sQGP hadronizes. We show that if chemical freezeout occurs at the hadronization time, the differential elliptic flow for pions increase with proper time in the late hadronic phase until thermal freezeout and leads to a discrepancy with the data. In contrast, if both chemical and thermal equilibrium are maintained past the hadronization, then the mean pT per pion increases in a way that accidentally preserves v2(pT) from the sQGP phase in agreement with the data, but at the cost of the agreement with the hadronic yields. In order that all the data on hadronic ratios, radial flow, and differential elliptic flow be reproduced, the sQGP must expand with a minimal viscosity, \\eta_Q, that is however even greater than the viscosity, \\eta_H, of its hadronic corona. However, because of the large entropy density difference of the two phases of QCD matter, the larger viscosity in the sQGP phase leads to nearly perfect fluid flow while the smaller entropy density of the hadronic corona strongly hinders the applicability of Euler hydrodynamics. The ``perfect fluid'' property of the sQGP is thus not due to a sudden reduction of the viscosity at the critical temperature Tc, but to a sudden increase of the entropy density of QCD matter and is therefore an important signature of deconfinement.
Quark–gluon plasma as the possible source of cosmological dark radiation
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Birrell, Jeremiah; Rafelski, Johann
2015-02-01T23:59:59.000Z
The effective number of neutrinos, NeffNeff, obtained from CMB fluctuations accounts for all effectively massless degrees of freedom present in the Universe, including but not limited to the three known neutrinos. Using a lattice-QCD derived QGP equation of state, we constrain the observed range of NeffNeff in terms of the freeze-out of unknown degrees of freedom near to quark–gluon hadronization. We explore limits on the coupling of these particles, applying methods of kinetic theory, and discuss the implications of a connection between NeffNeff and the QGP transformation for laboratory studies of QGP.
SYSTEMATIC STUDIES OF HEAVY ION COLLISIONS TO SEARCH FOR QUARK-GLUON PLASMA
Fuqiang Wang
2007-11-29T23:59:59.000Z
This is the final technical report for DOE Outstanding Junior Investigator (OJI) Award, 'Systematic Studies of Heavy Ion Collisions to Search for Quark-Gluon Plasma', grant DE-FG02-02ER41219, Principal Investigator (PI) Fuqiang Wang. The research under the grant was divided into two phases. The first concentrated on systematic studies of soft hadron production at low transverse momentum (p{sub T}), in particular the production of (anti-)baryon and strangeness in heavy ion collisions at RHIC energies. The second concentrated on measurements of di-hadron and multi-hadron jet-correlations and investigations of medium response to jets. The research was conducted at the Relativistic Heavy-Ion Collider (RHIC) at BNL with the Solenoidal Tracker At RHIC (STAR) experiment. The total grant is $214,000. The grant established a PC farm solely used for this research. The PC farm consists of 8 nodes with a total of 16 CPUs and 3 disk servers of total 2 TB shared storage. The current balance of the grant is $19,985. The positive balance is because an initial purchase of $22,600 for the PC farm came out of the PI's start-up fund due to the lateness of the award. The PC farm is an integral part of the Purdue Physics Department's computer cluster. The grant supported two Ph.D. graduate students. Levente Molnar was supported from July 2002 to December 2003, and worked on soft hadron production. His thesis title is Systematics of Identified Particle Production in pp, d-Au and Au-Au Collisions at RHIC Energies. He graduated in 2006 and now is a Postdoctoral fellow at INFN Sezione di Bari, Italy working on the ALICE experiment at the LHC. Jason Ulery was supported from January 2004 to July 2007. His thesis title is Two- and Three-Particle Jet-Like Correlations. He defended his thesis in October 2007 and is moving to Frankfurt University, Germany to work on the ALICE experiment at the LHC. The research by this grant resulted in 7 journal publications (2 PRL, 1 PLB, 1 PRC, 2 submitted and 1 in preparation), and 14 invited talks and 10 contributed talks at major conferences. These are listed at end of this report.
Quarks and gluons in hadrons and nuclei
Close, F.E. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA))
1989-12-01T23:59:59.000Z
These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. This lecture discusses the distribution functions of quarks and gluons in nucleons and nuclei, and how knowledge of these is necessary before some quark-gluon plasma searches can be analyzed. 56 refs., 2 figs.
Collisional processes of on-shell and off-shell heavy quarks in vacuum and in the Quark-Gluon-Plasma
H. Berrehrah; E. Bratkovskaya; W. Cassing; P. B. Gossiaux; J. Aichelin; M. Bleicher
2014-05-22T23:59:59.000Z
We study the heavy quark scattering on partons of the quark gluon plasma (QGP) being especially interested in the collisional (elastic) scattering processes of heavy quarks on quarks and gluons. We calculate the different cross sections for perturbative partons (massless on-shell particles in the vacuum) and for dynamical quasi-particles (off-shell particles in the QGP medium as described by the dynamical quasi-particles model "DQPM") using the leading order Born diagrams. Our results show clearly the effect of a finite parton mass and width on the perturbative elastic $(q(g) Q \\rightarrow q (g) Q)$ cross sections which depend on temperature $T$, energy density $\\epsilon$, the invariant energy $\\sqrt{s}$ and the scattering angle $\\theta$. Our detailed comparisons demonstrate that the finite width of the quasi-particles in the DQPM - which encodes the multiple partonic scattering - has little influence on the cross section for $q Q \\rightarrow q Q$ as well as $g Q \\rightarrow g Q$ scattering except close to thresholds. Thus when studying the dynamics of energetic heavy quarks in a QGP medium the spectral width of the degrees-of-freedom may be discarded. We have, furthermore, compared the cross sections from the DQPM with corresponding results from hard-thermal-loop (HTL) approaches. The HTL inspired models - essentially fixing the regulators by elementary vacuum cross sections and decay amplitudes instead of properties of the QGP at finite temperature - provide quite different results especially w.r.t. the temperature dependence of the $qQ$ and $gQ$ cross sections (in all settings). Accordingly, the transport properties of heavy quarks will be very different as a function of temperature when compared to DQPM results.
Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions
Yi Yin
2014-10-13T23:59:59.000Z
We extract the electrical conductivity $\\sigma_0$ of the quark gluon plasma(QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, $v_2$, based on the thermal photon spectrum at $0.4GeVproduction rate over the realistic hydrodynamic background and comparing the results with the preliminary data from the PHENIX Collaboration, we found that the electrical conductivity at QGP temperature is in the range: $0.4<\\sigma_0/(e^{2}T) <1.1$, which is comparable with recent studies on lattice. We also compare the contribution from the magnetic field and chiral anomaly to soft thermal photon $v_{2}$ with the data. We argue that at LHC, the chiral magnetic wave would give negative contribution to photon $v_2$.
Dynamical evolution of the chiral magnetic effect: applications to the quark-gluon plasma
Manuel, Cristina
2015-01-01T23:59:59.000Z
We study the dynamical evolution of the so-called chiral magnetic effect in an electromagnetic conductor. To this end, we consider the coupled set of corresponding Maxwell and chiral anomaly equations, and we prove that these can be derived from chiral kinetic theory. After integrating the chiral anomaly equation over space in a closed volume, it leads to a quantum conservation law of the total helicity of the system. A change in the magnetic helicity density comes together with a modification of the chiral fermion density. We study in Fourier space the coupled set of anomalous equations and we obtain the dynamical evolution of the magnetic fields, magnetic helicity density, and chiral fermion imbalance. Depending on the initial conditions we observe how the helicity might be transferred from the fermions to the magnetic fields, or vice versa, and find that the rate of this transfer also depends on the scale of wavelengths of the gauge fields in consideration. We then focus our attention on the quark-gluon pl...
Quark-Gluon Bags with Surface Tension
Kyrill Bugaev
2007-03-20T23:59:59.000Z
The temperature and chemical potential dependent surface tension of bags is introduced into the gas of quark-gluon bags model. This resolves a long standing problem of a unified description of the first and second order phase transition with the cross-over. Such an approach is necessary to model the complicated properties of quark-gluon plasma and hadronic matter from the first principles of statistical mechanics. The suggested model has an exact analytical solution and allows one to rigorously study the vicinity of the critical endpoint of the deconfinement phase transition. The existence of higher order phase transitions at the critical endpoint is discussed. In addition, we found that at the curve of a zero surface tension coefficient there must exist the surface induced phase tranition of the 2$^{nd}$ or higher order, which separates the pure quark gluon plasma (QGP) from the cross-over states, that are the mixed states of hadrons and QGP bags. Thus, the present model predicts that the critical endpoint of quantum chromodynamics is the tricritical endpoint.
Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Yin, Yi [University of Illinois, Physics Dept., IL (United States); Brookhaven National Laboratory, Physics Department, Upton, NY (United States)
2014-10-01T23:59:59.000Z
I extract the electrical conductivity ?0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v?, based on the thermal photon spectrum at 0.4GeV
plasma in hydrodynamic regime in the presence of magnetic field and chiral anomaly. By evolving the resulting soft thermal photon production rate over the realistic hydrodynamic background and comparing the results with the data from the PHENIX Collaboration, I found that the electrical conductivity at QGP temperature is in the range: 0.4
Chaotic dynamics in quark-gluon cascade
A. T. Temiraliev
2011-06-23T23:59:59.000Z
A map to the quark-gluon cascade on the basis of nonlinearity in the quark and gluon distributions in hadrons is proposed. Calculations of the quarks trajectories have shown the presence of the chaotic dynamics as a consequence of bifurcations.
Quark antiquark energies and the screening mass in a Quark-Gluon plasma at low and high temperatures
O. Kaczmarek; F. Zantow
2005-12-22T23:59:59.000Z
We discuss quark antiquark energies and the screening mass in hot QCD using the non-perturbative lattice approach. For this purpose we analyze properties of quark antiquark energies and entropies at infinitely large separation of the quark antiquark pair at low and high temperatures. In the limit of high temperatures these energies and entropies can be related perturbatively to the temperature dependence of the Debye mass and the coupling. On the one hand our analysis thus suggests that the quark antiquark energies at (infinite) large distances are rather related to the Debye screening mass and the coupling than to the temperature dependence of heavy-light meson masses. On the other hand we find no or only little differences in all mass scales introduced by us when changing from quenched to 2-flavor QCD at temperatures which are only moderately above the phase transition.
Photoemission rate of strongly interacting quark-gluon plasma at finite density
Jo, Kwanghyun; Sin, Sang-Jin [Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of)
2011-01-15T23:59:59.000Z
We calculate the thermal spectral function of strongly interacting Yang-Mills plasma with finite density using the holographic technique. The gravity dual of the finite temperature and density is taken as the Reissner-Nordstroem-anti-de Sitter black hole. In the presence of charge, linearized vector modes of gravitational and electromagnetic perturbation are coupled with each other. By introducing master variables for these modes, we solve the coupled system and calculate spectral function. The spectral function gets a new peak due to the density effect, which is most dramatic in the momentum plot with fixed frequency. We also calculate the photoemission rate of our gauge theory plasma from the spectral function for lightlike momentum. AC, dc conductivity, and their density dependence is also computed.
Chemical equilibration in viscous quark-gluon plasma and electromagnetic signals
A. K. Chaudhuri
1998-08-28T23:59:59.000Z
We investigate the chemical equilibration of the parton distributions in collisions of two heavy nuclei, assuming the partonic fluid to be ideal as well as viscous. The initial conditions are taken from HIJING calculations for Au+Au collisions at RHIC and LHC energies. It was seen that when the viscous drag is taken into account in the fluid flow, the life time of the plasma is increased by nearly a factor of 2. The temperature as well as fugacities evolve slowly than their ideal counterpart. The photon and lepton pair production was also investigated. There is a two fold increase in the photon and lepton pair numbers with viscosity on. The increase in the large $p_T$ photons and the large invariant mass lepton pairs are due to slower rate of temperature evolution.
Quark and Gluon Condensates in Isospin Matter
Lianyi He; Yin Jiang; Pengfei Zhuang
2009-05-03T23:59:59.000Z
Applying the Hellmann-Feynman theorem to a charged pion gas, the quark and gluon condensates at low isospin density are determined by precise pion properties. At intermediate density around $ f_\\pi^2m_\\pi$, from both the estimation for the dilute pion gas and the calculation with Nambu--Jona-Lasinio model, the quark condensate is strongly and monotonously suppressed, while the gluon condensate is enhanced and can be larger than its vacuum value. This unusual behavior of the gluon condensate is universal for Bose condensed matter of mesons. Our results can be tested by lattice calculations at finite isospin density.
Monte Carlo Simulation for Elastic Energy Loss of High-Energy Partons in Quark-Gluon Plasma
Jussi Auvinen; Kari J. Eskola; Hannu Holopainen; Thorsten Renk
2011-06-13T23:59:59.000Z
We examine the significance of $2 \\rightarrow 2$ partonic collisions as the suppression mechanism of high-energy partons in the strongly interacting medium formed in ultrarelativistic heavy ion collisions. For this purpose, we have developed a Monte Carlo simulation describing the interactions of perturbatively produced, non-eikonally propagating high-energy partons with the quarks and gluons from the expanding QCD medium. The partonic collision rates are computed in leading-order perturbative QCD (pQCD), while three different hydrodynamical scenarios are used to model the medium. We compare our results with the suppression observed in $\\sqrt{s_{NN}}=200$ GeV Au+Au collisions at the BNL-RHIC. We find the incoherent nature of elastic energy loss incompatible with the measured data and the effect of the initial state fluctuations small.
Akamatsu, Yukinao, E-mail: akamatsu@kmi.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Nagoya 464-8602 (Japan)] [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Nagoya 464-8602 (Japan); Inutsuka, Shu-ichiro [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)] [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Nonaka, Chiho [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Nagoya 464-8602 (Japan) [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Nagoya 464-8602 (Japan); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Takamoto, Makoto [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan) [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg (Germany)
2014-01-01T23:59:59.000Z
In this article, we present a state-of-the-art algorithm for solving the relativistic viscous hydrodynamics equation with the QCD equation of state. The numerical method is based on the second-order Godunov method and has less numerical dissipation, which is crucial in describing of quark–gluon plasma in high-energy heavy-ion collisions. We apply the algorithm to several numerical test problems such as sound wave propagation, shock tube and blast wave problems. In sound wave propagation, the intrinsic numerical viscosity is measured and its explicit expression is shown, which is the second-order of spatial resolution both in the presence and absence of physical viscosity. The expression of the numerical viscosity can be used to determine the maximum cell size in order to accurately measure the effect of physical viscosity in the numerical simulation.
Constituent gluons and the static quark potential
Greensite, Jeff
2015-01-01T23:59:59.000Z
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
Constituent gluons and the static quark potential
Jeff Greensite; Adam P. Szczepaniak
2015-05-19T23:59:59.000Z
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
The Role of Surface Tension for the Equation of State of Quark-Gluon Bags
K. A. Bugaev
2007-11-20T23:59:59.000Z
The temperature and chemical potential dependent surface tension of bags is introduced into the gas of quark-gluon bags model. The suggested model is solved analytically. It resolves a long standing problem of a unified description of the first and second order phase transition with the cross-over. Such an approach is necessary to model the complicated properties of quark-gluon plasma and hadronic matter from the first principles of statistical mechanics. In addition to the deconfinement phase transition, we found that at the curve of a zero surface tension coefficient there must exist the surface induced phase tranition of the 2-nd or higher order, which separates the pure quark gluon plasma (QGP) from the cross-over states. Thus, the present model predicts that the critical endpoint of quantum chromodynamics is the tricritical endpoint.
Hamza Berrehrah; Pol-Bernard Gossiaux; Jörg Aichelin; Wolfgang Cassing; Elena Bratkovskaya
2014-05-13T23:59:59.000Z
In this study we evaluate the dynamical collisional energy loss of heavy quarks, their interaction rate as well as the different transport coefficients (drag and diffusion coefficients, $\\hat{q}$, etc). We calculate these different quantities for i) perturbative partons (on-shell particles in the vacuum with fixed and running coupling) and ii) for dynamical quasi-particles (off-shell particles in the QGP medium at finite temperature $T$ with a running coupling in temperature as described by the dynamical quasi-particles model). We use the perturbative elastic $(q(g) Q \\rightarrow q (g) Q)$ cross section for the first case, and the Infrared Enhanced Hard Thermal Loop cross sections for the second. The results obtained in this work demonstrate the effects of a finite parton mass and width on the heavy quark transport properties and provide the basic ingredients for an explicit study of the microscopic dynamics of heavy flavors in the QGP - as formed in relativistic heavy-ion collisions - within transport approaches developed previously by the authors.
Gluon Radiation off Massive Quarks in a QCD Medium
N. Armesto; C. A. Salgado; U. A. Wiedemann
2004-05-19T23:59:59.000Z
Medium-induced gluon radiation from massless and massive quarks is treated in the same formalism. The dead cone which regulates gluon radiation from massive quarks in the vacuum at small angles, is filled in the medium but constitutes a small fraction of the available phase space. Our study indicates that the energy loss for charmed hadrons at RHIC should be smaller than for light hadrons, but still sizable.
First Measurement of the Fraction of Top Quark Pair Production Through Gluon-Gluon Fusion
CDF Collaboration; T. Aaltonen
2008-04-08T23:59:59.000Z
We present the first measurement of the fraction of top quark pair production through gluon-gluon fusion. We use 0.96/fb of s**(1/2)=1.96 TeV p-pbar collision data recorded with the CDF II detector at Fermilab. We identify the candidate t-tbar events with a high-energy charged lepton, a neutrino candidate, and four or more jets. Using charged particles with low transverse momentum in t-tbar events, we find the fraction of top quark pair production through gluon-gluon fusion to be 0.07+/-0.14(stat)+/-0.07(syst), corresponding to a 95% confidence level upper limit of 0.33, in agreement with the standard model NLO prediction of 0.15+/-0.05.
Quarks and gluons in hadrons and nuclei
Close, F.E. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA))
1989-01-01T23:59:59.000Z
These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. 38 refs.
Hard Thermal Loops, Weak Gravitational Fields and The Quark Gluon Energy Momentum Tensor
E. A. Gaffney
1994-09-13T23:59:59.000Z
We use an auxiliary field construction to discuss the hard thermal loop effective action associated with massless thermal SU(N) QCD interacting with a weak gravitational field. It is demonstrated that the previous attempt to derive this effective action has only been partially successful and that it is presently only known to first order in the graviton coupling constant. This is still sufficient to enable a calculation of a symmetric traceless quark gluon plasma energy momentum tensor. Finally, we comment on the conserved currents and charges of the derived energy momentum tensor.
SOFT-GLUON DYNAMICS FOR HEAVY QUARK-ANTIQUARK SYSTEMS
Shizuya, Ken-ichi
2013-01-01T23:59:59.000Z
gluons Ak, system, the binding energy bE and soft gluons inbe SOFT-GLUON DYNAMICS FOR HEAVY QUAR_K-ANTIQUARK SYSTEMS s·soft external perturbations (via gluons sof·ter than the system
Color Glass Condensates in dense quark matter and quantum Hall states of gluons
Aiichi Iwazaki
2006-04-26T23:59:59.000Z
We apply the effective theory of color glass condensate to the analysis of gluon states in dense quark matter, in which the saturation region of gluons is also present. We find that in the region two point function of gluons shows algebraic long range order. The order is completely the same as the one gluons show in the dense quark matter, which form quantum Hall states. The order leads to the vanishing of massless gluon pole. We also find that the saturation region of gluons extends from small $x$ to even large $x\\lesssim 1$ in much dense quark matter. We point out a universality that the color glass condensate is a property of hadrons at high energy and of quark matter at high baryon density.
Shear viscosity of a nonperturbative gluon plasma
Dmitri Antonov
2012-02-10T23:59:59.000Z
Shear viscosity is evaluated within a model of the gluon plasma, which is based entirely on the stochastic nonperturbative fields. We consider two types of excitations of such fields, which are characterized by the thermal correlation lengths ~ 1/(g^2 T) and ~ 1/(g^4 T), where "g" is the finite-temperature Yang-Mills coupling. Excitations of the first type correspond to the genuine nonperturbative stochastic Yang-Mills fields, while excitations of the second type mimic the known result for the shear viscosity of the perturbative Yang-Mills plasma. We show that the excitations of the first type produce only an O(g^{10})-correction to this result. Furthermore, a possible interference between excitations of these two types yields a somewhat larger, O(g^7), correction to the leading perturbative Yang-Mills result. Our analysis is based on the Fourier transformed Euclidean Kubo formula, which represents an integral equation for the shear spectral density. This equation is solved by seeking the spectral density in the form of the Lorentzian Ans\\"atze, whose widths are defined by the two thermal correlation lengths and by their mean value, which corresponds to the said interference between the two types of excitations. Thus, within one and the same formalism, we reproduce the known result for the shear viscosity of the perturbative Yang-Mills plasma, and account for possible nonperturbative corrections to it.
Gluon Radiation in Top Quark Production and Decay at $e^+e^-$ Colliders
Cosmin Macesanu; Lynne H. Orr
2000-12-18T23:59:59.000Z
We study gluon radiation in top quark production above threshold at high energy $e^+e^-$ colliders. We allow for the top quarks to be off-shell, considering radiation in both the top production and decay processes simultaneously. Our calculation includes all top width effects, spin correlations, and $b$ quark mass effects. We study the effects of gluon radiation on top mass reconstuction and examine the interference between production- and decay-stage radiation, which can be sensitive to the value of the top quark decay width.
QCD plasma parameters and the gauge-dependent gluon propagator
Kobes, R.; Kunstatter, G.; Rebhan, A. (Department of Physics, University of Winnipeg, 515 Portage Avenue, Winnipeg, Manitoba (Canada) Institut fuer Theoretische Physik, Technische Universitaet Wien, Wiedner Haupstrasse 8-10, A-1040 Vienna (Austria))
1990-06-18T23:59:59.000Z
We derive the Ward identities that determine the gauge dependence of the QCD dispersion relations obtained from the ordinary gluon propagator in a certain class of gauges. These identities hold for complex structure functions at both zero and finite temperature. A direct consequence of our analysis is that the gauge dependence of the gluon-plasma damping constant obtained in recent one-loop calculations is due to an inconsistent approximation scheme.
Lower scaling dimensions of quarks and gluons and new energy scales
F. Palumbo
1996-05-08T23:59:59.000Z
We consider the possibility that quarks and gluons, due to confinement, have lower scaling dimensions. In such a case there appear naturally new energy scales below which the standard theory is recovered. Arguments are given whereby for dimension $1/2$ of the quarks the theory is unitary also above these energy scales.
Magnetic component of gluon plasma and its viscosity
M. N. Chernodub; H. Verschelde; V. I. Zakharov
2009-05-15T23:59:59.000Z
We discuss the role of the magnetic degrees of freedom of the gluon plasma in its viscosity. The main assumption is that motions of the magnetic component and of the rest of the plasma can be considered as independent. The magnetic component in the deconfined phase is described by a three-dimensional (Euclidean) field theory. The parameters of the theory can be estimated phenomenologically, from the lattice data. It is not ruled out that the magnetic component is superfluid.
Differential Higgs+jet production in bottom quark annihilation and gluon fusion
Marius Wiesemann
2012-11-05T23:59:59.000Z
We present recent developments concerning Higgs production in bottom quark annihilation and gluon fusion. For bottom quark annihilation, we show the transverse momentum distribution of the associated jets. Furthermore, we discuss the distribution of events into n-jet bins for n=0 and n>0 at NNLO and NLO, respectively. For gluon fusion, the quality of the heavy-top limit for differential quantities at O(\\alpha_s^4) is studied by taking into account higher order terms in the 1/m_{top} expansion.
Quark Potential in a Quark-Meson Plasma
Chengfu Mu; Pengfei Zhuang
2008-03-05T23:59:59.000Z
We investigate quark potential by considering meson exchanges in the two flavor Nambu--Jona-Lasinio model at finite temperature and density. There are two kinds of oscillations in the chiral restoration phase, one is the Friedel oscillation due to the sharp quark Fermi surface at high density, and the other is the Yukawa oscillation driven by the complex meson poles at high temperature. The quark-meson plasma is strongly coupled in the temperature region $1\\le T/T_c \\lesssim 3$ with $T_c$ being the critical temperature of chiral phase transition. The maximum coupling in this region is located at the critical point.
Production of $K^{0}_{S}$ and $\\Lambda$ in Quark and Gluon Jets from $Z^{0}$ Decay
Ackerstaff, K; Allison, J; Altekamp, N; Anderson, K J; Anderson, S; Arcelli, S; Asai, S; Ashby, S F; Axen, D A; Azuelos, Georges; Ball, A H; Barberio, E; Barlow, R J; Bartoldus, R; Batley, J Richard; Baumann, S; Bechtluft, J; Behnke, T; Bell, K W; Bella, G; Bentvelsen, Stanislaus Cornelius Maria; Bethke, Siegfried; Betts, S; Biebel, O; Biguzzi, A; Bird, S D; Blobel, Volker; Bloodworth, Ian J; Bobinski, M; Bock, P; Böhme, J; Boutemeur, M; Braibant, S; Bright-Thomas, P G; Brown, R M; Burckhart, Helfried J; Burgard, C; Bürgin, R; Capiluppi, P; Carnegie, R K; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Chrisman, D; Ciocca, C; Clarke, P E L; Clay, E; Cohen, I; Conboy, J E; Cooke, O C; Couyoumtzelis, C; Coxe, R L; Cuffiani, M; Dado, S; Dallavalle, G M; Davis, R; De Jong, S; del Pozo, L A; de Roeck, A; Desch, Klaus; Dienes, B; Dixit, M S; Doucet, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Eatough, D; Estabrooks, P G; Evans, H G; Fabbri, Franco Luigi; Fanfani, A; Fanti, M; Faust, A A; Fiedler, F; Fierro, M; Fischer, H M; Fleck, I; Folman, R; Fürtjes, A; Futyan, D I; Gagnon, P; Gary, J W; Gascon, J; Gascon-Shotkin, S M; Geich-Gimbel, C; Geralis, T; Giacomelli, G; Giacomelli, P; Gibson, V; Gibson, W R; Gingrich, D M; Glenzinski, D A; Goldberg, J; Gorn, W; Grandi, C; Gross, E; Grunhaus, Jacob; Gruwé, M; Hanson, G G; Hansroul, M; Hapke, M; Hargrove, C K; Hartmann, C; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Herndon, M; Herten, G; Heuer, R D; Hildreth, M D; Hill, J C; Hillier, S J; Hobson, P R; Höcker, Andreas; Homer, R James; Honma, A K; Horváth, D; Hossain, K R; Howard, R; Hüntemeyer, P; Igo-Kemenes, P; Imrie, D C; Ishii, K; Jacob, F R; Jawahery, A; Jeremie, H; Jimack, Martin Paul; Joly, A; Jones, C R; Jovanovic, P; Junk, T R; Karlen, D A; Kartvelishvili, V G; Kawagoe, K; Kawamoto, T; Kayal, P I; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Koetke, D S; Kokott, T P; Kolrep, M; Komamiya, S; Kowalewski, R V; Kress, T; Krieger, P; Von Krogh, J; Kyberd, P; Lafferty, G D; Lanske, D; Lauber, J; Lautenschlager, S R; Lawson, I; Layter, J G; Lazic, D; Lee, A M; Lefebvre, E; Lellouch, Daniel; Letts, J; Levinson, L; Liebisch, R; List, B; Littlewood, C; Lloyd, A W; Lloyd, S L; Loebinger, F K; Long, G D; Losty, Michael J; Ludwig, J; Liu, D; Macchiolo, A; MacPherson, A L; Mannelli, M; Marcellini, S; Markopoulos, C; Martin, A J; Martin, J P; Martínez, G; Mashimo, T; Mättig, P; McDonald, W J; McKenna, J A; McKigney, E A; McMahon, T J; McPherson, R A; Meijers, F; Menke, S; Merritt, F S; Mes, H; Meyer, J; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Mir, R; Mohr, W; Montanari, A; Mori, T; Nagai, K; Nakamura, I; Neal, H A; Nellen, B; Nisius, R; O'Neale, S W; Oakham, F G; Odorici, F; Ögren, H O; Oreglia, M J; Orito, S; Pálinkás, J; Pásztor, G; Pater, J R; Patrick, G N; Patt, J; Pérez-Ochoa, R; Petzold, S; Pfeifenschneider, P; Pilcher, J E; Pinfold, James L; Plane, D E; Poffenberger, P R; Poli, B; Polok, J; Przybycien, M B; Rembser, C; Rick, Hartmut; Robertson, S; Robins, S A; Rodning, N L; Roney, J M; Roscoe, K; Rossi, A M; Rozen, Y; Runge, K; Runólfsson, O; Rust, D R; Sachs, K; Saeki, T; Sahr, O; Sang, W M; Sarkisyan-Grinbaum, E; Sbarra, C; Schaile, A D; Schaile, O; Scharf, F; Scharff-Hansen, P; Schieck, J; Schmitt, B; Schmitt, S; Schöning, A; Schörner-Sadenius, T; Schröder, M; Schumacher, M; Schwick, C; Scott, W G; Seuster, R; Shears, T G; Shen, B C; Shepherd-Themistocleous, C H; Sherwood, P; Siroli, G P; Sittler, A; Skuja, A; Smith, A M; Snow, G A; Sobie, Randall J; Söldner-Rembold, S; Sproston, M; Stahl, A; Stephens, K; Steuerer, J; Stoll, K; Strom, D; Ströhmer, R; Tafirout, R; Talbot, S D; Tanaka, S; Taras, P; Tarem, S; Teuscher, R; Thiergen, M; Thomson, M A; Von Törne, E; Torrence, E; Towers, S; Trigger, I; Trócsányi, Z L; Tsur, E; Turcot, A S; Turner-Watson, M F; Van Kooten, R; Vannerem, P; Verzocchi, M; Vikas, P; Voss, H; Wäckerle, F; Wagner, A; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wermes, N; White, J S; Wilson, G W; Wilson, J A; Wyatt, T R; Yamashita, S; Yekutieli, G; Zacek, V; Zer-Zion, D
1999-01-01T23:59:59.000Z
The production of K^0_S mesons and Lambda baryons in quark and gluon jets has been investigated using two complementary techniques. In the first approach, which provides high statistical accuracy, jets were selected using different jet finding algorithms and ordered according to their energy. Production rates were determined taking into account the dependences of quark and gluon compositions as a function of jet energy as predicted by Monte Carlo models. Selecting three-jet events with the k_perp (Durham) jet finder (y_cut = 0.005), the ratios of K^0_S and Lambda production rates in gluon and quark jets relative to the mean charged particle multiplicity were found to be 1.10 +/- 0.02 +/- 0.02 and 1.41 +/- 0.04 +/- 0.04, respectively, where the first uncertainty is statistical and the second is systematic. In the second approach, a new method of identifying quark jets based on the collimation of energy flow around the jet axis is introduced and was used to anti-tag gluon jets in symmetric (Y-shaped) three-jet ...
The EMC effect: local nuclear dynamics or quark-gluon dynamics?
Canal, Carlos A García; Vento, Vicente
2012-01-01T23:59:59.000Z
It has been recently confirmed that the magnitude of the EMC effect measured in electron deep inelastic scattering is linearly related to the Short Range Correlation scaling factor obtained from electron inclusive scattering. By using an effective nucleon mass approach we are able to understand the interplay between the quark-gluon and hadronic degrees of freedom in the discussion of the EMC effect.
A possible evidence of the hadron-quark-gluon mixed phase formation in nuclear collisions
Kizka, V A; Bugaev, K A; Oliinychenko, D R
2015-01-01T23:59:59.000Z
The performed systematic meta-analysis of the quality of data description (QDD) of existing event generators of nucleus-nucleus collisions allows us to extract a very important physical information. Our meta-analysis is dealing with the results of 10 event generators which describe data measured in the range of center of mass collision energies from 3.1 GeV to 17.3 GeV. It considers the mean deviation squared per number of experimental points obtained by these event generators, i.e. the QDD, as the results of independent meta-measurements. These generators and their QDDs are divided in two groups. The first group includes the generators which account for the quark-gluon plasma formation during nuclear collisions (QGP models), while the second group includes the generators which do not assume the QGP formation in such collisions (hadron gas models). Comparing the QDD of more than a hundred of different data sets of strange hadrons by two groups of models, we found two regions of the equal quality description o...
Shape Studies of Quark Jets versus Gluon Jets at sqrt(s) = 10 GeV
Baringer, Philip S.
1992-12-01T23:59:59.000Z
, Kansas 66045 'University ofMinnesota, Minneapolis, Minnesota 55455 (Received 1 June 1992) Using date from e e annihilation into hadrons taken on the Y(1S) and continuum, we are able to compare event properties of three-gluon (ggg) and quark-antiquark (qq...(1S). Contrary to the notion that two-gluon (gg) events are globally very similar to qq jets, we infer from a study of the yb (J=0 or 2) states that gg event shapes more closely resemble ggg decays of the Y(1S),whereas qqg decays of the yb (J= 1...
Photon production from gluon mediated quark-anti-quark annihilation at confinement
Sarah Campbell
2015-04-07T23:59:59.000Z
Heavy ion collisions at RHIC produce direct photons at low transverse momentum, $p_{T}$ from 1-3 GeV/c, in excess of the $p$$+$$p$ spectra scaled by the nuclear overlap factor, $T_{AA}$. These low $p_{T}$ photons have a large azimuthal anisotropy, $v_{2}$. Theoretical models, including hydrodynamic models, struggle to quantitatively reproduce the large low $p_{T}$ direct photon excess and $v_{2}$ in a self-consistent manner. This paper presents a description of the low $p_{T}$ photon flow as the result of increased photon production from soft-gluon mediated $q$-$\\bar{q}$ interactions as the system becomes color-neutral. This production mechanism will generate photons that follow constituent quark number, $n_{q}$, scaling of $v_{2}$ with an $n_{q}$ value of two for direct photons. $\\chi^{2}$ comparisons of the published PHENIX direct photon and identified particle $v_{2}$ measurements finds that $n_{q}$-scaling applied to the direct photon $v_{2}$ data prefers the value $n_{q}=1.8$ and agrees with $n_{q}=2$ within errors in most cases. The 0-20\\% and 20-40\\% Au$+$Au direct photon data are compared to a coalescence-like Monte Carlo simulation that calculates the direct photon $v_{2}$ while describing the shape of the direct photon $p_{T}$ spectra in a consistent manner. The simulation, while systematically low, is in agreement with the Au$+$Au measurement at $p_{T}<3$ GeV/c in both centrality bins. Furthermore, this model predicts that higher order flow harmonics, $v_{n}$, in direct photons will follow the $n_{q}$-scaling laws seen in identified hadron $v_{n}$ with an $n_{q}$ value of approximately two.
Properties of the SU(Nc) Gluon Plasma
Saumen Datta; Sourendu Gupta
2009-10-15T23:59:59.000Z
We investigate the deconfinement transition in SU(Nc) gauge theories, and properties of the deconfined phase. A detailed lattice study of SU(4) and SU(6) gauge theories are conducted, and finite volume and cutoff effects on thermodynamic observables are studied. The scaling of the deconfinement transition point with lattice spacing is used to calculate the scale, Lambda_MSbar. The continuum estimates of the thermodynamic quantities are used to study properties of the gluon plasma. In particular, the approach to conformal limit is studied. We do not find any evidence of a strongly coupled, conformal phase in these theories.
Bulk viscosity in a plasma of confining gluons
Wojciech Florkowski; Radoslaw Ryblewski; Nan Su; Konrad Tywoniuk
2015-04-13T23:59:59.000Z
We investigate dynamic properties of a plasma whose constituents are confining gluons resulting from the Gribov quantization. In a static formulation, this system reproduces qualitatively the pure-glue equation of state and thereby encodes crucial features of the phase transition. The dynamic description proposed in this work allows us to study non-equilibrium transport phenomena with the inclusion of confinement effects. In particular, we determine the non-equilibrium behaviour of the interaction measure (trace anomaly) and find the form of the bulk viscosity coefficient. The latter may be used in phenomenological applications to heavy-ion collisions.
Bulk viscosity in a plasma of confining gluons
Florkowski, Wojciech; Su, Nan; Tywoniuk, Konrad
2015-01-01T23:59:59.000Z
We investigate dynamic properties of a plasma whose constituents are confining gluons resulting from the Gribov quantization. In a static formulation, this system reproduces qualitatively the pure-glue equation of state and thereby encodes crucial features of the phase transition. The dynamic description proposed in this work allows us to study non-equilibrium transport phenomena with the inclusion of confinement effects. In particular, we determine the non-equilibrium behaviour of the interaction measure (trace anomaly) and find the form of the bulk viscosity coefficient. The latter may be used in phenomenological applications to heavy-ion collisions.
Production of two Z-bosons in gluon fusion in the heavy top quark approximation
Melnikov, Kirill
2015-01-01T23:59:59.000Z
We compute QCD radiative corrections to the continuum production of a pair of Z-bosons in the annihilation of two gluons. We only consider the contribution of the top quark loops and we treat them assuming that $m_t$ is much larger than any other kinematic invariant in the problem. We estimate the QCD corrections to $pp \\to ZZ$ using the first non-trivial term in the expansion in the inverse top quark mass and we compare them to QCD corrections of the signal process, $pp \\to H \\to ZZ$.
atmospheric thermal plasmas: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
by plasma instabilities in the thermalization of quark-gluon plasmas at very high energy. Conference talk presented at Strong and Electroweak Mattter 2004, Helsinki, Finland,...
Gluon Radiation off Hard Quarks in a Nuclear Environment: Opacity Expansion
Urs Achim Wiedemann
2000-08-15T23:59:59.000Z
We study the relation between the Baier-Dokshitzer-Mueller-Peigne-Schiff (BDMPS) and Zakharov formalisms for medium-induced gluon radiation off hard quarks, and the radiation off very few scattering centers. Based on the non-abelian Furry approximation for the motion of hard partons in a spatially extended colour field, we derive a compact diagrammatic and explicitly colour trivial expression for the N-th order term of the kt-differential gluon radiation cross section in an expansion in the opacity of the medium. Resumming this quantity to all orders in opacity, we obtain Zakharov's path-integral expression (supplemented with a regularization prescription). This provides a new proof of the equivalence of the BDMPS and Zakharov formalisms which extends previous arguments to the kt-differential cross section. We give explicit analytical results up to third order in opacity for both the gluon radiation cross section of free incoming and of in-medium produced quarks. The N-th order term in the opacity expansion of the radiation cross section is found to be a convolution of the radiation associated to N-fold rescattering and a readjustment of the probabilities that rescattering occurs with less than N scattering centers. Both informations can be disentangled by factorizing out of the radiation cross section a term which depends only on the mean free path of the projectile. This allows to infer analytical expressions for the totally coherent and totally incoherent limits of the radiation cross section to arbitrary orders in opacity.
Martí i García, S
1995-01-01T23:59:59.000Z
Three jet events arising from decays of the Z^0 boson, collected by the DELPHI detector at LEP, were used to measure differences in the properties of quark and gluon jet fragmentation. Gluon jets were anti-tagged in b\\bar{b}g events, by identifiying b quark jets with high purities. Unbiased quark jets came from events q\\bar{q}\\gamma with two jets plus one photon. A comparison of quark and gluon jet properties in different energy ranges was performed for the first time and within the same detector. The average value of the ratio of the mean charged multiplicities of gluon and quark jets was measured to be \\[ 1.232 \\pm 0.026 (\\mbox{esta.}) \\pm 0.018 (\\mbox{sist.}) \\] where the fraction of b-quark initiates jets was 11\\% and the Durham jet finding algorithm has been used for the selection of three jet events. In agreement with QCD an increase of this ratio with energy was observed at a 3\\sigma level. A further dependence of this ratio related with the angular acceptance of the algorithm used to reconstruct jets ...
Gluons and the Quark Sea at High Energies: Distributions, Polarization, Tomography
Boer, Daniel; /Groningen U.; Diehl, Markus; /DESY; Milner, Richard; /MIT; Venugopalan, Raju; /Brookhaven; Vogelsang, Werner; /Tubingen U.; Kaplan, David; /Washington U., Seattle; Montgomery, Hugh; /Jefferson Lab; Vigdor, Steven; /Brookhaven; Accardi, A.; /Jefferson Lab; Aschenauer, E.C.; /Brookhaven; Burkardt, M.; /New Mexico State U.; Ent, R.; /Jefferson Lab; Guzey, V.; /Jefferson Lab; Hasch, D.; /Frascati; Kumar, K.; /Massachusetts U., Amherst; Lamont, M.A.C.; /Brookhaven; Li, Ying-chuan; /Brookhaven; Marciano, W.; /Brookhaven; Marquet, C.; /CERN; Sabatie, F.; /IRFU, SPhN, Saclay; Stratmann, M.; /Brookhaven /LBL, Berkeley /Buenos Aires U. /Antwerp U. /Pelotas U. /Moncton U. /Santa Maria U., Valparaiso /CCTVal, Valparaiso /Hefei, CUST /Shandong U., Weihai /Boskovic Inst., Zagreb /Zagreb U., Phys. Dept. /Jyvaskyla U. /Orsay, LPT /Paris U., VI-VII /Ecole Polytechnique, CPHT /IRFU, SPhN, Saclay /Saclay, SPhT /Ruhr U., Bochum /Giessen U. /DESY /Hamburg U., Inst. Theor. Phys. II /Heidelberg U. /Mainz U., Inst. Kernphys. /Mainz U., Inst. Phys. /Regensburg U. /Tubingen U. /Wuppertal U. /DESY /Cagliari U. /INFN, Cagliari /Frascati /Milan U. /INFN, Milan /INFN, Pavia /Pavia U. /INFN, Perugia /Perugia U.; /more authors..
2012-06-07T23:59:59.000Z
This report on the science case for an Electron-Ion Collider (EIC) is the result of a ten-week program at the Institute for Nuclear Theory (INT) in Seattle (from September 13-November 19, 2010), motivated by the need to develop a strong case for the continued study of the QCD description of hadron structure in the coming decades. Hadron structure in the valence quark region will be studied extensively with the Jefferson Lab 12 GeV science program, the subject of an INT program the previous year. The focus of the INT program was on understanding the role of gluons and sea quarks, the important dynamical degrees of freedom describing hadron structure at high energies. Experimentally, the most direct and precise way to access the dynamical structure of hadrons and nuclei at high energies is with a high luminosity lepton probe in collider mode. An EIC with optimized detectors offers enormous potential as the next generation accelerator to address many of the most important, open questions about the fundamental structure of matter. The goal of the INT program, as captured in the writeups in this report, was to articulate these questions and to identify golden experiments that have the greatest potential to provide definitive answers to these questions. At resolution scales where quarks and gluons become manifest as degrees of freedom, the structure of the nucleon and of nuclei is intimately connected with unique features of QCD dynamics, such as confinement and the self-coupling of gluons. Information on hadron sub-structure in DIS is obtained in the form of 'snapshots' by the 'lepton microscope' of the dynamical many-body hadron system, over different momentum resolutions and energy scales. These femtoscopic snapshots, at the simplest level, provide distribution functions which are extracted over the largest accessible kinematic range to assemble fundamental dynamical insight into hadron and nuclear sub-structure. For the proton, the EIC would be the brightest femtoscope scale lepton-collider ever, exceeding the intensity of the HERA collider a thousand fold. HERA, with its center-of-mass (CM) energy of 320 GeV, was built to search for quark substructure. An EIC, with its scientific focus on studying QCD in the regime where the sea quarks and gluons dominate, would have a lower CM energy. In a staged EIC design, the CM energy will range from 50-70 GeV in stage I to approximately twice that for the full design. In addition to being the first lepton collider exploring the structure of polarized protons, an EIC will also be the first electron-nucleus collider, probing the gluon and sea quark structure of nuclei for the first time. Following the same structure as the scientific discussions at the INT, this report is organized around the following four major themes: (1) The spin and flavor structure of the proton; (2) Three dimensional structure of nucleons and nuclei in momentum and configuration space; (3) QCD matter in nuclei; and (4) Electroweak physics and the search for physics beyond the Standard Model. In this executive summary, we will briefly outline the outstanding physics questions in these areas and the suite of measurements that are available with an EIC to address these. The status of accelerator and detector designs is addressed at the end of the summary. Tables of golden measurements for each of the key science areas outlined are presented on page 12. In addition, each chapter in the report contains a comprehensive overview of the science topic addressed. Interested readers are encouraged to read these and the individual contributions for more details on the present status of EIC science.
Gluon condensates and c, b quark masses from quarkonia ratios of moments
Stephan Narison
2011-10-13T23:59:59.000Z
We extract (for the first time) the ratio of the gluon condensate / expressed in terms of the liquid instanton radius rho_c from charmonium moments sum rules by examining the effects of in the determinations of both rho_c and the running MS mass m_c(m_c). Using a global analysis of selected ratios of moments at different Q^2=0, 4m_c^2 and 8m_c^2 and taking from 0.06 GeV^4, where the estimate of rho_c is almost independent of , we deduce: rho_c=0.98(21) GeV^{-1} which corresponds to = (31+- 13) GeV^2 . The value of m_c(m_c) is less affected (within the errors) by the variation of , where a common solution from different moments are reached for greater than 0.02 GeV^4. Using the values of =0.06(2) GeV^4 from some other channels and the previous value of , we deduce: m_c(m_c)=1260(18) MeV and m_b(m_b)=4173(10) MeV, where an estimate of the 4-loops contribution has been included. Our analysis indicates that the errors in the determinations of the charm quark mass without taking into account the ones of the gluon condensates have been underestimated. To that accuracy, one can deduce the running light and heavy quark masses and their ratios evaluated at M_Z, where it is remarkable to notice the approximate equalities: m_s/m_u= m_b/m_s= m_t/m_b= 51(4), which might reveal some eventual underlying novel symmetry of the quark mass matrix in some Grand Unified Theories.
H. Malekzadeh
2008-10-29T23:59:59.000Z
Enforcing color and electric charge neutrality conditions on the three-flavor color superconducting matter, I derive the explicit form of the quark propagators and the gluon self-energies for the gapless and the ordinary color-flavor-locked phases.
Correlations of Abelian monopoles in quark-gluon plasma
V. V. Braguta; A. Yu. Kotov
2012-08-27T23:59:59.000Z
In this paper the properties of thermal Abelian monopoles in the deconfinement phase of the SU(2) gluodynamics are considered. In particular, to study the properties of the Abelian monopole component of QGP we calculate three-point correlation functions of monopoles for different temperatures from the region $T/T_c \\in (1.5, 6.8)$. The results of the calculation show that the three-point correlation functions can be described by independent pair correlations of monopoles. From this one can conclude that the system of Abelian monopoles in QGP reveals the properties of a dilute gas. In addition, one can assert that the interaction between Abelian monopoles is a pair interaction and there are no three-particle forces acting between monopoles.
Charmonium properties in the quark-gluon plasma
M. B. Oktay; M. J. Peardon; J. I. Skullerud; G. Aarts; C. R. Allton
2007-10-15T23:59:59.000Z
We present results for charmonium correlators and spectral functions in 2-flavour CD on anisotropic lattices. Our results indicate that the S-waves (J/psi and eta_c) survive up to temperatures close to 2T_c, while the P-waves (chi_c0 and chi_c1) melt away below 1.2T_c.
EXPLORING THE QUARK GLUON PLASMA WITH BIKASH SINHA.
MCLERRAN, L.
2005-02-01T23:59:59.000Z
This paper presents a personal account of the scientific and professional adventures of Bikash Sinha on the occasion of the celebration of his 60th birthday held in Calcutta on Feb 7, 2005.
Baryon number fluctuation and the quark-gluon plasma
Lin, ZW; Ko, Che Ming.
2001-01-01T23:59:59.000Z
#, modification of high pT particle spec- trum @4#, and M T scaling @5# and double phi peaks @6# in the dilepton spectrum. Recently, event-by-event fluctuations of various particles have also attracted much attention @7#. Since the baryon and charge numbers... of Ref. @12# for the production of particles with con- serving charges, we have the following master equation for the multiplicity distribution of BB? pairs: dPn dt 5 G V ^Nm1&^Nm2&~Pn212Pn! 2 L V @n 2Pn2~n11 !2Pn11# . ~1! In the above, Pn(t...
Probing the Quark Sea and Gluons: the Electron-Ion Collider Projects
Rolf Ent
2012-04-01T23:59:59.000Z
EIC is the generic name for the nuclear science-driven Electron-Ion Collider presently considered in the US. Such an EIC would be the world’s first polarized electron-proton collider, and the world’s first e-A collider. Very little remains known about the dynamical basis of the structure of hadrons and nuclei in terms of the fundamental quarks and gluons of Quantum Chromodynamics (QCD). A large community effort to sharpen a compelling nuclear science case for an EIC occurred during a ten-week program taking place at the Institute for Nuclear Theory (INT) in Seattle from September 13 to November 19, 2010. The critical capabilities of a stage-I EIC are a range in center-of-mass energies from 20 to 70 GeV and variable, full polarization of electrons and light ions (the latter both longitudinal and transverse), ion species up to A=200 or so, multiple interaction regions, and a high luminosity of about 10{sup 34} electron-nucleons per cm{sup 2} and per second. The physics program of such a stage-I EIC encompass inclusive measurements (ep/A{yields}e'+X), which require detection of the scattered lepon and/or the full scattered hadronic debris with high precision, semi-inclusive processes (ep/A{yields}e'+h+X), which require detection in coincidence with the scattered lepton of at least one (current or target region) hadron; and exclusive processes (ep/A{yields}e'+N'/A'+{gamma}/m), which require detection of all particles in the reaction. The main science themes of an EIC are to i) map the spin and spatial structure of quarks and gluons in nucleons, ii) discover the collective effects of gluons in atomic nuclei, and (iii) understand the emergence of hadronic matter from color charge. In addition, there are opportunities at an EIC for fundamental symmetry and nucleon structure measurements using the electroweak probe. To truly make headway to image the sea quarks and gluons in nucleons and nuclei, the EIC needs high luminosity over a range of energies as more exclusive scattering probabilities are small, and any integrated detector/interaction region design needs to provide uniform coverage to detect spectator and diffractive products. This is because e-p and even more e-A colliders have a large fraction of their science related to what happens to the nucleon or ion beams. As a result, the philosophy of integration of complex detectors into an extended interaction region faces challenging constraints. Designs feature crossing angles between the protons or heavy ions during collisions with electrons, to remove potential problems for the detector induced by synchrotron radiation. Designs allocate quite some detector space before the final-focus ion quads, at the cost of luminosity, given that uniform detection coverage is a must for deep exclusive and diffractive processes. The integrated EIC detector/interaction region design at JLab focused on establishing full acceptance for such processes over a wide range of proton energies (20-100 GeV) with well achievable interaction region magnets. The detector design at BNL uses the higher ion beam energies to achieve good detection efficiency for instance for protons following a DVCS reaction, for proton beam energies starting from 100 GeV. Following a recommendation of the 2007 US Nuclear Science Long-Range Planning effort, the DOE Office of Nuclear Physics (DOE/NP) has allocated accelerator R&D funds to lay the foundation for a polarized EIC. BNL, in association with JLab and DOE/NP, has also established a generic detector R&D program to address the scientific requirements for measurements at a future EIC.
Mixed heavy-quark-gluon condensate in the stochastic vacuum model and dual superconductor
Dmitri Antonov
2005-09-30T23:59:59.000Z
The world-line formalism is used for the evaluation of the mixed heavy-quark-gluon condensate in two models of QCD - the stochastic vacuum model and the dual superconductor one. Calculations are performed for an arbitrary dimensionality of space-time $d\\ge 2$. While in the stochastic vacuum model, the condensate is UV finite up to $d=8$, in the dual superconductor model it is UV divergent at any $d\\ge 2$. A regularization of this divergence is proposed, which makes quantitative the condition of the type-II dual superconductor. The obtained results are generalized to the case of finite temperatures. Corrections to the both, mixed and standard, heavy-quark condensates, which appear due to the variation of the gauge field at the scale of the vacuum correlation length, are evaluated within the stochastic vacuum model. These corrections diminish the absolute values of the condensates, as well as the ratio of the mixed condensate to the standard one.
Akbari Jahan; D. K. Choudhury
2010-12-30T23:59:59.000Z
In recent years, Fractal Inspired Models of quark and gluon densities at small x have been proposed. In this paper, we investigate longitudinal structure function F-L (x, Q2) within this approach. We make predictions using the QCD based approximate relation between the longitudinal structure function and the gluon density. As the Altarelli-Martinelli equation for the longitudinal structure function cannot be applied to Model I due to the presence of a singularity in the Bjorken x-space we consider Model II only. The qualitative feature of the prediction of Model II is found to be compatible with the QCD expectation.
Malheiro, M.; Dey, M.; Delfino, A.; Dey, J. [Department of Physics, University of Maryland College Park, Maryland 20742-4111 (United States)] [Department of Physics, University of Maryland College Park, Maryland 20742-4111 (United States); [Instituto de Fisica, Universidade Federal Fluminense, 24210-340, Niteroi, Rio de Janeiro, Brasil; [Department of Physics, Presidency College, Calcutta 700073 (India); [Azad Physics Centre, Maulana Azad College, Calcutta 700013 (India)
1997-01-01T23:59:59.000Z
It is known now that chiral symmetry restoration requires the meson-nucleon couplings to be density-dependent in nuclear-matter mean-field models. We further show that, quite generally, the quark and gluon condensates in medium are related to the trace of the energy-momentum tensor of nuclear matter and in these models the incompressibility K must be less than 3 times the chemical potential {mu}. In the critical density {rho}{sub c}, the gluon condensate is only reduced by 20{percent}, indicating a larger effective nucleon mass. {copyright} {ital 1997} {ital The American Physical Society}
Screening of quark-monopole in N=4 plasma
Wei-shui Xu; Ding-fang Zeng
2014-12-11T23:59:59.000Z
We study a quark-monopole bound system moving in N=4 SYM plasma with a constant velocity by the AdS/CFT correspondence. The screening length of this system is calculated, and is smaller than that of the quark-antiquark bound state.
Charm Quark Energy Loss in QCD Matter
W. C. Xiang; H. T. Ding; D. C. Zhou; D. Rohrich
2005-07-13T23:59:59.000Z
The energy loss of heavy quarks in a quark-gluon plasma of finite size is studied within the light-cone integral approach. A simple analytical formulation of the radiative energy loss of heavy quarks is derived. This provides a convenient way to quantitatively estimate the quark energy loss. Our results show that if the energy of a heavy quark is much larger than its mass, the radiative energy loss approaches the radiative energy loss of light quarks.
Gluons and the quark sea at high energies: distributions, polarization, tomography
Boer, D.; Venugopalan, R.; Diehl, M.; Milner, R.; Vogelsang, W.; et al.
2011-09-30T23:59:59.000Z
This report is based on a ten-week program on Gluons and the quark sea at high-energies, which took place at the Institute for Nuclear Theory (INT) in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics (QCD). This report is organized around the following four major themes: (i) the spin and flavor structure of the proton, (ii) three dimensional structure of nucleons and nuclei in momentum and configuration space, (iii) QCD matter in nuclei, and (iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.
The critical indices of the Quark-Gluon Bags with Surface Tension Model with tricritical endpoint
A. I. Ivanytskyi
2011-04-11T23:59:59.000Z
The critical indices \\alpha', \\beta, \\gamma' and \\delta of the Quark Gluon Bags with Surface Tension Model with the tricritical endpoint are calculated as functions of the usual parameters of this model and two newly introduces parameters (indices). They are compared with the critical exponents of other models. It is shown that for the newly introduced indices \\chi = 0 and \\xi^T < 1 there is a branch of solutions for which the critical exponents of the present model and the statistical multifragmentation model coincide, otherwise these models belong to different universality classes. It is shown that for realistic values of the parameter \\varkappa the critical exponents \\alpha', \\beta, \\gamma' and \\delta of simple liquids and 3-dimensional Ising model can be only described by the branch of solutions in which all indices except for \\alpha' correspond to their values within the statistical multifragmentation model. The scaling relations for the found critical exponents are verified and it is demonstrated that for the standard definition of the index \\alpha' the Fisher and Griffiths scaling inequalities are not fulfilled for some values of the model parameters, whereas the Liberman scaling inequality is always obeyed. Although it is shown that the specially defined index \\alpha'_s recovers the scaling relations, another possibility, an existence of the non-Fisher universality classes, is also discussed.
Equation of state of gluon plasma from local action
Zwanziger, Daniel [New York University, New York, New York 10003 (United States)
2007-12-15T23:59:59.000Z
We review recent analytic and numerical results concerning the confinement scenario in Coulomb gauge. We then consider a local, renormalizable, BRST(Becchi-Rouet-Stora-Tyutin)-invariant action for QCD in Coulomb gauge that contains auxiliary bose and fermi ghost fields and sources. When the auxiliary fields are integrated out, one obtains the standard Coulomb gauge action with a cutoff at the Gribov horizon. We use the local formulation to calculate the leading correction to the Stefan-Boltzmann equation of state at high temperature due to the cutoff at the Gribov horizon. It is of order g{sup 6}, which is precisely the order at which the infrared divergence found by Linde divergence first occurs. No such divergence arises in the present calculation because the propagator of would-be physical gluons is suppressed in the infrared due to the proximity of the Gribov horizon in infrared directions.
Equation of State of Gluon Plasma from a Fundamental Modular Region
Zwanziger, Daniel [Physics Department, New York University, New York, New York 10003 (United States)
2005-05-13T23:59:59.000Z
Despite considerable practical success in dealing with the gluon plasma, finite-temperature perturbation theory suffers at the fundamental level from infrared divergences discovered by Linde. However, if gauge or Gribov copies are properly eliminated from the physical state space, infrared modes are strongly suppressed. We describe the gluon plasma in zeroth order as a gas of free quasiparticles with a temperature-independent dispersion relation of Gribov type, E(k)={radical}(k{sup 2}+(M{sup 4}/k{sup 2})), that results from the reduction of the physical state space. The effective mass (M{sup 2}/k) controls infrared divergences and allows finite calculable corrections. The equation of state of this gas is calculated and compared with numerical lattice data.
Collisional energy loss of heavy quarks
Alex Meistrenko; Andre Peshier; Jan Uphoff; Carsten Greiner
2013-04-13T23:59:59.000Z
We develop a transport approach for heavy quarks in a quark-gluon plasma, which is based on improved binary collision rates taking into account quantum statistics, the running of the QCD coupling and an effective screening mass adjusted to hard-thermal loop calculations. We quantify the effects of in-medium collisions by calculating the heavy flavor nuclear modification factor and the elliptic flow for RHIC energies, which are comparable to radiative effects. We also derive an analytic formula for the mean collisional energy loss of an energetic heavy quark in a streaming quark gluon plasma.
K. A. Bugaev; A. I. Ivanytskyi; D. R. Oliinychenko; E. G. Nikonov; V. V. Sagun; G. M. Zinovjev
2014-05-06T23:59:59.000Z
Here we develop the hadron resonance gas model with the Gaussian width of hadron resonances. This model allows us to treat the usual hadrons and the quark gluon bags on the same footing and to study the stability of the results obtained within different formulations of the hadron resonance gas model. In this work we perform a successful fit of 111 independent hadronic multiplicity ratios measured for $\\sqrt{s_{NN}} $= 2.7- 200 GeV. We demonstrate that in a narrow range of collision energy $\\sqrt{s_{NN}} =$ 4.3-4.9 GeV there exist peculiar irregularities in various thermodynamic quantities found at chemical freeze-out. The most remarkable irregularity is an unprecedented jump of the number of effective degrees of freedom observed in this narrow energy range which is seen in all realistic versions of the hadron resonance gas model. Therefore, the developed concept is called the non-smooth chemical freeze-out. We are arguing that these irregularities evidence for the possible formation of quark gluon bags. In order to develop other possible signals of their formation here we study the apparent width of wide hadronic resonances and quark gluon bags in a thermal environment. Two new effects generated for the wide resonances and quark gluon bags by a thermal medium are discussed here: the near threshold thermal resonance enhancement and the near threshold thermal resonance sharpening. On the basis of the new effects we argue that the most optimistic chance to find experimentally the quark gluon bags may be related to their sharpening and enhancement in a thermal medium. In this case the wide quark gluon bags may appear directly or in decays as narrow resonances that are absent in the tables of elementary particles and that have the apparent width about 50-120 MeV and the mass about or above 2.5 GeV.
ATLAS Collaboration
2014-09-19T23:59:59.000Z
A likelihood-based discriminant for the identification of quark- and gluon-initiated jets is built and validated using 4.7 fb$^{-1}$ of proton-proton collision data at $\\sqrt{s}$ = 7 TeV collected with the ATLAS detector at the LHC. Data samples with enriched quark or gluon content are used in the construction and validation of templates of jet properties that are the input to the likelihood-based discriminant. The discriminating power of the jet tagger is established in both data and Monte Carlo samples within a systematic uncertainty of 10-20%. In data, light-quark jets can be tagged with an efficiency of 50% while achieving a gluon-jet mis-tag rate of 25% in a $p_T$ range between 40 GeV and 360 GeV for jets in the acceptance of the tracker. The rejection of gluon-jets found in the data is significantly below what is attainable using a Pythia 6 Monte Carlo simulation, where gluon-jet mis-tag rates of 10% can be reached for a 50% selection efficiency of light-quark jets using the same jet properties.
A T-Matrix Approach to Heavy Quark Interaction with Thermal Gluons in a Quark Gluon Plasma
Huggins, Kyle
2012-10-19T23:59:59.000Z
!1!2T p 2!32!4j 2(2 )4 (4)(p3 + p4 p1 p2): (3.2) Here, mi refers to the mass of the incoming/outgoing particles. These two equations identically describe a boson-fermion interaction, with the unique physics tied into a general scattering... in the Born series. That is, instead of iterating Eq. (1.11), T = V + V G0V + V G0V G0V + ; (1.22) I numerically solve for T by inverting the matrix element (1 V G0). I now reproduce part of the derivation from [6] to see how the drag coe cient...
Shear viscosity of the gluon plasma in the stochastic-vacuum approach
Dmitri Antonov
2009-05-20T23:59:59.000Z
Shear viscosity of the gluon plasma in SU(3) YM theory is calculated nonperturbatively, within the stochastic vacuum model. The result for the ratio of the shear viscosity to the entropy density, proportional to the squared chromo-magnetic gluon condensate and the fifth power of the correlation length of the chromo-magnetic vacuum, falls off with the increase of temperature. At temperatures larger than the deconfinement critical temperature by a factor of 2, this fall-off is determined by the sixth power of the temperature-dependent strong-coupling constant and yields an asymptotic approach to the conjectured lower bound of 1/(4\\pi), achievable in {\\cal N}=4 SYM theory. As a by-product of the calculation, we find a particular form of the two-point correlation function of gluonic field strengths, which is the only one consistent with the Lorentzian shape of the shear-viscosity spectral function.
Nuclear Physics A 757 (2005) 127 Quarkgluon plasma and color glass condensate at
Nuclear Physics A 757 (2005) 1Â27 QuarkÂgluon plasma and color glass condensate at RHIC hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A particular focus, the so-called quarkÂgluon plasma (QGP). We also discuss evidence for a possible precursor state
Hadronic modes and quark properties in the quark-gluon plasma
Mannarelli, M.; Rapp, Ralf.
2005-01-01T23:59:59.000Z
induces quasiparticle masses of up to 150 MeV, whereas the attractive color-singlet part generates resonance structures in the q-q T matrix, which in turn lead to quasiparticle widths of similar to 200 MeV. This corresponds to scattering rates of similar...
Heavy quark production from jet conversions in a quark-gluon plasma
Liu, W.; Fries, Rainer J.
2008-01-01T23:59:59.000Z
. Rev. C 71, 034907 (2005). [12] W. Liu, C. M. Ko, and B.W. Zhang, Phys. Rev. C 75, 051901(R) (2007); Int. J. Mod. Phys. E 16, 1930 (2007). [13] R. J. Fries, B. Muller, and D. K. Srivastava, Phys. Rev. Lett. 90, 132301 (2003); D. K. Srivastava, C...), Phys. Rev. Lett. 97, 152301 (2005). [16] S. Sapeta and U. A. Wiedemann, Eur. Phys. J. C 55, 293 (2008). [17] B. Svetitsky, Phys. Rev. D 37, 2484 (1988). [18] J. P. Blaizot and E. Iancu, Phys. Rep. 359, 355 (2002). [19] H. van Hees, V. Greco, and R...
Chiu, T W; Chiu, Ting-Wai; Hsieh, Tung-Han
2003-01-01T23:59:59.000Z
We determine several quantities in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with Wilson gauge action at $ \\beta = 6.0 $ on the $ 16^3 \\times 32 $ lattice, we compute quenched quark propagators for 13 bare quark masses. The pion decay constant is extracted from the pion propagator, and from which the inverse lattice spacing is determined to be $ a^{-1} = 1.979(6) $ GeV. The parameters ($ C, \\delta, B $) in the pseudoscalar meson mass formula in quenched chiral perturbation theory (q$\\chi$PT) to one-loop order are determined. Further, we measure the index (topological) susceptibility of these 100 gauge configurations, $ \\chi_t = (175 \\pm 6 {MeV})^4 $, from which we obtain an estimate of the mass of $ \\eta' $ in q$\\chi$PT, and the coefficient of quenched chiral logarithm, both in good agreement with the values determined from the pion masses, as well as with the theoretical estimates. With our values of $ C, \\delta, B $, the experimental inputs of pion and kaon mass...
Total cross section of neutron-proton scattering at low energies in quark-gluon model
V. A. Abramovsky; N. V. Radchenko
2011-07-30T23:59:59.000Z
We show that analysis of nonrelativistic neutron-proton scattering in a framework of relativistic QCD based quark model can give important information about QCD vacuum structure. In this model we describe total cross section of neutron-proton scattering at kinetic energies of projectile neutron from 1 eV up to 1 MeV.
On the role of gluons and the quark sea in the proton spin
Zavada, Petr
2015-01-01T23:59:59.000Z
The real, interacting elementary particle always consits of a 'bare' particle and a cloud of virtual particles mediating a self-interaction and/or the binding inside a composite object. In this note we discuss the question of spin content of the virtual cloud in two different cases: electron and quark.
On Relation Between the Quark Gluon Bag Surface Tension and the Colour Tube String Tension
K. A. Bugaev; G. M. Zinovjev
2010-05-17T23:59:59.000Z
Here we revisit the bag phenomenology of the deconfining phase transition to replenish it by introducing systematically the bag surface tension. Comparing the free energy of such bags and that one of the strings confining the static quark-antiquark pair, we express the string tension in terms of the bag surface tension and thermal pressure in order to estimate the bag characteristics using the lattice QCD data. Our analysis of the bag entropy density demonstrates that the surface tension coefficient is amazingly negative at the cross-over (continuous transition). This approach allows us to naturally account for an appearance of a very pronounced maximum (observed in the lattice QCD simulations) of the entropy of the bound static quark-antiquark pair. The vicinity of the (tri)critical endpoint is also analyzed to clarify the meaning of vanishing surface tension coefficient.
Equation of State and Viscosities from a Gravity Dual of the Gluon Plasma
R. Yaresko; B. Kampfer
2014-12-02T23:59:59.000Z
Employing new precision data of the equation of state of the SU(3) Yang-Mills theory (gluon plasma) the dilaton potential of the gravity dual is adjusted in the temperature range $(1 - 10) T_c$ in a bottom-up approach. The ratio of bulk viscosity to shear viscosity follows then as $\\zeta/\\eta \\approx \\pi \\Delta v_s^2$ for $\\Delta v_s^2 maximum value of 0.95 at $\\Delta v_s^2 \\approx 0.32$, where $\\Delta v_s^2$ is the non-conformality measure, while the ratio of shear viscosity to entropy density is known as $(4 \\pi)^{-1}$ for the considered set-up with Hilbert action on the gravity side.
Geek-Up[12.03.2010]: Halomonadaceae Bacteria and the Return of Quark Gluon
Broader source: Energy.gov (indexed) [DOE]
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742Energy ChinaofSchaefer To: Congestion StudyForecasting. |OctoberNiketa Kumar NiketaPlasma |
Proton structure and tensor gluons
George Savvidy
2014-07-31T23:59:59.000Z
We consider a possibility that inside the proton and, more generally, inside the hadrons there are additional partons - tensor-gluons, which can carry a part of the proton momentum. The tensor-gluons have zero electric charge, like gluons, but have a larger spin. Inside the proton a nonzero density of the tensor-gluons can be generated by the emission of tensor-gluons by gluons. The last mechanism is typical for non-Abelian tensor gauge theories, in which there exists a gluon-tensor-tensor vertex of order g. Therefore the number of gluons changes not only because a quark may radiate a gluon or because a gluon may split into a quark-antiquark pair or into two gluons, but also because a gluon can split into two tensor-gluons. The process of gluon splitting suggests that part of the proton momentum which was carried by neutral partons is shared between vector and tensor gluons. We derive evolution equations for the parton distribution functions which take into account these new processes. The momentum sum rule allows to find the tensor-gluons contribution to the Callan-Simanzik beta function and to calculate the corresponding anomalous dimensions. This contribution changes the behavior of the structure functions, and the logarithmic correction to the Bjorken scaling becomes more mild. This also influences the unification scale at which the coupling constants of the Standard Model merge, shifting its value to lower energies of order of 40 TeV.
Langevin dynamics and decoherence of heavy quarks at high temperatures
Akamatsu, Yukinao
2015-01-01T23:59:59.000Z
Langevin equation of heavy quarks in high-temperature quark-gluon plasma is derived. The dynamics of heavy quark color is coupled with the phase space dynamics and causes a macroscopic superposition state of heavy quark momentum. Decoherence of the superposition state allows us classical description. The time scale of decoherence gives an appropriate discretization time scale $\\Delta t \\sim \\sqrt{M/\\gamma}$ for the classical Langevin equation, where $M$ is heavy quark mass and $\\gamma$ is heavy quark momentum diffusion constant.
Self-consistent quasi-particle model for relativistic plasma
Vishnu M. Bannur
2006-02-24T23:59:59.000Z
Relativistic plasma with radiation at thermodynamic equilibrium is ageneral system of interest in astrophysics and high energy physics. We develop a new self-consistent quasi-particle model for such a system to take account of collective behaviour of plasma andthermodynamic properties are derived. It is applied to electrodynamic plasma and quark gluon plasma and compared with existing results.
EN YO,H.; SAITO,N.; SHIBATA,T.A.; YAZAKI,K.; BUNCE,G.
2002-03-29T23:59:59.000Z
The RIKEN School on ''Quark-Gluon Structure of the Nucleon and QCD'' was held from March 29th through 31st at the Nishina Memorial Hall of RIKEN, Wako, Saitama, Japan, sponsored by RIKEN (the Institute of Physical and Chemical Research). The school was the second of a new series with a broad perspective of hadron and nuclear physics. The purpose of the school was to offer young researchers an opportunity to learn theoretical aspects of hadron physics based on QCD and related experimental programs being or to be carried out by Japanese groups. We had 3 theoretical courses, each consisting of 3 one-hour lectures, and 6 experimental courses, each consisting of a one-hour lecture.
Abbiendi, G; Åkesson, P F; Alexander, G; Allison, J; Amaral, P; Anagnostou, G; Anderson, K J; Asai, S; Axen, D A; Azuelos, Georges; Bailey, I; Barberio, E; Barillari, T; Barlow, R J; Batley, J Richard; Bechtle, P; Behnke, T; Bell, K W; Bell, P J; Bella, G; Bellerive, A; Benelli, G; Bethke, Siegfried; Biebel, O; Boeriu, O; Bock, P; Boutemeur, M; Braibant, S; Brigliadori, L; Brown, R M; Büsser, K; Burckhart, H J; Campana, S; Carnegie, R K; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Ciocca, C; Csilling, Akos; Cuffiani, M; Dado, S; de Roeck, A; De Wolf, E A; Desch, Klaus; Dienes, B; Donkers, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Etzion, E; Fabbri, Franco Luigi; Feld, L; Ferrari, P; Fiedler, F; Fleck, I; Ford, M; Frey, A; Gagnon, P; Gary, J W; Gaycken, G; Geich-Gimbel, C; Giacomelli, G; Giacomelli, P; Giunta, M; Goldberg, J; Gross, E; Grunhaus, Jacob; Gruwé, M; Günther, P O; Sen-Gupta, A; Hajdu, C; Hamann, M; Hanson, G G; Harel, A; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Herten, G; Heuer, R D; Hill, J C; Hoffman, K; Horváth, D; Igo-Kemenes, P; Ishii, K; Jeremie, H; Jovanovic, P; Junk, T R; Kanaya, N; Kanzaki, J; Karlen, Dean A; Kawagoe, K; Kawamoto, T; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Kluth, S; Kobayashi, T; Kobel, M; Komamiya, S; Kramer, T; Krieger, P; Von Krogh, J; Krüger, K; Kühl, T; Kupper, M; Lafferty, G D; Landsman, Hagar Yaël; Lanske, D; Layter, J G; Lellouch, D; Letts, J; Levinson, L; Lillich, J; Lloyd, S L; Loebinger, F K; Lü, J; Ludwig, A; Ludwig, J; Mader, W; Marcellini, S; Martin, A J; Masetti, G; Mashimo, T; Mättig, P; McKenna, J A; McPherson, R A; Meijers, F; Menges, W; Merritt, F S; Mes, H; Meyer, N; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Moed, S; Mohr, W; Mori, T; Mutter, A; Nagai, K; Nakamura, I; Nanjo, H; Neal, H A; Nisius, R; O'Neale, S W; Oh, A; Oreglia, M J; Orito, S; Pahl, C; Pásztor, G; Pater, J R; Pilcher, J E; Pinfold, J L; Plane, D E; Poli, B; Pooth, O; Przybycien, M B; Quadt, A; Rabbertz, K; Rembser, C; Renkel, P; Roney, J M; Rozen, Y; Runge, K; Sachs, K; Saeki, T; Sarkisyan-Grinbaum, E; Schaile, A D; Schaile, O; Scharff-Hansen, P; Schieck, J; Schörner-Sadenius, T; Schröder, M; Schumacher, M; Scott, W G; Seuster, R; Shears, T G; Shen, B C; Sherwood, P; Skuja, A; Smith, A M; Sobie, R J; Söldner-Rembold, S; Spanó, F; Stahl, A; Strom, D; Ströhmer, R; Tarem, S; Tasevsky, M; Teuscher, R; Thomson, M A; Torrence, E; Toya, D; Tran, P; Trigger, I; Trócsányi, Z L; Tsur, E; Turner-Watson, M F; Ueda, I; Ujvári, B; Vollmer, C F; Vannerem, P; Vertesi, R; Verzocchi, M; Voss, H; Vossebeld, Joost Herman; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wengler, T; Wermes, N; Wilson, G W; Wilson, J A; Wolf, G; Wyatt, T R; Yamashita, S; Zer-Zion, D; Zivkovic, L
2004-01-01T23:59:59.000Z
Flavour inclusive, udsc and b fragmentation functions in unbiased jets, and flavour inclusive, udsc, b and gluon fragmentation functions in biased jets are measured in e+e- annihilations from data collected at centre-of-mass energies of 91.2, and 183-209 GeV with the OPAL detector at LEP. The unbiased jets are defined by hemispheres of inclusive hadronic events, while the biased jet measurements are based on three-jet events selected with jet algorithms. Several methods are employed to extract the fragmentation functions over a wide range of scales. Possible biases are studied in the results are obtained. The fragmentation functions are compared to results from lower energy e+e- experiments and with earlier LEP measurements and are found to be consistent. Scaling violations are observed and are found to be stronger for the fragmentation functions of gluon jets than for those of quarks. The measured fragmentation functions are compared to three recent theoretical next-to-leading order calculations and to the p...
Lance Labun; Jan Rafelski
2010-10-10T23:59:59.000Z
Understanding physics in domains of critical (quantum unstable) fields requires investigating the classical and quantum particle dynamics at the critical acceleration, $\\dot u \\to 1$ [natural units]. This regime of physics remains today experimentally practically untested. Particle and light collision experiments reaching critical acceleration are becoming feasible, in particular applying available high intensity laser technology. Ultra-relativistic heavy ion collisions breach the critical domain but are complicated by the presence of much other physics. The infamous problem of radiation reaction and the challenging environment of quantum vacuum instability arising in the high field domain signal the need for a thorough redress of the present theoretical framework.
Consistency of Perfect Fluidity and Jet Quenching in semi-Quark-Gluon Monopole Plasmas
Jiechen Xu; Jinfeng Liao; Miklos Gyulassy
2015-03-31T23:59:59.000Z
We utilize a new framework, CUJET3.0, to deduce the energy and temperature dependence of jet transport parameter, $\\hat{q}(E>10\\; {\\rm GeV},T)$, from a combined analysis of available data on nuclear modification factor and azimuthal asymmetries from RHIC/BNL and LHC/CERN on high energy nuclear collisions. Extending a previous perturbative-QCD based jet energy loss model (known as CUJET2.0) with (2+1)D viscous hydrodynamic bulk evolution, this new framework includes three novel features of nonperturbative physics origin: (1) the Polyakov loop suppression of color-electric scattering (aka "semi-QGP" of Pisarski et al) and (2) the enhancement of jet scattering due to emergent magnetic monopoles near $T_c$ (aka "magnetic scenario" of Liao and Shuryak) and (3) thermodynamic properties constrained by lattice QCD data. CUJET3.0 reduces to v2.0 at high temperatures $T > 400$ MeV, but greatly enhances $\\hat{q}$ near the QCD deconfinement transition temperature range. This enhancement accounts well for the observed elliptic harmonics of jets with $p_T>10$ GeV. Extrapolating our data-constrained $\\hat{q}$ down to thermal energy scales, $E \\sim 2$ GeV, we find for the first time a remarkable consistency between high energy jet quenching and bulk perfect fluidity with $\\eta/s\\sim T^3/\\hat{q} \\sim 0.1$ near $T_c$.
Geek-Up[11.05.10]: Quark Gluon Plasma, Solar-Power Generating...
Office of Environmental Management (EM)
auditorium at 2 a.m. EDT July 4 and waited for the latest announcement regarding the Higgs boson. When CERN Director-General Rolf-Dieter Heuer said the words - "I think we have it"...
Vector screening masses in the quark-gluon plasma and their physical significance
B. B. Brandt; A. Francis; M. Laine; H. B. Meyer
2014-08-25T23:59:59.000Z
Static and non-static thermal screening states that couple to the conserved vector current are investigated in the high-temperature phase of QCD. Their masses and couplings to the current are determined at weak coupling, as well as using two-flavor lattice QCD simulations. A consistent picture emerges from the comparison, providing evidence that non-static Matsubara modes can indeed be treated perturbatively. We elaborate on the physical significance of the screening masses.
Geek-Up[11.05.10]: Quark Gluon Plasma, Solar-Power Generating Windows and
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your Density Isn't YourTransport inEnergy0.pdfTechnologiesNATIONAL003 IntellectualSECCS Field Studies |
Drag and jet quenching of heavy quarks in a strongly coupled N=2* plasma
Carlos Hoyos-Badajoz
2009-09-14T23:59:59.000Z
The drag of a heavy quark and the jet quenching parameter are studied in the strongly coupled N=2* plasma using the AdS/CFT correspondence. Both increase in units of the spatial string tension as the theory departs from conformal invariance. The description of heavy quark dynamics using a Langevin equation is also considered. It is found that the difference between the velocity dependent factors of the transverse and longitudinal momentum broadening of the quark admit an interpretation in terms of relativistic effects, so the distribution is spherical in the quark rest frame. When conformal invariance is broken there is a broadening of the longitudinal momentum distribution. This effect may be useful in understanding the jet distribution observed in experiments.
Effect of thermalized charm on heavy quark energy loss
Souvik Priyam Adhya; Mahatsab Mandal; Sreemoyee Sarkar; Pradip K. Roy; Sukalyan Chattopadhyay
2014-08-28T23:59:59.000Z
The recent experimental results on the flow of $J/\\psi$ at LHC show that ample amount of charm quarks is present in the quark gluon plasma and probably they are thermalized. In the current study we investigate the effect of thermalized charm quarks on the heavy quark energy loss to leading order in the QCD coupling constant. It is seen that the energy loss of charm quark increases considerably due to the inclusion of thermal charm quarks. Running coupling has also been implemented to study heavy quark energy loss and we find substantial increase in the heavy quark energy loss due to heavy-heavy scattering at higher temperature to be realized at LHC energies.
Energy Loss of Heavy Quarks in a QGP with a Running Coupling Constant Approach
Pol B. Gossiaux; Joerg Aichelin
2009-09-23T23:59:59.000Z
We show that the effective running coupling constant, $\\alpha_{\\rm eff}$, and the effective regulator, $\\kappa \\tilde{m}_{D}^2$, which we used recently to calculate the energy loss, $\\frac{dE}{dx}$, and the elliptic flow, $v_2$, of heavy quarks in an expanding quark gluon plasma plasma (QGP) are compatible with lattice results and with recently advanced analytical pQCD calculation.
Static quark anti-quark free and internal energy in 2-flavor QCD and bound states in the QGP
O. Kaczmarek; F. Zantow
2005-10-21T23:59:59.000Z
We present results on heavy quark free energies in 2-flavour QCD. The temperature dependence of the interaction between static quark anti-quark pairs will be analyzed in terms of temperature dependent screening radii, which give a first estimate on the medium modification of (heavy quark) bound states in the quark gluon plasma. Comparing those radii to the (zero temperature) mean squared charge radii of cha rmonium states indicates that the $J/\\psi$ may survive the phase transition as a bound state, while $\\chi_c$ and $\\psi'$ are expected to show significant thermal modifications at temperatures close to the transition. Furthermore we will analyze the relation between heavy quark free energies, entropy contributions and internal energy and discuss their relation to potential models used to analyze the melting of heavy quark bound states above the deconfinement temperature. Results of different groups and various potential models for bound states in the deconfined phase of QCD are compared.
Nonabelian plasma instabilities in Bjorken expansion
Anton Rebhan
2008-10-17T23:59:59.000Z
Plasma instabilities are parametrically the dominant nonequilibrium dynamics of a weakly coupled quark-gluon plasma. In recent years the time evolution of the corresponding collective colour fields has been studied in stationary anisotropic situations. Here I report on recent numerical results on the time evolution of the most unstable modes in a longitudinally expanding plasma as they grow from small rapidity fluctuations to amplitudes where non-Abelian self-interactions become important.
Relation between quark-antiquark potential and quark-antiquark free energy in hadronic matter
Zhen-Yu Shen; Xiao-Ming Xu
2015-07-07T23:59:59.000Z
In the high-temperature quark-gluon plasma and its subsequent hadronic matter created in a high-energy nucleus-nucleus collision, the quark-antiquark potential depends on the temperature. The temperature-dependent potential is expected to be derived from the free energy obtained in lattice gauge theory calculations. This requires one to study the relation between the quark-antiquark potential and the quark-antiquark free energy. When the system's temperature is above the critical temperature, the potential of a heavy quark and a heavy antiquark almost equals the free energy, but the potential of a light quark and a light antiquark, of a heavy quark and a light antiquark and of a light quark and a heavy antiquark is substantially larger than the free energy. When the system's temperature is below the critical temperature, the quark-antiquark free energy can be taken as the quark-antiquark potential. This allows one to apply the quark-antiquark free energy to study hadron properties and hadron-hadron reactions in hadronic matter.
Gluon Radiation in Top Production and Decay
Cosmin Macesanu; Lynne H. Orr
2000-01-14T23:59:59.000Z
We present the results of an exact calculation of gluon radiation in top production and decay at high energy electron-positron colliders. We include all spin correlations and interferences, the bottom quark mass, and finite top width effects in the matrix element calculation. We study properties of the radiated gluons and implications for top mass measurement.
R. B. Neufeld; Ivan Vitev; Hongxi Xing
2014-01-20T23:59:59.000Z
We present an operator definition of the collisional energy and momentum loss suffered by an energetic charged particle in the presence of a medium. Our approach uses the energy-momentum tensor of the medium to evaluate the energy and momentum transfer rates. We apply this formalism to an energetic lepton or quark propagating in thermal electron-positron or quark-gluon plasmas, respectively. By using two different approaches to describe the energetic charged particle, an external current approach and a diagrammatic approach, we show explicitly that the operator method reproduces the known results for collisional energy loss from the scattering rate formalism. We further use our results to evaluate the collisional energy and momentum loss for the cases of heavy quark propagation through a quark-gluon plasma and energetic muon propagation in an electron-positron plasma produced in a high-intensity laser field.
A. K. Chaudhuri
2008-07-04T23:59:59.000Z
We have developed a hydrodynamic model to study sequential melting of charmonium states in an expanding QGP medium. According to the initial fluid temperature profile, $J/\\psi$'s are randomly distributed in the transverse plane. As the fluid evolve in time, the free streaming $J/\\psi$'s are suppressed if the local fluid temperature exceed a critical temperature. PHENIX data on the centrality dependence of $J/\\psi$ suppression in Au+Au collisions at mid-rapidity are explained by sequential melting of the charmonium states, $\\chi_c$, $\\psi\\prime$ and $J/\\psi$, in the expanding medium. The critical temperatures $T_{J/\\psi} \\approx2.09T_c$ and $T_\\chi=T_{\\chi_c}=T_{\\psi\\prime} \\approx 1.1T_c$ agree with lattice motivated calculations. The feed-down fraction $F$ depend on whether the cold nuclear matter effect is included or not. It changes from $F=0.3$ with cold nuclear matter effect included to $F=0.5$ when the effect is neglected. Model fails to reproduce the PHENIX data on the centrality dependence of $J/\\psi$ suppression in Cu+Cu collisions at mid-rapidity, indicating that the mechanism of $J/\\psi$ suppression is different in Au+Au and in Cu+Cu collisions. We also use the model to predict for the centrality dependence of $J/\\psi$ suppression in Pb+Pb collisions at LHC energy, $\\sqrt{s}$=5500 GeV. In LHC energy, $J/\\psi$'s are more suppressed in mid central collisions than in Au+Au collisions at RHIC energy.
Hong, Juhee
We compute the nonequilibrium stress tensor induced by a heavy quark moving through weakly coupled QCD plasma at the speed of light and compare the result to N=4 super-Yang-Mills theory at strong coupling. The QCD Boltzmann ...
Y. Maezawa; T. Umeda; S. Aoki; S. Ejiri; T. Hatsuda; K. Kanaya; H. Ohno
2012-10-24T23:59:59.000Z
Free energies between static quarks and Debye screening masses in the quark-gluon plasma are studied on the basis of Polyakov-line correlations in lattice simulations of 2+1 flavors QCD with the renormalization-group improved gluon action and the $O(a)$-improved Wilson quark action. We perform simulations at $m_{\\rm PS}/m_{\\rm V} = 0.63$ (0.74) for light (strange) flavors with lattice sizes of $32^3 \\times N_t$ with $N_t=4$--12. We adopt the fixed-scale approach, where temperature can be varied without changing the spatial volume and renormalization factor. We find that, at short distance, the free energies of static quarks in color-singlet channel converge to the static-quark potential evaluated from the Wilson-loop at zero-temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the free energies of static quarks approach to twice the single-quark free energies, implying that the interaction between static quarks is fully screened. The screening properties can be well described by the screened Coulomb form with appropriate Casimir factor at high temperature. We also discuss a limitation of the fixed-scale approach at high temperature.
QCD thermodynamics with Wilson quarks at large kappa
Tom Blum; Thomas A. DeGrand; Carleton DeTar; Steven Gottlieb; A. Hasenfratz; Leo Karkkainen; D. Toussaint; R. L. Sugar
1994-04-12T23:59:59.000Z
We have extended our study of the high temperature transition with two flavors of Wilson quarks on 12^3 x 6 lattices to kappa=0.19. We have also performed spectrum calculations on 12^3 x 24 lattices at kappa=0.19 to find the physical lattice spacing and quark mass. At this value of kappa the transition is remarkable in that the plaquette and psi-bar-psi show a large discontinuity while the Polyakov loop changes very little. This and several other features of the transition are more suggestive of a bulk transition than a transition to a quark-gluon plasma. However, if the temperature is estimated using the rho mass as a standard, the result is about 150 MeV, in agreement with the value found for the thermal transition with Kogut-Susskind quarks. uuencoded compressed Postscript file
van Hees, H.; Greco, V.; Rapp, Ralf.
2006-01-01T23:59:59.000Z
strongly interacting QGP (sQGP), as well as parton coalescence, can play an essential role in the interpretation of recent data from the BNL Relativistic Heavy-Ion Collider (RHIC), and thus illuminate the nature of the sQGP and its hadronization. Our main...
van Hees, H.; Greco, V.; Rapp, Ralf.
2006-01-01T23:59:59.000Z
. Tai et al. (STAR Collaboration), J. Phys. G 30, S809 (2004). [34] J. Dunkel and P. Ha?nggi, Phys. Rev. E 71, 016124 (2005). [35] P. Arnold, Phys. Rev. E 61, 6099 (2000). [36] X. Dong et al., Phys. Lett. B597, 328 (2004). [37] V. Greco, C. M. Ko...
Parton energy loss due to synchrotron-like gluon emission
B. G. Zakharov
2008-09-03T23:59:59.000Z
We develop a quasiclassical theory of the synchrotron-like gluon radiation. Our calculations show that the parton energy loss due to the synchrotron gluon emission may be important in the jet quenching phenomenon if the plasma instabilities generate a sufficiently strong chromomagnetic field. Our gluon spectrum disagrees with that obtained by Shuryak and Zahed within the Schwinger's proper time method.
Fully nonlinear excitations of non-Abelian plasma
Vishnu M. Bannur
2007-06-06T23:59:59.000Z
We investigate fully nonlinear, non-Abelian excitations of quark-antiquark plasma, using relativistic fluid theory in cold plasma approximation. There are mainly three important nonlinearities, coming from various sources such as non-Abelian interactions of Yang-Mills (YM) fields, Wong's color dynamics and plasma nonlinearity, in our model. By neglecting nonlinearities due to plasma and color dynamics we get back the earlier results of Blaizot {\\it et. al.}, Phys. Rev. Lett. 72, 3317 (1994). Similarly, by neglecting YM fields nonlinearity and plasma nonlinearity, it reduces to the model of Gupta {\\it et. al.}, Phys. Lett. B498, 223 (2005). Thus we have the most general non-Abelian mode of quark-gluon plasma (QGP). Further, our model resembles the problem of propagation of laser beam through relativistic plasma, Physica 9D, 96 (1983). in the absence of all non-Abelian interactions.
Gluon sivers and experimental considerations for TMDs
Thomas Burton
2012-12-14T23:59:59.000Z
The study and characterisation of transverse-momentum-dependent distribution functions (TMDs) is a major goal of the Electron-Ion Collider (EIC) physics programme. The study of gluon TMDs poses a greater challenge than for quark TMDs in DIS measurements, as gluons do not directly couple to photons. The study of D meson pairs has been proposed to provide access to gluon TMDs, but is demanding due to the rarity of D production. Here, we discuss the feasibility of such a measurement, and touch upon wider issues to be considered when measuring TMDs at the EIC.
The diagonal and off-diagonal quark number susceptibility of high temperature and finite density QCD
Ari Hietanen; Kari Rummukainen
2008-04-29T23:59:59.000Z
We study the quark number susceptibility of the hot quark-gluon plasma at zero and non-zero quark number density, using lattice Monte Carlo simulations of an effective theory of QCD, electrostatic QCD (EQCD). Analytic continuation is used to obtain results at non-zero quark chemical potential. We measure both flavor singlet (diagonal) and non-singlet (off-diagonal) quark number susceptibilities. The diagonal susceptibility approaches the perturbative result above 20T_c, but below that temperature we observe significant deviations. The results agree well with 4d lattice data down to temperatures 2T_c. The off-diagonal susceptibility is more prone to statistical and systematic errors, but the results are consistent with perturbation theory already at 10T_c.
Harald Dorn; Thanh Hai Ngo
2007-07-26T23:59:59.000Z
We study the effect of the relative S^5-angle of a quark and an antiquark on their static potential and the related screening length in a strongly coupled moving ${\\cal N}=4$ SYM plasma. The large velocity scaling law for the screening length holds for any relative S^5-angle $\\theta$. However, the velocity independent prefactor Z strongly depends on $\\theta$. For comparison with QCD we propose to average Z over all relative orientations on S^5. This generates a suppression factor relative to the case $\\theta =0$.
Sambamurti Memorial Lecture: Spotlight on the Gluon
Michael Begelas
2010-09-01T23:59:59.000Z
Begel uses results from the Fermilab D0 and E706 experiments to explain how the production rate and energy spectrum of photons produced during proton collisions helped to clarify how the energy inside the proton is shared between quarks and gluons.
Exotic hybrid mesons with light quarks
Claude Bernard; Tom Blum; Thomas A. DeGrand; Carleton DeTar; Steven Gottlieb; Urs. M. Heller; Jim Hetrick; Craig McNeile; Kari Rummukainen; Bob Sugar; Doug Toussaint; Matt Wingate
1996-07-12T23:59:59.000Z
Hybrid mesons, made from a quark, an antiquark and gluons, can have quantum numbers inaccessible to conventional quark-antiquark states. Confirmation of such states would give information on the role of "dynamical" color in low energy QCD. We present preliminary results for hybrid meson masses using light Wilson valence quarks.
U. Jamil; J. K. Sarma
2007-12-01T23:59:59.000Z
Evolution of gluon distribution function from Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equation in next-to-leading order (NLO) at low-x is presented assuming the Regge behaviour of quarks and gluons at this limit. We compare our results of gluon distribution function with MRST2004, GRV98LO and GRV98NLO parameterizations and show the compatibility of Regge behaviour of quark and gluon distribution functions with perturbative quantum chromodynamics (PQCD) at low-x.
Transport coefficients of heavy quarks around $T_c$ at finite quark chemical potential
H. Berrehrah; P. B. Gossiaux; J. Aichelin; W. Cassing; J. M. Torres-Rincon; E. Bratkovskaya
2014-06-20T23:59:59.000Z
The interactions of heavy quarks with the partonic environment at finite temperature $T$ and finite quark chemical potential $\\mu_q$ are investigated in terms of transport coefficients within the Dynamical Quasi-Particle model (DQPM) designed to reproduce the lattice-QCD results (including the partonic equation of state) in thermodynamic equilibrium. These results are confronted with those of nuclear many-body calculations close to the critical temperature $T_c$. The hadronic and partonic spatial diffusion coefficients join smoothly and show a pronounced minimum around $T_c$, at $\\mu_q=0$ as well as at finite $\\mu_q$. Close and above $T_c$ its absolute value matches the lQCD calculations for $\\mu_q=0$. The smooth transition of the heavy quark transport coefficients from the hadronic to the partonic medium corresponds to a cross over in line with lattice calculations, and differs substantially from perturbative QCD (pQCD) calculations which show a large discontinuity at $T_c$. This indicates that in the vicinity of $T_c$ dynamically dressed massive partons and not massless pQCD partons are the effective degrees-of-freedom in the quark-gluon plasma.
Thermal charm production in a quark-gluon plasma in Pb-Pb collisions at root S(NN)=5.5 TeV
Zhang, Ben-Wei; Ko, Che Ming; Liu, Wei.
2008-01-01T23:59:59.000Z
. Wetzorke, Phys. Rev. D 69, 094507 (2004). [8] B. Zhang, C. M. Ko, B. A. Li, Z. W. Lin, and B. H. Sa, Phys. Rev. C 62, 054905 (2000); B. Zhang, C. M. Ko, B. A. Li, Z. W. Lin, and S. Pal, ibid. 65, 054909 (2002). [9] H. Satz, J. Phys. G 32, R25 (2006...). [10] L. Grandchamp, S. Lumpkins, D. Sun, H. van Hees, and R. Rapp, Phys. Rev. C 73, 064906 (2006). [11] R. L. Thews and M. L. Mangano, Phys. Rev. C 73, 014904 (2006). [12] A. Andronic, P. Braun-Munzinger, K. Redlich, and J. Stachel, Phys. Lett. B...
U. Jamil; J. K. Sarma
2005-08-05T23:59:59.000Z
In this paper t and x-evolutions of gluon distribution function from Dokshitzer-Gribov-Lipatov-Altarelli-Parisi(DGLAP) evolution equation in leading order(LO) at low-x, assuming the Regge behaviour of quark and gluon at this limit, are presented. We compare our results of gluon distribution function with MRST 2001, MRST 2004 and GRV '98 parameterizations and show the compatibility of Regge behaviour of quark and gluon distribution functions with perturbative quantum chromodynamics(PQCD) at low-x. We also discuss the limitations of Taylor series expansion method used earlier to solve DGLAP evolution equations, in the Regge behaviour of distribution functions.
Single top quark production at D0
Reinhard Schwienhorst; for the D0 collaboration
2011-09-13T23:59:59.000Z
Updates of electroweak single top quark production measurements by the D0 collaboration are presented using 5.4fb^-1 of proton-antiproton collision data from the Tevatron at Fermilab. Measurements of the t-channel, s-channel and combined single top quark production cross section are presented, including an updated lower limit on the CKM matrix element |V_tb|. Also reported are results from searches for gluon-quark flavor-changing neutral currents and W' boson production.
Quark hadronization probed by K(0) mesons
Baringer, Philip S.
1990-04-01T23:59:59.000Z
are well understood in the context of QCD. A quark-antiquark pair with large virtuality (or qz) evolves through a parton shower of quarks and gluons of decreas- ing virtuality. So long as the parton virtuality is large, a, is small and the perturbative... /CP) is given in Fig. 7(a) for tracks opposite the D' tag. These tracks come from the fragmentation of a known 14.5-GeV c (or c) 200 (a)Vebber 4. 1 —c quark events Lund 6.3 — c quark events R(Ko/Charged) opposite D tag 100 (b) WEBBER 4.1: u quark...
Nonzero Mean Squared Momentum of Quarks in the Non-Perturbative QCD Vacuum
Li-Juan Zhou; Leonard S. Kisslinger; Wei-xing Ma
2010-04-21T23:59:59.000Z
The non-local vacuum condensates of QCD describe the distributions of quarks and gluons in the non-perturbative QCD vacuum. Physically, this means that vacuum quarks and gluons have nonzero mean-squared momentum, called virtuality. In this paper we study the quark virtuality which is given by the ratio of the local quark-gluon mixed vacuum condensate to the quark local vacuum condensate. The two vacuum condensates are obtained by solving Dyson-Schwinger Equations of a fully dressed quark propagator with an effective gluon propagator. Using our calculated condensates, we obtain the virtuality of quarks in the QCD vacuum state. Our numerical predictions differ from the other theoretical model calculations such as QCD sum rules, Lattice QCD and instanton models.
Exploration of nucleon structure in lattice QCD with chiral quarks
Syritsyn, Sergey Nikolaevich
2010-01-01T23:59:59.000Z
In this work, we calculate various nucleon structure observables using the fundamental theory of quarks and gluons, QCD, simulated on a lattice. In our simulations, we use the full QCD action including Nf = 2+ 1 dynamical ...
Gluon Polarisation Measurements @ COMPASS
Luís Silva; for the COMPASS Collaboration
2011-11-02T23:59:59.000Z
One of the missing keys in the present understanding of the spin structure of the nucleon is the contribution from the gluons: the so-called gluon polarisation. This quantity can be determined in DIS through the photon-gluon fusion process, in which two analysis methods may be used: (i) identifying open charm events or (ii) selecting events with high p_T hadrons. The data used in the present work were collected in the COMPASS experiment, where a 160 GeV/c naturally polarised muon beam, impinging on a polarised nucleon fixed target is used. Preliminary results for the gluon polarisation from high p_T and open charm analyses are presented. The gluon polarisation result for high p_T hadrons is divided, for the first time, into three statistically independent measurements at LO. The result from open charm analysis is obtained at LO and NLO. In both analyses a new weighted method based on a neural network approach is used.
Predictions for the Spatial Distribution of Gluons in the Initial Nuclear State
G. S. Jackson; W. A. Horowitz
2014-04-18T23:59:59.000Z
We make predictions for the t-differential cross section of exclusive vector meson production (EVMP) in electron-ion collisions, with the aim of comparing DGLAP evolution to CGC models. In the current picture for the high-energy nucleus, nonlinear effects need to be understood in terms of low-$x$ gluon radiation and recombination as well as how this leads to saturation. EVMP grants experimental access to the edge region of the highly-boosted nuclear wavefunction, where the saturation scale for CGC calculations becomes inaccessible to pQCD. On the other hand, DGLAP evolution requires careful consideration of unitarity effects. The existing $J/{\\psi}$ photoproduction data in ep collisions provides a baseline for these theoretical calculations. Under different small-$x$ frameworks we obtain a measurable distinction in both the shape and normalization of the differential cross section predictions. These considerations are relevant for heavy ion collisions because the initial state may be further constrained, thus aiding in quantitative study of the quark-gluon plasma.
The effect of partonic wind on charm quark correlations in high-energy nuclear collisions
X. Zhu; N. Xu; P. Zhuang
2007-09-03T23:59:59.000Z
In high-energy collisions, massive heavy quarks are produced back-to-back initially and they are sensitive to early dynamical conditions. The strong collective partonic wind from the fast expanding quark-gluon plasma created in high-energy nuclear collisions modifies the correlation pattern significantly. As a result, the angular correlation function for D$\\bar{\\rm D}$ pairs is suppressed at the angle $\\Delta\\phi=\\pi$. While the hot and dense medium in collisions at RHIC ($\\sqrt{s_{NN}}=200$ GeV) can only smear the initial back-to-back D$\\bar {\\rm D}$ correlation, a clear and strong near side D$\\bar{\\rm D}$ correlation is expected at LHC ($\\sqrt{s_{NN}}=5500$ GeV).
Angular Ordering in Gluon Radiation
Jong B. Choi; Byeong S. Choi; Su K. Lee
2002-01-28T23:59:59.000Z
The assumption of angular ordering in gluon radiation is essential to obtain quantitative results concerning gluonic behaviors. In order to prove the validity of this assumption, we have applied our momentum space flux-tube formalism to check out the angular dependences of gluon radiation. We have calculated the probability amplitudes to get new gluon, and have found that the new gluon is generally expected to have the maximum amplitude when it is produced between the momentum directions of the last two partons.
Heavy quark scattering and quenching in a QCD medium at finite temperature and chemical potential
Berrehrah, H; Cassing, W; Gossiaux, P B; Aichelin, J
2015-01-01T23:59:59.000Z
The heavy quark collisional scattering on partons of the quark gluon plasma (QGP) is studied in a QCD medium at finite temperature and chemical potential. We evaluate the effects of finite parton masses and widths, finite temperature $T$ and quark chemical potential $\\mu_q$ on the different elastic cross sections for dynamical quasi-particles (on- and off-shell particles in the QGP medium as described by the dynamical quasi-particles model "DQPM") using the leading order Born diagrams. Our results show clearly the decrease of the $qQ$ and $gQ$ total elastic cross sections when the temperature and the quark chemical potential increase. These effects are amplified for finite $\\mu_q$ at temperatures lower than the corresponding critical temperature $T_c (\\mu_q)$. Using these cross sections we, furthermore, estimate the energy loss and longitudinal and transverse momentum transfers of a heavy quark propagating in a finite temperature and chemical potential medium. Accordingly, we have shown that the transport pro...
Jorge Noronha; Miklos Gyulassy; Giorgio Torrieri
2009-03-16T23:59:59.000Z
We show that far zone Mach and diffusion wake ``holograms'' produced by supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict $N_c\\to\\infty$ supergravity limit if Cooper-Frye hadronization is assumed. However, a special {\\em nonequilibrium} ``neck'' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly-coupled Quark-Gluon Plasma (sQGP) implied by AdS/CFT correspondence.
Tensor gluons and proton structure
George Savvidy
2014-12-14T23:59:59.000Z
In a recent article we were considering a possibility that inside a proton and, more generally, inside hadrons there could be additional partons - tensor-gluons, which carry a part of the proton momentum. Tensor-gluons have zero electric charge, like gluons, but have a larger spin. Therefore we call them tensor-gluons. The nonzero density of tensor-gluons can be generated by the emission of tensor-gluons by gluons. Tensor-gluons can further split into the pairs of tensor-gluons through a different channels. To describe all these processes one should know the general splitting probabilities for tensor-gluons. These probabilities should fulfill very general symmetry relations, which we were able to resolve by introducing a splitting index. This approach allows to find out the general form of the splitting functions, to derive corresponding DGLAP evolution equations and to calculate the one-loop Callan-Simanzik beta function for tensor-gluons of a given spin. Our results provide a nontrivial consistency check of the theory and of the Callan-Simanzik beta function calculations, because the theory has a unique coupling constant and its high energy behavior should be universal for all particles of the spectrum. We argue that the contribution of all spins into the beta function vanishes leading to a conformal invariant theory at very high energies.
Ayala, A.L. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica][Pelotas Univ., RS (Brazil). Inst. de Fisica e Matematica; Ducati, M.B.G. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica; Levin, E.M. [Fermi National Accelerator Lab., Batavia, IL (United States)][Nuclear Physics Inst., St. Petersburg (Russian Federation)
1996-10-01T23:59:59.000Z
In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.
Static quark free energies at finite temperature with two flavors of improved Wilson quarks
Y. Maezawa; S. Ejiri; T. Hatsuda; N. Ishii; N. Ukita; S. Aoki; K. Kanaya
2006-10-02T23:59:59.000Z
Polyakov loop correlations at finite temperature in two-flavor QCD are studied in lattice simulations with the RG-improved gluon action and the clover-improved Wilson quark action. From the simulations on a $16^3 \\times 4$ lattice, we extract the free energies, the effective running coupling $g_{\\rm eff}(T)$ and the Debye screening mass $m_D(T)$ for various color channels of heavy quark--quark and quark--anti-quark pairs above the critical temperature. The free energies are well approximated by the screened Coulomb form with the appropriate Casimir factors. The magnitude and the temperature dependence of the Debye mass are compared to those of the next-to-leading order thermal perturbation theory and to a phenomenological formula given in terms of $g_{\\rm eff}(T)$. Also we made a comparison between our results with the Wilson quark and those with the staggered quark previously reported.
Single top quark production and Vtb at the Tevatron
Schwienhorst, Reinhard; /Michigan State U.
2010-09-01T23:59:59.000Z
Single top quark production via the electroweak interaction was observed by the D0 and CDF collaborations at the Tevatron proton-antiproton collider at Fermilab. Multivariate analysis techniques are employed to extract the small single top quark signal. The combined Tevatron cross section is 2.76{sub -0.47}{sup +0.58} pb. This corresponds to a lower limit on the CKM matrix element |V{sub tb}| of 0.77. Also reported are measurements of the t-channel cross section, the top quark polarization in single top quark events, and limits on gluon-quark flavor-changing neutral currents and W{prime} boson production.
Hadron structure with light dynamical quarks
LHPC Collaboration; Robert G. Edwards; George Taminga Fleming; Philipp Hagler; John W. Negele; Kostas Orginos; Andrew V. Pochinsky; Dru B. Renner; David G. Richards; Wolfram Schroers
2005-09-30T23:59:59.000Z
Generalized parton distributions encompass a wealth of information concerning the three-dimensional quark and gluon structure of the nucleon, and thus provide an ideal focus for the study of hadron structure using lattice QCD. The special limits corresponding to form factors and parton distributions are well explored experimentally, providing clear tests of lattice calculations, and the lack of experimental data for more general cases provides opportunities for genuine predictions and for guiding experiment. We present results from hybrid calculations with improved staggered (Asqtad) sea quarks and domain wall valence quarks at pion masses down to 350 MeV.
On the process-dependence of coherent medium-induced gluon radiation
Stéphane Peigné; Rodion Kolevatov
2014-05-16T23:59:59.000Z
Considering forward dijet production in the $q\\to qg$ partonic process, we derive the spectrum of accompanying soft gluon radiation induced by rescatterings in a nuclear target. The spectrum is obtained to logarithmic accuracy for an arbitrary energy sharing between the final quark and gluon, and for final transverse momenta as well as momentum imbalance being large as compared to transverse momentum nuclear broadening. In the case of equal energy sharing and for approximately back-to-back quark and gluon transverse momenta, we reproduce a previous result of Liou and Mueller. Interpreting our result, we conjecture a simple formula for the medium-induced radiation spectrum associated to hard forward $1 \\to n$ processes, which we explicitly check in the case of the $g \\to gg$ process.
Bound States of (Anti-)Scalar-Quarks in SU(3)c Lattice QCD
Iida, H.; Takahashi, T. T. [Yukawa Institute for Theoretical Physics, Kyoto University, Sakyo, Kyoto 606-8502 (Japan); Suganuma, H. [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)
2007-06-13T23:59:59.000Z
Light scalar-quarks {phi} (colored scalar particles or idealized diquarks) and their color-singlet hadronic states are studied with quenched SU(3)c lattice QCD in terms of mass generation. We investigate 'scalar-quark mesons' {phi}{dagger}{phi} and 'scalar-quark baryons' {phi}{phi}{phi} as the bound states of scalar-quarks {phi}. We also investigate the bound states of scalar-quarks {phi} and quarks {psi}, i.e., {phi}{dagger}{psi}, {psi}{psi}{phi} and {phi}{phi}{psi}, which we name 'chimera hadrons'. All the new-type hadrons including {phi} are found to have a large mass due to large quantum corrections by gluons, even for zero bare scalar-quark mass m{phi} = 0 at a-1 {approx} 1GeV. We conjecture that all colored particles generally acquire a large effective mass due to dressed gluon effects.
Particle multiplicity of unbiased gluon jets from $e^+ e^-$ three-jet events
Abbiendi, G; Åkesson, P F; Alexander, Gideon; Allison, J; Anagnostou, G; Anderson, K J; Arcelli, S; Asai, S; Axen, D A; Azuelos, Georges; Bailey, I; Barberio, E; Barlow, R J; Batley, J Richard; Bechtle, P; Behnke, T; Bell, K W; Bell, P J; Bella, G; Bellerive, A; Benelli, G; Bethke, Siegfried; Biebel, O; Bloodworth, Ian J; Boeriu, O; Bock, P; Böhme, J; Bonacorsi, D; Boutemeur, M; Braibant, S; Brigliadori, L; Brown, R M; Burckhart, H J; Cammin, J; Campana, S; Carnegie, R K; Caron, B; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Clarke, P E L; Clay, E; Cohen, I; Couchman, J; Csilling, Akos; Cuffiani, M; Dado, S; Dallavalle, G M; Dallison, S; de Roeck, A; De Wolf, E A; Dervan, P J; Desch, Klaus; Dienes, B; Donkers, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Etzion, E; Fabbri, Franco Luigi; Feld, L; Ferrari, P; Fiedler, F; Fleck, I; Ford, M; Frey, A; Fürtjes, A; Futyan, D I; Gagnon, P; Gary, J W; Gaycken, G; Geich-Gimbel, C; Giacomelli, G; Giacomelli, P; Giunta, M; Goldberg, J; Graham, K; Gross, E; Grunhaus, Jacob; Gruwé, M; Günther, P O; Sen-Gupta, A; Hajdu, C; Hamann, M; Hanson, G G; Harder, K; Harel, A; Harin-Dirac, M; Hauschild, M; Hauschildt, J; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Hensel, C; Herten, G; Heuer, R D; Hill, J C; Hoffman, K; Homer, R James; Horváth, D; Hossain, K R; Howard, R; Hüntemeyer, P; Igo-Kemenes, P; Ishii, K; Jawahery, A; Jeremie, H; Jones, C R; Jovanovic, P; Junk, T R; Kanaya, N; Kanzaki, J; Karapetian, G V; Karlen, D A; Kartvelishvili, V G; Kawagoe, K; Kawamoto, T; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Kim, D H; Klein, K; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Kokott, T P; Komamiya, S; Kowalewski, R V; Kramer, T; Kress, T; Krieger, P; Von Krogh, J; Krop, D; Kühl, T; Kupper, M; Kyberd, P; Lafferty, G D; Landsman, Hagar Yaël; Lanske, D; Lawson, I; Layter, J G; Leins, A; Lellouch, Daniel; Letts, J; Levinson, L; Lillich, J; Littlewood, C; Lloyd, S L; Loebinger, F K; Lü, J; Ludwig, J; Macchiolo, A; MacPherson, A L; Mader, W; Marcellini, S; Marchant, T E; Martin, A J; Martin, J P; Martínez, G; Masetti, G; Mashimo, T; Mättig, P; McDonald, W J; McKenna, J A; McMahon, T J; McPherson, R A; Meijers, F; Méndez-Lorenzo, P; Menges, W; Merritt, F S; Mes, H; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Moed, S; Mohr, W; Mori, T; Mutter, A; Nagai, K; Nakamura, I; Neal, H A; Nisius, R; O'Neale, S W; Oh, A; Okpara, A N; Oreglia, M J; Orito, S; Pahl, C; Pásztor, G; Pater, J R; Patrick, G N; Pilcher, J E; Pinfold, James L; Plane, D E; Poli, B; Polok, J; Pooth, O; Quadt, A; Rabbertz, K; Rembser, C; Renkel, P; Rick, Hartmut; Rodning, N L; Roney, J M; Rosati, S; Roscoe, K; Rozen, Y; Runge, K; Rust, D R; Sachs, K; Saeki, T; Sahr, O; Sarkisyan-Grinbaum, E; Schaile, A D; Schaile, O; Scharff-Hansen, P; Schröder, M; Schumacher, M; Schwick, C; Scott, W G; Seuster, R; Shears, T G; Shen, B C; Shepherd-Themistocleous, C H; Sherwood, P; Skuja, A; Smith, A M; Snow, G A; Sobie, Randall J; Söldner-Rembold, S; Spagnolo, S; Spanó, F; Sproston, M; Stahl, A; Stephens, K; Strom, D; Ströhmer, R; Stumpf, L; Surrow, B; Tarem, S; Tasevsky, M; Taylor, R J; Teuscher, R; Thomas, J; Thomson, M A; Torrence, E; Toya, D; Trefzger, T M; Tricoli, A; Trigger, I; Trócsányi, Z L; Tsur, E; Turner-Watson, M F; Ueda, I; Ujvári, B; Vachon, B; Vollmer, C F; Vannerem, P; Verzocchi, M; Voss, H; Vossebeld, Joost Herman; Waller, D; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wengler, T; Wermes, N; Wetterling, D; Wilson, G W; Wilson, J A; Wyatt, T R; Yamashita, S; Zacek, V; Zer-Zion, D; 10.1007/s100520200926
2002-01-01T23:59:59.000Z
The charged particle multiplicities of two- and three-jet events from the reaction e+e- -> Z0 -> hadrons are measured for Z0 decays to light quark (uds) flavors. Using recent theoretical expressions to account for biases from event selection, results corresponding to unbiased gluon jets are extracted over a range of jet energies from about 11 to 30 GeV. We find consistency between these results and direct measurements of unbiased gluon jet multiplicity from upsilon and Z0 decays. The unbiased gluon jet data including the direct measurements are compared to corresponding results for quark jets. We perform fits based on analytic expressions for particle multiplicity in jets to determine the ratio r = Ng/Nq of multiplicities between gluon and quark jets as a function of energy. We also determine the ratio of slopes, r(1) = (dNg/dy)/(dNq/dy), and of curvatures, r(2) = (d2Ng/dy2)/(d2Nq/dy2), where y specifies the energy scale. At 30 GeV, we find r = 1.422 +/- 0.051, r(1) = 1.761 +/- 0.071 and r(2) = 1.98 +/- 0.13,...
Transverse quark distribution in mesons: QCD sum rule approach
Lee, S.H.; Hatsuda, T.; Miller, G.A. (Department of Physics, FM-15, University of Washingtion, Seattle, Washington 98195 (United States) Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of))
1994-04-11T23:59:59.000Z
QCD sum rules are used to compute the first few moments of the mesonic quark momentum. Transverse, longitudinal, and mixed transverse-longitudinal components are examined. The transverse size of the pion is shown to be dictated by the gluon condensate, even though the mass and the longitudinal distribution are dominated by the quark condensate. The implications of our results for color transparency physics and finite temperature QCD are discussed.
Friction Coefficient for Quarks in Supergravity Duals
E. Antonyan
2006-11-22T23:59:59.000Z
We study quarks moving in strongly-coupled plasmas that have supergravity duals. We compute the friction coefficient of strings dual to such quarks for general static supergravity backgrounds near the horizon. Our results also show that a previous conjecture on the bound has to be modified and higher friction coefficients can be achieved.
Scalar Higgs boson production in a fusion of two off-shell gluons
R. S. Pasechnik; O. V. Teryaev; A. Szczurek
2006-03-30T23:59:59.000Z
The amplitude for scalar Higgs boson production in a fusion of two off-shell gluons is calculated including finite (not infinite) masses of quarks in the triangle loop. In comparison to the effective Lagrangian approach, we have found a new term in the amplitude. The matrix element found can be used in the kt-factorization approach to the Higgs boson production. The results are compared with the calculations for on-shell gluons. Small deviations from the cos(phi)^2-dependence are predicted. The off-shell effects found are practically negligible.
N. Cardoso; M. Cardoso; P. Bicudo
2012-11-19T23:59:59.000Z
The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a $24^3\\times 48$ lattice at $\\beta=6.2$ and $a=0.07261(85)\\,fm$. We compute the hybrid Wilson Loop including the cases when the gluon and the antiquark are superposed, i. e., the quark-antiquark case and when the quark and antiquark are superposed, i. e., the gluon-gluon case. The Casimir scaling is investigated, in the two gluon glueball case the Casimir scaling is consistent with the formation of an adjoint string. Measuring the decay of the tail in the mid section of the flux tube for the two gluon glueball and for the quark-antiquark meson, we determine the penetration length and present a gauge invariant effective dual gluon mass of $0.905\\pm0.163\\,\\text{GeV}$. We also try to determine the coherence length comparing our results with the dual Ginzburg-Landau approach. With the penetration length and the possible coherence length we determine a putative Ginzburg-Landau dimensionless parameter, which is possibly consistent with a type II superconductor picture. These results are obtained at fixed quark-antiquark distance of 0.58 fm.
Local Gauge Transformation for the Quark Propagator in an SU(N) Gauge Theory
Aslam, M Jamil; Gutierrez-Guerrero, L X
2015-01-01T23:59:59.000Z
In an SU(N) gauge field theory, the n-point Green functions, namely, propagators and vertices, transform under the simultaneous local gauge variations of the gluon vector potential and the quark matter field in such a manner that the physical observables remain invariant. In this article, we derive this intrinsically non perturbative transformation law for the quark propagator within the system of covariant gauges. We carry out its explicit perturbative expansion till O(g_s^6) and, for some terms, till O(g_s^8). We study the implications of this transformation for the quark-anti-quark condensate, multiplicative renormalizability of the massless quark propagator, as well as its relation with the quark-gluon vertex at the one-loop order. Setting the color factors C_F=1 and C_A=0, Landau-Khalatnikov-Fradkin transformation for the abelian case of quantum electrodynamics is trivially recovered.
Vol. 48 No. SIG 0(PRO 35) 2007 Java Remote GluonJ Remote GluonJ
Chiba, Shigeru
Vol. 48 No. SIG 0(PRO 35) 2007 Java Remote GluonJ Remote GluonJ Remote GluonJ Remote GluonJ Java Remote GluonJ Remote GluonJ An AOP based Agile Development Environment for Distributed Software Muga/from the existing program easily. To support software development for Java with our method, we developed Remote
Improving the Top Quark Forward-Backward Asymmetry Measurement at the LHC
Bai, Yang; /SLAC; Han, Zhenyu; /Harvard U., Phys. Dept.
2011-08-15T23:59:59.000Z
At the LHC, top quark pairs are dominantly produced from gluons, making it difficult to measure the top quark forward-backward asymmetry. To improve the asymmetry measurement, we study variables that can distinguish between top quarks produced from quarks and those from gluons: the invariant mass of the top pair, the rapidity of the top-antitop system in the lab frame, the rapidity of the top quark in the top-antitop rest frame, the top quark polarization and the top-antitop spin correlation. We combine all the variables in a likelihood discriminant method to separate quark-initiated events from gluon-initiated events. We apply our method on models including G-prime's and W-prime's motivated by the recent observation of a large top quark forward-backward asymmetry at the Tevatron. We have found that the significance of the asymmetry measurement can be improved by 10% to 30%. At the same time, the central values of the asymmetry increase by 40% to 100%. We have also analytically derived the best spin quantization axes for studying top quark polarization as well as spin-correlation for the new physics models.
Parton energy loss and momentum broadening at NLO in high temperature QCD plasmas
Ghiglieri, Jacopo
2015-01-01T23:59:59.000Z
We present an overview of a perturbative-kinetic approach to jet propagation, energy loss, and momentum broadening in a high temperature quark-gluon plasma. The leading-order kinetic equations describe the interactions between energetic jet-particles and a non-abelian plasma, consisting of on-shell thermal excitations and soft gluonic fields. These interactions include 22 scatterings, collinear bremsstrahlung, and drag and momentum diffusion. We show how the contribution from the soft gluonic fields can be factorized into a set of Wilson line correlators on the light cone. We review recent field-theoretical developments, rooted in the causal properties of these correlators, which simplify the calculation of the appropriate Wilson lines in thermal field theory. With these simplifications lattice measurements of transverse momentum broadening have become possible, and the kinetic equations describing parton transport have been extended to next-to-leading order in the coupling g.
Heavy quarks in deeply virtual Compton scattering
Jens D. Noritzsch
2003-12-11T23:59:59.000Z
A detailed study of the heavy quark h=c,b,... contributions to deeply virtual Compton scattering is performed at both the amplitude and the cross section level, and their phenomenological relevance is discussed. For this purpose I calculate the lowest order off-forward photon-gluon scattering amplitude with a massive quark loop and the corresponding hard scattering coefficients. In a first numerical analysis these fixed order perturbation theory results are compared with the conventional intrinsic "massless" parton approach considering generalized parton distributions for the heavy quarks. The differences between these two prescriptions can be quite significant, especially at small skewedness where the massless approach largely overestimates the deeply virtual Compton scattering cross section.
Gluon self-energy in the color-flavor-locked phase
Malekzadeh, H; Rischke, Dirk H.
2006-01-01T23:59:59.000Z
We calculate the self-energies and the spectral densities of longitudinal and transverse gluons at zero temperature in color-superconducting quark matter in the color-flavor-locked (CFL) phase. We find a collective excitation, a plasmon, at energies smaller than two times the gap parameter and momenta smaller than about eight times the gap. The dispersion relation of this mode exhibits a minimum at some nonzero value of momentum, indicating a van Hove singularity.
Gluon self-energy in the color-flavor-locked phase
H. Malekzadeh; Dirk H. Rischke
2006-06-08T23:59:59.000Z
We calculate the self-energies and the spectral densities of longitudinal and transverse gluons at zero temperature in color-superconducting quark matter in the color-flavor-locked (CFL) phase. We find a collective excitation, a plasmon, at energies smaller than two times the gap parameter and momenta smaller than about eight times the gap. The dispersion relation of this mode exhibits a minimum at some nonzero value of momentum, indicating a van Hove singularity.
On Multiple Gluon Exchange Webs
Mark Harley
2015-05-21T23:59:59.000Z
I present an overview of the study of infrared singularities through the eikonal approximation and the concept of webs. Our work reveals the interesting structure of an infinite subclass of webs, Multiple Gluon Exchange Webs. We find that they can be expressed as sums of products of functions depending upon only a single cusp angle, spanned by a simple basis of functions, and conjecture that this structure will hold to all orders.
Simon Caron-Huot
2015-05-19T23:59:59.000Z
We propose the eikonal approximation as a simple and reliable tool to analyze relativistic high-energy processes, provided that the necessary subtleties are accounted for. An important subtlety is the need to include eikonal phases for a rapidity-dependent collection of particles, as embodied by the Balitsky-JIMWLK rapidity evolution equation. In the first part of this paper, we review how the phenomenon of gluon reggeization and the BFKL equations can be understood simply (but not too simply) in the eikonal approach. We also work out some previously overlooked implications of BFKL dynamics, including the observation that starting from four loops it is incompatible with a recent conjecture regarding the structure of infrared divergences. In the second part of this paper, we propose that in the strict planar limit the theory can be developed to all orders in the coupling with no reference at all to the concept of "reggeized gluon." Rather, one can work directly with a finite, process-dependent, number of Wilson lines. We demonstrate consistency of this proposal by an exact computation in N=4 super Yang-Mills, which shows that in processes mediated with two Wilson lines the reggeized gluon appears in the weak coupling limit as a resonance whose width is proportional to the coupling. We also provide a precise operator definition of Lipatov's integrable spin chain, which is manifestly integrable at any value of the coupling as a result of the duality between scattering amplitudes and Wilson loops in this theory.
Horava–Lifshitz cosmology, entropic interpretation and quark–hadron phase transition
Kheyri, F., E-mail: F_Kheyri@sbu.ac.ir; Khodadi, M., E-mail: M.Khodadi@sbu.ac.ir; Sepangi, Hamid Reza, E-mail: hr-sepangi@sbu.ac.ir
2013-05-15T23:59:59.000Z
Based on the assumptions of the standard model of cosmology, a phase transition associated with chiral symmetry breaking after the electroweak transition has occurred at approximately 10 ?s after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider such a phase transition in the context of a deformed Horava–Lifshitz cosmology. The Friedmann equation for the deformed Horava–Lifshitz universe is obtained using the entropic interpretation of gravity, proposed by Verlinde. We investigate the effects of the parameter ? appearing in the theory on the evolution of the physical quantities relevant to a description of the early universe, namely, the energy density and temperature before, during and after the phase transition. Finally, we study the cross-over phase transition in both high and low temperature regions in view of the recent lattice QCD simulations data. -- Highlights: ? We study the problem of the quark–hadron phase transition in the early universe, in the context of Horava–Lifshitz cosmology. ? We conduct this study by including the recently introduced entropic principle. ? We study the behavior of thermodynamical parameters of the theory.
Gluon Fusion Processes at One-loop within the Standard Model and Beyond
Ambresh Shivaji
2013-05-21T23:59:59.000Z
In this thesis, we have studied certain gluon fusion processes which proceed via quark loop diagrams at the leading order. The fact that these gluon-gluon channel processes are independent processes, their contributions towards the total/differential hadronic cross sections can be calculated separately. We have considered the production of a pair of electroweak vector bosons in association with a jet via gluon fusion within the standard model. These processes were not accessible at earlier hadron colliders such as the Tevatron. Therefore, observation of these rare processes at the LHC will be a test of the standard model itself. Like the di-vector boson production via gluon fusion processes, these processes are also important backgrounds for many new physics signals, and the standard model Higgs boson signal at the LHC. These leading order gluon fusion processes contribute to the corresponding hadronic processes at the next-to-next-to-leading order in {\\alpha}_s. We have taken a model of extra-dimensions, the ADD (Arkani-Hamed, Dimopoulos and Dvali) model, as the possible candidate of new physics at the LHC. This model tries to solve the hierarchy problem of the standard model by proposing large extra space dimensions which may be accessible at TeV scale. We have considered the direct production of KK-gravitons (GKK) in association with an electroweak boson (H/{\\gamma}/Z) via gluon fusion. These processes contribute to the corresponding hadronic processes at the next-to-leading order in {\\alpha}_s. Many interesting issues related to the fermion loop amplitudes have also been discussed.
Recent PQCD calculations of heavy quark production
Vitev, I
2006-01-01T23:59:59.000Z
We summarize the results of a recent study of heavy quark production and attenuation in cold nuclear matter. In p+p collisions, we investigate the relative contribution of partonic sub-processes to $D$ meson production and $D$ meson-triggered inclusive di-hadrons to lowest order in perturbative QCD. While gluon fusion dominates the creation of large angle $D\\bar{D}$ pairs, charm on light parton scattering determines the yield of single inclusive $D$ mesons. The distinctly different non-perturbative fragmentation of $c$ quarks into $D$ mesons versus the fragmentation of quarks and gluons into light hadrons results in a strong transverse momentum dependence of anticharm content of the away-side charm-triggered jet. In p+A reactions, we calculate and resum the coherent nuclear-enhanced power corrections from the final-state partonic scattering in the medium. We find that single and double inclusive open charm production can be suppressed as much as the yield of neutral pions from dynamical high-twist shadowing. ...
Measurement of the gluon polarisation at COMPASS
G. Brona; for the COMPASS Collaboration
2007-05-16T23:59:59.000Z
COMPASS experiment measurements of the gluon polarisation in nucleon, DeltaG/G are reviewed. Two different approaches based on tagging the Photon Gluon Fusion process are described. They rely on the open charm meson or high-p_T hadron pairs detection.
Abrikosov Gluon Vortices in Color Superconductors
Efrain J. Ferrer
2010-04-05T23:59:59.000Z
In this talk I will discuss how the in-medium magnetic field can influence the gluon dynamics in a three-flavor color superconductor. It will be shown how at field strengths comparable to the charged gluon Meissner mass a new phase can be realized, giving rise to Abrikosov's vortices of charged gluons. In that phase, the inhomogeneous gluon condensate anti-screens the magnetic field due to the anomalous magnetic moment of these spin-1 particles. This paramagnetic effect can be of interest for astrophysics, since due to the gluon vortex antiscreening mechanism, compact stars with color superconducting cores could have larger magnetic fields than neutron stars made up entirely of nuclear matter. I will also discuss a second gluon condensation phenomenon connected to the Meissner instability attained at moderate densities by two-flavor color superconductors. In this situation, an inhomogeneous condensate of charged gluons emerges to remove the chromomagnetic instability created by the pairing mismatch, and as a consequence, the charged gluonic currents induce a magnetic field. Finally, I will point out a possible relation between glitches in neutron stars and the existence of the gluon vortices.
Scalar-Quark Systems and Chimera Hadrons in SU(3)_c Lattice QCD
H. Iida; H. Suganuma; T. T. Takahashi
2007-05-28T23:59:59.000Z
Light scalar-quarks \\phi (colored scalar particles or idealized diquarks) and their color-singlet hadronic states are studied with quenched SU(3)_c lattice QCD in terms of mass generation in strong interaction without chiral symmetry breaking. We investigate ``scalar-quark mesons'' \\phi^\\dagger \\phi and ``scalar-quark baryons'' \\phi\\phi\\phi which are the bound states of scalar-quarks \\phi. We also investigate the bound states of scalar-quarks \\phi and quarks \\psi, i.e., \\phi^\\dagger \\psi, \\psi\\psi\\phi and \\phi\\phi\\psi, which we name ``chimera hadrons''. All the new-type hadrons including \\phi are found to have a large mass even for zero bare scalar-quark mass m_\\phi=0 at a^{-1}\\simeq 1GeV. We find that the constituent scalar-quark and quark picture is satisfied for all the new-type hadrons. Namely, the mass of the new-type hadron composed of m \\phi's and n \\psi's, M_{{m}\\phi+{n}\\psi}, satisfies M_{{m}\\phi+{n}\\psi}\\simeq {m} M_\\phi +{n} M_\\psi, where M_\\phi and M_\\psi are the constituent scalar-quark and quark mass, respectively. M_\\phi at m_\\phi=0 estimated from these new-type hadrons is 1.5-1.6GeV, which is larger than that of light quarks, M_\\psi\\simeq 400{\\rm MeV}. Therefore, in the systems of scalar-quark hadrons and chimera hadrons, scalar-quarks acquire large mass due to large quantum corrections by gluons. Together with other evidences of mass generations of glueballs and charmonia, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluon effects.
Soft gluons are heavy and rowdy
Reinhard Alkofer; Pedro Bicudo; Stephen R. Cotanch; Christian S. Fischer; Felipe J. Llanes-Estrada
2006-01-10T23:59:59.000Z
We study dynamical mass generation in pure Yang-Mills theory and report on a recently developed ansatz that exactly solves the tower of Dyson-Schwinger equations in Landau gauge at low Euclidean momentum, featuring enhanced gluon-gluon vertices, a finite ghost-gluon vertex in agreement with an old argument of Taylor, and an IR suppressed gluon propagator. This ansatz reinforces arguments in favor of the concept of a gluon mass gap at low momentum (although the minimum of the gluon's dispersion relation is not at zero momentum). As an application, we have computed the spectrum of oddballs, three-gluon glueballs with negative parity and C-parity. The three body problem is variationally solved employing the color density-density interaction of Coulomb gauge QCD with a static Cornell potential. Like their even glueball counterparts, oddballs fall on Regge trajectories with similar slope to the pomeron. However their intercept at t=0 is smaller than the omega Regge trajectory and therefore the odderon may only be visible in experimental searches (for example at BNL) with higher -t than conducted to date at DESY.
Coulomb-gauge ghost and gluon propagators in SU(3) lattice Yang-Mills theory
Nakagawa, Y.; Toki, H. [Research Center for Nuclear Physics, Osaka University, Ibaraki-shi, Osaka 567-0047 (Japan); Voigt, A. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, D-12489 Berlin (Germany); Max-Planck-Institut fuer Meteorologie, D-20146 Hamburg (Germany); Ilgenfritz, E.-M. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, D-12489 Berlin (Germany); Karl-Franzens-Universitaet Graz, Institut fuer Physik, A-8010 Graz (Austria); Mueller-Preussker, M. [Humboldt-Universitaet zu Berlin, Institut fuer Physik, D-12489 Berlin (Germany); Nakamura, A. [Research Institute for Information Science and Education, Hiroshima University, Higashi-Hiroshima 739-8521 (Japan); Saito, T. [Integrated Information Center, Kochi University, Akebono-cho, Kochi 780-8520 (Japan); Sternbeck, A. [CSSM, School of Chemistry and Physics, University of Adelaide, SA 5005 (Australia)
2009-06-01T23:59:59.000Z
We study the momentum dependence of the ghost propagator and of the space and time components of the gluon propagator at equal time in pure SU(3) lattice Coulomb-gauge theory carrying out a joint analysis of data collected independently at the Research Center for Nuclear Physics, Osaka and Humboldt University, Berlin. We focus on the scaling behavior of these propagators at {beta}=5.8,...,6.2 and apply a matching technique to relate the data for the different lattice cutoffs. Thereby, lattice artifacts are found to be rather strong for both instantaneous gluon propagators at a large momentum. As a byproduct we obtain the respective lattice scale dependences a({beta}) for the transversal gluon and the ghost propagator which indeed run faster with {beta} than two-loop running, but slightly slower than what is known from the Necco-Sommer analysis of the heavy quark potential. The abnormal a({beta}) dependence as determined from the instantaneous time-time gluon propagator, D{sub 44}, remains a problem, though. The role of residual gauge-fixing influencing D{sub 44} is discussed.
Quark Coalescence at High Energies University of Alabama in Huntsville/
Lin, Zi-wei
: ZWL,Ko&Pal, PRL89(02) v4, v6, ...: Chen,Ko&ZWL, PRC69(04) Flavor ordering of v2 at high Pt: ZWL&Ko, PRL89(02) Amplification of quark v2 and ordering: Voloshin, NPA715(03); Molnar&Voloshin, PRL91 et al, PRL90(03); Greco,Ko&Levai, PRL90(03); ... #12;Near hadronization, gluons may decouple (serve
Gluon EMC effect and fractional energy loss in Upsilon production in dAu collisions at RHIC
Ferreiro, E G; Lansberg, J P; Matagne, N; Rakotozafindrabe, A
2011-01-01T23:59:59.000Z
We demonstrate that the nuclear modification factor R^Upsilon_dAu measured at RHIC can only be reproduced once two supplemental Cold Nuclear Matter effects are taken into account. At backward rapidities, the visible suppression of R^Upsilon_dAu hints at the presence of a gluon EMC effect, analogous to the quark EMC effect -- but likely stronger. At forward and mid rapidities, the data can only be accounted for by a fractional energy loss, recently revived in the literature. Our conclusions do not depend on the detail of the nuclear parton distributions. We thus argue that this may be the first observation of a gluon EMC effect stronger than the quark one.
Koepf, W. [School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Tel Aviv (Israel)] [School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Tel Aviv (Israel); Wilets, L. [Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States)] [Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States)
1995-06-01T23:59:59.000Z
We employ a relativistic quark bag picture, the chromodielectric soliton model, to discuss the quarks` symmetry structure and momentum distribution in the {ital N}-{ital N} system. Six-quark clusters are constructed in a constrained mean-field calculation. The corresponding Hamiltonian contains not only an effective interaction between the quarks and a scalar field, which is assumed to parametrize all nonperturbative effects due to the nonlinearity of QCD, but also quark-quark interactions mediated through one-gluon exchange. We also evaluate the quark light-cone distribution functions, characterizing inclusive deep-inelastic lepton scattering, for the nucleon as well as for the six-quark structures. We find a competition between a softening of the quarks` momenta through the increase of the confinement volume, and a hardening via the admixture of higher symmetry configurations due to the color-electrostatic one-gluon exchange. These findings suggest an unexpected absence of many-nucleon, multiquark effects, even though six-quark structures should represent a nonnegligible part of the nuclear ground state.
B. L. Ioffe
2009-06-01T23:59:59.000Z
It is demonstrated, that chirality violating condensates in massless QCD arise from zero mode solutions of Dirac equations in arbitrary gluon fields. Basing of this idea, the model is suggested, which allows one to calculate quark condensate magnetic susceptibilities in the external constant electromagnetic field.
Charm and Beauty in a Hot Environment
Helmut Satz
2006-02-28T23:59:59.000Z
We discuss the spectral analysis of quarkonium states in a hot medium of deconfined quarks and gluons, and we show that such an analysis provides a way to determine the thermal properties of the quark-gluon plasma.
Basic features of the pion valence-quark distribution function
Lei Chang; Cédric Mezrag; Hervé Moutarde; Craig D. Roberts; Jose Rodríguez-Quintero; Peter C. Tandy
2014-06-20T23:59:59.000Z
The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow-ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables a realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, $q^\\pi(x)$; namely, at a characteristic hadronic scale, $q^\\pi(x) \\sim (1-x)^2$ for $x\\gtrsim 0.85$; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.
Yannis Burnier; Olaf Kaczmarek; Alexander Rothkopf
2014-11-12T23:59:59.000Z
We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method. We perform simulations on quenched $32^3\\times N_\\tau$ $(\\beta=7.0,\\xi=3.5)$ lattices with $N_\\tau=24,...,96$, which cover $839{\\rm MeV} \\geq T\\geq 210 {\\rm MeV}$. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize $N_f=2+1$ ASQTAD lattices with $m_l=m_s/20$ by the HotQCD collaboration, giving access to temperatures between $286 {\\rm MeV} \\geq T\\geq 148{\\rm MeV}$. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints.
The effects of colored quark entropy on the bag pressure
Miller, David E
2004-01-01T23:59:59.000Z
We study the effects of the ground state entropy of colored quarks upon the bag pressure at low temperatures. The vacuum expectation values of the quark and gluon fields are used to express the interactions in QCD ground state in the limit of low temperatures and chemical potentials. Apparently, the inclusion of this entropy in the equation of state provides the hadron constituents with an additional heat which causes a decrease in the effective latent heat inside the hadronic bag and consequently decreases the non-perturbative bag pressure. We have considered two types of baryonic bags, $\\Delta$ and $\\Omega^-$. In both cases we have found that the bag pressure decreases with the temperature. On the other hand, when the colored quark ground state entropy is not considered, the bag pressure as conventionally believed remains constant for finite temperature.
Higgs boson plus photon production at the LHC: a clean probe of the b-quark parton densities
Emidio Gabrielli; Barbara Mele; Johan Rathsman
2007-12-04T23:59:59.000Z
Higgs boson production in association with a high pT photon at the CERN Large Hadron Collider is analyzed, in the framework of the MSSM model, for the heavier neutral Higgs bosons. The request of an additional photon in the exclusive Higgs boson final state selects b-quark pairs among the possible initial partonic states, since gluon-gluon initial states are not allowed by C-parity conservation. Hence, the measurement of cross sections for neutral Higgs boson plus photon production can provide a clean probe of the b-quark density in the proton as well as of the b-quark Yukawa coupling. The suppression of the production rates by the b-quark electromagnetic coupling can be compensated by the enhanced Higgs boson Yukawa coupling to b's in the large tan(beta) regime. The Higgs boson decay into a tau-lepton pair is considered, and irreducible backgrounds with corresponding signal significances are evaluated.
Thermalization of gluon matter including ggggg interactions
A. El; C. Greiner; Z. Xu
2006-09-27T23:59:59.000Z
Within a pQCD inspired kinetic parton cascade we simulate the space time evolution of gluons which are produced initially in a heavy ion collision at RHIC energy. The inelastic gluonic interactions $gg \\leftrightarrow ggg$ do play an important role: For various initial conditions it is found that thermalization and the close to ideal fluid dynamical behaviour sets in at very early times. Special emphasis is put on color glass condensate initial conditions and the `bottom up thermalization' scenario. Off-equilibrium $3\\to 2$ processes make up the very beginning of the evolution leading to an initial decrease in gluon number and a temporary avalanche of the gluon momentum distribution to higher transversal momenta.
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; K. Kanaya; H. Ohno; T. Umeda
2009-11-02T23:59:59.000Z
The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature. We perform simulations on $32^3 \\times 12$, 10, 8, 6, 4 lattices in the high temperature phase with the RG-improved gluon action and 2+1 flavors of the clover-improved Wilson quark action. Since the simulations are based on the fixed scale approach that the temperature can be varied without changing the spatial volume and renormalization factor, it is possible to investigate temperature dependence of the heavy-quark free energy without any adjustment of the overall constant. We find that, the heavy-quark free energies at short distance converge to the heavy-quark potential evaluated from the Wilson-loop operator at zero temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the heavy-quark free energies approach to twice the single-quark free energies, implying that the interaction between heavy quarks is screened. The Debye screening mass obtained from the long range behavior of the heavy-quark free energy is compared with results of the thermal perturbation theory and those of $N_f=2$ and $N_f=0$ lattice simulations.
On the Equation of State of the Gluon Plasma
Zwanziger, Daniel [New York University, New York, NY 10003 (United States)
2007-02-27T23:59:59.000Z
We consider a local, renormalizable, BRST-invariant action for QCD in Coulomb gauge that contains auxiliary bose and fermi ghost fields. It possess a non-perturbative vacuum that spontaneously breaks BRST-invariance. The vacuum condition leads to a gap equation that introduces a mass scale. Calculations are done to one-loop order in a perturbative expansion about this vacuum. They are free of the finite-T infrared divergences found by Linde and which occur in the order g6 corrections to the Stefan-Boltzmann equation of state. We obtain a finite result for these corrections.
Shear Viscosity in a CFL Quark Star
Cristina Manuel; Antonio Dobado; Felipe J. Llanes-Estrada
2005-09-30T23:59:59.000Z
We compute the mean free path and shear viscosity in the color-flavor locked (CFL) phase of dense quark matter at low temperature T, when the contributions of mesons, quarks and gluons to the transport coefficients are Boltzmann suppressed. CFL quark matter displays superfluid properties, and transport phenomena in such cold regime are dominated by phonon-phonon scattering. We study superfluid phonons within thermal field theory and compute the mean free path associated to their most relevant collision processes. Small-angle processes turn out to be more efficient in slowing transport phenomena in the CFL matter, while the mean free path relevant for the shear viscosity is less sensitive to collinear scattering due to the presence of zero modes in the Boltzmann equation. In analogy with superfluid He4, we find the same T power law for the superfluid phonon damping rate and mean free path. Our results are relevant for the study of rotational properties of compact stars, and correct wrong estimates existing in the literature.
The Form Factors of the Gauge-Invariant Three-Gluon Vertex
Binger, Michael; Brodsky, Stanley J.
2006-02-24T23:59:59.000Z
The gauge-invariant three-gluon vertex obtained from the pinch technique is characterized by thirteen nonzero form factors, which are given in complete generality for unbroken gauge theory at one loop. The results are given in d dimensions using both dimensional regularization and dimensional reduction, including the effects of massless gluons and arbitrary representations of massive gauge bosons, fermions, and scalars. We find interesting relations between the functional forms of the contributions from gluons, quarks, and scalars. These relations hold only for the gauge-invariant pinch technique vertex and are d-dimensional incarnations of supersymmetric nonrenormalization theorems which include finite terms. The form factors are shown to simplify for N = 1, 2, and 4 supersymmetry in various dimensions. In four-dimensional non-supersymmetric theories, eight of the form factors have the same functional form for massless gluons, quarks, and scalars, when written in a physically motivated tensor basis. For QCD, these include the tree-level tensor structure which has prefactor {beta}{sub 0} = (11N{sub c}-2N{sub f})/3, another tensor with prefactor 4N{sub c} - N{sub f}, and six tensors with N{sub c} - N{sub f}. In perturbative calculations our results lead naturally to an effective coupling for the three-gluon vertex, {tilde {alpha}}(k{sub 1}{sup 2}, k{sub 2}{sup 2}, k{sub 3}{sup 2}), which depends on three momenta and gives rise to an effective scale Q{sub eff}{sup 2} (k{sub 1}{sup 2}, k{sub 2}{sup 2}, k{sub 3}{sup 2}) which governs the behavior of the vertex. The effects of nonzero internal masses M are important and have a complicated threshold and pseudo-threshold structure. A three-scale effective number of flavors N{sub F}(k{sub 1}{sup 2}/M{sup 2}, k{sub 2}{sup 2}/M{sup 2}, k{sub 3}{sup 2}/M{sup 2}) is defined. The results of this paper are an important part of a gauge-invariant dressed skeleton expansion and a related multi-scale analytic renormalization scheme. In this approach the scale ambiguity problem is resolved since physical kinematic invariants determine the arguments of the couplings.
Scalar-quark systems and chimera hadrons in SU(3){sub c} lattice QCD
Iida, H.; Takahashi, T. T. [Yukawa Institute for Theoretical Physics, Kyoto University, Sakyo, Kyoto 606-8502 (Japan); Suganuma, H. [Department of Physics, Kyoto University, Graduate School of Science, Sakyo, Kyoto 606-8502 (Japan)
2007-06-01T23:59:59.000Z
In terms of mass generation in the strong interaction without chiral symmetry breaking, we perform the first study for light scalar-quarks {phi} (colored scalar particles with 3{sub c} or idealized diquarks) and their color-singlet hadronic states using quenched SU(3){sub c} lattice QCD with {beta}=5.70 (i.e., a{approx_equal}0.18 fm) and lattice size 16{sup 3}x32. We investigate ''scalar-quark mesons'' {phi}{sup {dagger}}{phi} and ''scalar-quark baryons'' {phi}{phi}{phi} as the bound states of scalar-quarks {phi}. We also investigate the color-singlet bound states of scalar-quarks {phi} and quarks {psi}, i.e., {phi}{sup {dagger}}{psi}, {psi}{psi}{phi}, and {phi}{phi}{psi}, which we name ''chimera hadrons.'' All the new-type hadrons including {phi} are found to have a large mass even for zero bare scalar-quark mass m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV. We find a ''constituent scalar-quark/quark picture'' for both scalar-quark hadrons and chimera hadrons. Namely, the mass of the new-type hadron composed of m {phi}'s and n {psi}'s, M{sub m{phi}}{sub +n{psi}}, approximately satisfies M{sub m{phi}}{sub +n{psi}}{approx_equal}mM{sub {phi}}+nM{sub {psi}}, where M{sub {phi}} and M{sub {psi}} are the constituent scalar-quark and quark masses, respectively. We estimate the constituent scalar-quark mass M{sub {phi}} for m{sub {phi}}=0 at a{sup -1}{approx_equal}1 GeV as M{sub {phi}}{approx_equal}1.5-1.6 GeV, which is much larger than the constituent quark mass M{sub {psi}}{approx_equal}400 MeV in the chiral limit. Thus, scalar quarks acquire a large mass due to large quantum corrections by gluons in the systems including scalar quarks. Together with other evidences of mass generation of glueballs and charmonia, we conjecture that all colored particles generally acquire a large effective mass due to dressed gluon effects. In addition, the large mass generation of pointlike colored scalar particles indicates that plausible diquarks used in effective hadron models cannot be described as the pointlike particles and should have a much larger size than a{approx_equal}0.2 fm.
Gluon Radiation and Parton Energy Loss
Alexander Kovner; Urs Achim Wiedemann
2003-04-15T23:59:59.000Z
The propagation of hard partons through spatially extended matter leads to medium-modifications of their fragmentation pattern. Here, we review the current status of calculations of the corresponding medium-induced gluon radiation, and how this radiation affects hadronic observables at collider energies.
Extracting gluon condensate from the average plaquette
Lee, Taekoon
2015-01-01T23:59:59.000Z
The perturbative contribution in the average plaquette is subtracted using Borel summation and the remnant of the plaquette is shown to scale as a dim-4 condensate. A critical review is presented of the renormalon subtraction scheme that claimed a dim-2 condensate. The extracted gluon condensate is compared with the latest result employing high order (35-loop) calculation in the stochastic perturbation theory.
Gluon Radiation and Coherent States in Ultrarelativistic Nuclear Collisions
Sergei G. Matinyan; Berndt Mueller; Dirk H. Rischke
1997-05-14T23:59:59.000Z
We explore the correspondence between classical gluon radiation and quantum radiation in a coherent state for gluons produced in ultrarelativistic nuclear collisions. The expectation value of the invariant momentum distribution of gluons in the coherent state is found to agree with the gluon number distribution obtained classically from the solution of the Yang-Mills equations. A criterion for the applicability of the coherent state formalism to the problem of radiation in ultrarelativistic nucleus-nucleus collisions is discussed. This criterion is found to be fulfilled for midrapidity gluons with perturbative transverse momenta larger than about 1-2 GeV and produced in collisions between valence partons.
A General Effective Action for Quark Matter and its Application to Color Superconductivity
Philipp T. Reuter
2006-02-13T23:59:59.000Z
I derive a general effective theory for hot and/or dense quark matter. After introducing general projection operators for hard and soft quark and gluon degrees of freedom, I explicitly compute the functional integral for the hard quark and gluon modes in the QCD partition function. Upon appropriate choices for the projection operators one recovers various well-known effective theories such as the Hard Thermal Loop/ Hard Dense Loop Effective Theories as well as the High Density Effective Theory by Hong and Schaefer. I then apply the effective theory to cold and dense quark matter and show how it can be utilized to simplify the weak-coupling solution of the color-superconducting gap equation. In general, one considers as relevant quark degrees of freedom those within a thin layer of width 2 Lambda_q around the Fermi surface and as relevant gluon degrees of freedom those with 3-momenta less than Lambda_gl. It turns out that it is necessary to choose Lambda_q << Lambda_gl, i.e., scattering of quarks along the Fermi surface is the dominant process. Moreover, this special choice of the two cutoff parameters Lambda_q and Lambda_gl facilitates the power-counting of the numerous contributions in the gap-equation. In addition, it is demonstrated that both the energy and the momentum dependence of the gap function has to be treated self-consistently in order to determine the imaginary part of the gap function. For quarks close to the Fermi surface the imaginary part is calculated explicitly and shown to be of sub-subleading order in the gap equation.
WHOT-QCD Collaboration; :; Y. Maezawa; N. Ukita; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya
2007-02-13T23:59:59.000Z
We study Polyakov loop correlations and spatial Wilson loop at finite Temperature in two-flavor QCD simulations with the RG-improved gluon action and the clover-improved Wilson quark action on a $ 16^3 \\times 4$ lattice. From the line of constant physics at $m_{\\rm PS}/m_{\\rm V}=0.65$ and 0.80, we extract the heavy-quark free energies, the effective running coupling $g_{\\rm eff}(T)$ and the Debye screening mass $m_D(T)$ for various color channels of heavy quark--quark and quark--anti-quark pairs above the critical temperature. The free energies are well approximated by the screened Coulomb form with the appropriate Casimir factors at high temperature. The magnitude and the temperature dependence of the Debye mass are compared to those of the next-to-leading order thermal perturbation theory and to a phenomenological formula in terms of $g_{\\rm eff}(T)$. We make a comparison between our results with the Wilson quark action and the previous results with the staggered quark action. The spatial string tension is also studied in the high temperature phase and is compared to the next-to-next-leading order prediction in an effective theory with dimensional reduction.
Search for a heavy vector boson decaying to two gluons in pp? collisions at ?s=1.96 TeV
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Aaltonen, T.; Adelman, J.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; et al
2012-12-01T23:59:59.000Z
We present a search for a new heavy vector boson Z' that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z'?g*g. We study the case where the off-shell gluon g* converts to a pair of top quarks, leading to a final state of tt¯g. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb?¹ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limitsmore »on the production cross section times branching ratio of this chromophilic Z' at 95% confidence level from 300 to 40 fb for Z' masses ranging from 400 to 1000 GeV/c², respectively.« less
Search for a heavy vector boson decaying to two gluons in pp? collisions at ?s=1.96 TeV
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Aaltonen, T.; Adelman, J.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J. A.; Arisawa, T.; Artikov, A.; Asaadi, J.; Ashmanskas, W.; Auerbach, B.; Aurisano, A.; Azfar, F.; Badgett, W.; Bae, T.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Barria, P.; Bartos, P.; Bauce, M.; Bedeschi, F.; Behari, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Beretvas, A.; Bhatti, A.; Bisello, D.; Bizjak, I.; Bland, K. R.; Blumenfeld, B.; Bocci, A.; Bodek, A.; Bortoletto, D.; Boudreau, J.; Boveia, A.; Brigliadori, L.; Bromberg, C.; Brucken, E.; Budagov, J.; Budd, H. S.; Burkett, K.; Busetto, G.; Bussey, P.; Buzatu, A.; Calamba, A.; Calancha, C.; Camarda, S.; Campanelli, M.; Campbell, M.; Canelli, F.; Carls, B.; Carlsmith, D.; Carosi, R.; Carrillo, S.; Carron, S.; Casal, B.; Casarsa, M.; Castro, A.; Catastini, P.; Cauz, D.; Cavaliere, V.; Cavalli-Sforza, M.; Cerri, A.; Cerrito, L.; Chen, Y. C.; Chertok, M.; Chiarelli, G.; Chlachidze, G.; Chlebana, F.; Cho, K.; Chokheli, D.; Chung, W. H.; Chung, Y. S.; Ciocci, M. A.; Clark, A.; Clarke, C.; Compostella, G.; Convery, M. E.; Conway, J.; Corbo, M.; Cordelli, M.; Cox, C. A.; Cox, D. J.; Crescioli, F.; Cuevas, J.; Culbertson, R.; Dagenhart, D.; d’Ascenzo, N.; Datta, M.; de Barbaro, P.; Dell’Orso, M.; Demortier, L.; Deninno, M.; Devoto, F.; d’Errico, M.; Di Canto, A.; Di Ruzza, B.; Dittmann, J. R.; D’Onofrio, M.; Donati, S.; Dong, P.; Dorigo, M.; Dorigo, T.; Ebina, K.; Elagin, A.; Eppig, A.; Erbacher, R.; Errede, S.; Ershaidat, N.; Eusebi, R.; Farrington, S.; Feindt, M.; Fernandez, J. P.; Field, R.; Flanagan, G.; Forrest, R.; Frank, M. J.; Franklin, M.; Freeman, J. C.; Funakoshi, Y.; Furic, I.; Gallinaro, M.; Garcia, J. E.; Garfinkel, A. F.; Garosi, P.; Gerberich, H.; Gerchtein, E.; Giagu, S.; Giakoumopoulou, V.; Giannetti, P.; Gibson, K.; Ginsburg, C. M.; Giokaris, N.; Giromini, P.; Giurgiu, G.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldin, D.; Goldschmidt, N.; Golossanov, A.; Gomez, G.; Gomez-Ceballos, G.; Goncharov, M.; González, O.; Gorelov, I.; Goshaw, A. T.; Goulianos, K.; Grinstein, S.; Grosso-Pilcher, C.; Group, R. C.; Guimaraes da Costa, J.; Hahn, S. R.; Halkiadakis, E.; Hamaguchi, A.; Han, J. Y.; Happacher, F.; Hara, K.; Hare, D.; Hare, M.; Harr, R. F.; Hatakeyama, K.; Hays, C.; Heck, M.; Heinrich, J.; Herndon, M.; Hewamanage, S.; Hocker, A.; Hopkins, W.; Horn, D.; Hou, S.; Hughes, R. E.; Hurwitz, M.; Husemann, U.; Hussain, N.; Hussein, M.; Huston, J.; Introzzi, G.; Iori, M.; Ivanov, A.; James, E.; Jang, D.; Jayatilaka, B.; Jeon, E. J.; Jindariani, S.; Jones, M.; Joo, K. K.; Jun, S. Y.; Junk, T. R.; Kamon, T.; Karchin, P. E.; Kasmi, A.; Kato, Y.; Ketchum, W.; Keung, J.; Khader, M.; Khotilovich, V.; Kilminster, B.; Kim, D. H.; Kim, H. S.; Kim, J. E.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, Y. K.; Kim, Y. J.; Kimura, N.; Kirby, M.; Klimenko, S.; Knoepfel, K.; Kondo, K.; Kong, D. J.; Konigsberg, J.; Kotwal, A. V.; Kreps, M.; Kroll, J.; Krop, D.; Kruse, M.; Krutelyov, V.; Kuhr, T.; Kurata, M.; Kwang, S.; Laasanen, A. T.; Lami, S.; Lammel, S.; Lancaster, M.; Lander, R. L.; Lannon, K.; Lath, A.; Latino, G.; LeCompte, T.; Lee, E.; Lee, H. S.; Lee, J. S.; Lee, S. W.; Leo, S.; Leone, S.; Lewis, J. D.; Limosani, A.; Lin, C.-J.; Lindgren, M.; Lipeles, E.; Lister, A.; Litvintsev, D. O.; Liu, C.; Liu, H.; Liu, Q.; Liu, T.; Lockwitz, S.; Loginov, A.; Lucchesi, D.; Lueck, J.; Lujan, P.; Lukens, P.; Lungu, G.; Lys, J.; Lysak, R.; Madrak, R.; Maeshima, K.; Maestro, P.; Malik, S.; Manca, G.; Manousakis-Katsikakis, A.; Margaroli, F.; Marino, C.; Martínez, M.; Mastrandrea, P.; Matera, K.; Mattson, M. E.; Mazzacane, A.; Mazzanti, P.; McFarland, K. S.; McIntyre, P.; McNulty, R.; Mehta, A.; Mehtala, P.; Mesropian, C.; Miao, T.; Mietlicki, D.; Mitra, A.; Miyake, H.; Moed, S.; Moggi, N.; Mondragon, M. N.; Moon, C. S.; Moore, R.; Morello, M. J.; Morlock, J.; Movilla Fernandez, P.; Mukherjee, A.; Muller, Th.; Murat, P.; Mussini, M.; Nachtman, J.; Nagai, Y.; Naganoma, J.; Nakano, I.; Napier, A.; Nett, J.; Neu, C.; Neubauer, M. S.; Nielsen, J.; Nodulman, L.; Noh, S. Y.; Norniella, O.; Oakes, L.; Oh, S. H.; Oh, Y. D.; Oksuzian, I.; Okusawa, T.; Orava, R.; Ortolan, L.; Pagan Griso, S.; Pagliarone, C.; Palencia, E.; Papadimitriou, V.; Paramonov, A. A.; Patrick, J.; Pauletta, G.; Paulini, M.; Paus, C.; Pellett, D. E.; Penzo, A.; Phillips, T. J.; Piacentino, G.; Pianori, E.; Pilot, J.; Pitts, K.; Plager, C.; Pondrom, L.; Poprocki, S.; Potamianos, K.; Prokoshin, F.; Pranko, A.; Ptohos, F.; Punzi, G.; Rahaman, A.; Ramakrishnan, V.; Ranjan, N.; Rao, K.; Redondo, I.; Renton, P.; Rescigno, M.; Riddick, T.; Rimondi, F.; Ristori, L.; Robson, A.; Rodrigo, T.; Rodriguez, T.; Rogers, E.; Rolli, S.; Roser, R.; Ruffini, F.; Ruiz, A.; Russ, J.; Rusu, V.
2012-12-01T23:59:59.000Z
We present a search for a new heavy vector boson Z' that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of Z'?g*g. We study the case where the off-shell gluon g* converts to a pair of top quarks, leading to a final state of tt¯g. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb?¹ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limits on the production cross section times branching ratio of this chromophilic Z' at 95% confidence level from 300 to 40 fb for Z' masses ranging from 400 to 1000 GeV/c², respectively.
Erich W. Varnes
2008-10-20T23:59:59.000Z
A review is presented of the current experimental status of the top quark sector of the standard model. The measurements summarized include searches for electroweak single top production, the latest results on the ttbar production cross section, and searches for new physics in top quark production and decay. In addition, the recent measurement of the top quark mass to a precision of 0.7% is highlighted
Quark Condensates: Flavour Dependence
R. Williams; C. S. Fischer; M. R. Pennington
2007-03-23T23:59:59.000Z
We determine the q-bar q condensate for quark masses from zero up to that of the strange quark within a phenomenologically successful modelling of continuum QCD by solving the quark Schwinger-Dyson equation. The existence of multiple solutions to this equation is the key to an accurate and reliable extraction of this condensate using the operator product expansion. We explain why alternative definitions fail to give the physical condensate.
Sketching the pion's valence-quark generalised parton distribution
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Mezrag, C.; Chang, L.; Moutarde, H.; Roberts, C.D.; Rodríguez-Quintero, J.; Sabatié, F.; Schmidt, S.M.
2015-02-01T23:59:59.000Z
In order to learn effectively from measurements of generalised parton distributions (GPDs), it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL) truncation of QCD’s Dyson–Schwinger equations and exemplified via the pion’s valence dressed-quark GPD, Hv?(x, ?, t). Our analysis focuses primarily on ?=0, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting Hv?(x, ?=±1, t)with the pion’s valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to definemore »the pion’s valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for Hv?(x, 0, t), expressed as the Radon transform of a single amplitude. Therewith we obtain results for Hv?(x, 0, t)and the associated impact-parameter dependent distribution, qv?(x, |#2;b?|), which provide a qualitatively sound picture of the pion’s dressed-quark structure at ahadronic scale. We evolve the distributions to a scale ?=2GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.« less
Eric Laenen
2008-09-18T23:59:59.000Z
I review how the top quark is embedded in the Standard Model and some its proposed extensions, and how it manifests itself in various hadron collider signals.
Christian Schwanenberger
2010-04-28T23:59:59.000Z
Highlights of top quark physics presented at the 2009 Europhysics Conference on High Energy Physics from 16-22 July 2009 in Krakow, Poland, are reviewed.
Search of anomalous $Wtb$ couplins in single top quark prodution at D0
Joshi, Jyoti; Beri, Suman; /Panjab U.
2011-12-01T23:59:59.000Z
The large mass of the top quark, close to the electroweak symmetry-breaking scale, makes it a good candidate for probing physics beyond the Standard Model, including possible anomalous couplings. D0 has made measurements of single top quark production using 5.4 fb{sup -1} of integrated luminosity. We examine the data to study the Lorentz structure of the Wtb coupling. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. In 2009, the electroweak single top quark production was observed by the D0 and CDF collaborations. Electroweak production of top quarks at the Tevatron proceeds mainly via the decay of a time-like virtual W boson accompanied by a bottom quark in the s-channel (tb = t{bar b} + {bar t}b), or via the exchange of a space-like virtual W boson between a light quark and a bottom quark in the t-channel (tqb = tq{bar b} + {bar t}qb, where q refers to the light quark). For a top quark mass of 172.5 GeV, The Standard Model (SM) prediction of single top production rate at next-to-leading order with soft-gluon contributions at next-to-next-to-leading order are 1.04 {+-} 0.04 pb (s-channel) and 2.26 {+-} 0.12 pb (t-channel). The large mass of the top quark implies that it has large couplings to the electroweak symmetry breaking sector of the SM and may have non-standard interactions with the weak gauge bosons. Single top quark production provides a unique probe to study the interactions of the top quark with the W boson.
Gluon effects may rule out the existence of color superconducting strange stars
E. J. Ferrer; V. de la Incera; L. Paulucci
2015-05-24T23:59:59.000Z
Compact astrophysical objects are a window for the study of strongly interacting nuclear matter given the conditions in their interiors, which are not reproduced in a laboratory environment. Much has been debated about their composition with possibilities ranging from a simple mixture of mostly protons and neutrons to deconfined quark matter. Recent observations on the mass of two pulsars, PSR J1614-2230 and PSR J0348+0432, have posed a great restriction on their composition, since the equation of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but it can get substantially stiffer since in the high-dense medium a repulsive vector interaction channel is opened. Nevertheless, we show that once gluon effects are considered, the equation of state of quark matter in the color-flavor-locked phase of color superconductivity becomes softer decreasing the maximum stellar mass that can be reached when not considering their influence. This may indicate that stars made entirely of color superconducting matter can only be favored to describe compact stars if the repulsive vector constant is high enough.
Gluon effects may rule out the existence of color superconducting strange stars
E. J. Ferrer; V. de la Incera; L. Paulucci
2015-01-26T23:59:59.000Z
Compact astrophysical objects are a window for the study of strongly interacting nuclear matter given the conditions in their interiors, which are not reproduced in a laboratory environment. Much has been debated about their composition with possibilities ranging from a simple mixture of mostly protons and neutrons to deconfined quark matter. Recent observations on the mass of two pulsars, PSR J1614-2230 and PSR J0348+0432, have posed a great restriction on their composition, since the equation of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but it can get substantially stiffer since in the high-dense medium a repulsive vector interaction channel is opened. Nevertheless, in this letter we show that once gluon effects are considered, the equation of state of quark matter in the color-flavor-locked phase of superconductivity becomes significantly smoother constraining the maximum stellar mass that can be reached to values much smaller than the observed ones. This may indicate that stars made entirely of color superconducting matter are not favored to describe compact stars.
Gluon effects may rule out the existence of color superconducting strange stars
Ferrer, E J; Paulucci, L
2015-01-01T23:59:59.000Z
Compact astrophysical objects are a window for the study of strongly interacting nuclear matter given the conditions in their interiors, which are not reproduced in a laboratory environment. Much has been debated about their composition with possibilities ranging from a simple mixture of mostly protons and neutrons to deconfined quark matter. Recent observations on the mass of two pulsars, PSR J1614-2230 and PSR J0348+0432, have posed a great restriction on their composition, since the equation of state must be hard enough to support masses of about at least two solar masses. The onset of quarks tends to soften the equation of state, but it can get substantially stiffer since in the high-dense medium a repulsive vector interaction channel is opened. Nevertheless, in this letter we show that once gluon effects are considered, the equation of state of quark matter in the color-flavor-locked phase of superconductivity becomes significantly smoother constraining the maximum stellar mass that can be reached to val...
B. L. Ioffe
2010-07-03T23:59:59.000Z
It is demonstrated, that chirality violating condensates in massless QCD arise entirely from zero mode solutions of Dirac equations in arbitrary gluon fields. The model is suggested, where the zero mode solutions are the ones for quarks, moving in the instanton field. Basing on this model were calculated the quark condensate magnetic susceptibilities of dimensions $3(\\chi)$ and 5 ($\\kappa$ and $\\xi$). The good considence of the values $\\chi,\\kappa$ and $\\xi$, obtained in this approach with ones, found from the hadronic spectrum ia a serious argument in favour, that instantons are the only source of chirality violating condensates in QCD. The temperature dependence of the quark condensate is discussed. It is shown that the phase transition, corresponding to the $T$-dependence of the quark condensate $\\alpha(T)$ as an order parameter, is of the type of crossover.
Quantum chromodynamics quark benzene
Jialun Ping; Chengrong Deng; Fan Wang; T. Goldman
2007-11-28T23:59:59.000Z
A six-quark state with the benzene-like structure is proposed and studied based on color string model. The calculation with the quadratic confinement show that such structure has the lowest energy among the various hidden color six-quark structures proposed so far. Its possible effect on $NN$ scattering is discussed.
Quark Number Susceptibility with Finite Quark Mass in Holographic QCD
Kyung-il Kim; Youngman Kim; Shingo Takeuchi; Takuya Tsukioka
2011-10-31T23:59:59.000Z
We study the effect of a finite quark mass on the quark number susceptibility in the framework of holographic QCD. We work in a bottom-up model with a deformed AdS black hole and D3/D7 model to calculate the quark number susceptibility at finite temperature with/without a finite quark chemical potential. As expected the finite quark mass suppresses the quark number susceptibility. We find that at high temperatures $T\\ge 600$ MeV the quark number susceptibility of light quarks and heavy quarks are almost equal in the bottom-up model. This indicates that the heavy quark like charm contribution to thermodynamics of a QCD-like system may start to become significant at temperatures $T\\sim 600$ MeV. In D3/D7 model, we focus on the competition between the quark chemical potential, which enhances the quark number susceptibility, and the quark mass that suppresses the susceptibility. We observe that depending on the relative values of the quark mass and the quark chemical potential, the quark number susceptibility shows a diverging or converging behavior. We also calculate the chiral susceptibility in D3/D7 model to support the observation made with the quark number susceptibility.
Two-loop helicity amplitudes for the production of two off-shell electroweak bosons in gluon fusion
Caola, Fabrizio; Melnikov, Kirill; Smirnov, Alexander V; Smirnov, Vladimir A
2015-01-01T23:59:59.000Z
We compute the part of the two-loop virtual amplitude for the process $gg \\to V_1 V_2 \\to (l_1 \\bar l'_{1}) (l_2 \\bar l'_2)$, where $V_{1,2}$ are arbitrary electroweak gauge bosons, that receives contributions from loops of massless quarks. Invariant masses of electroweak bosons are allowed to be different from each other. Our result provides an important ingredient for improving the description of gluon fusion contribution to the production of four-lepton final states at the LHC.
Forward-backward asymmetry in top quark-antiquark production
Abazov, Victor Mukhamedovich [Dubna, JINR; Abbott, Braden Keim [Oklahoma U.; Acharya, Bannanje Sripath [Tata Inst.; Adams, Mark Raymond [Illinois U., Chicago; Adams, Todd [Florida State U.; Alexeev, Guennadi D [Dubna, JINR; Alkhazov, Georgiy D [St. Petersburg, INP; Alton, Andrew K [Michigan U.; Augustana Coll., Sioux Falls; Alverson, George O [Northeastern U.; Alves, Gilvan Augusto [Rio de Janeiro, CBPF; Aoki, Masato [Fermilab; Louisiana Tech. U.
2011-12-12T23:59:59.000Z
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb^{-1}, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
Forward-backward asymmetry in top quark-antiquark production
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Abazov, Victor Mukhamedovich; Abbott, Braden Keim; Acharya, Bannanje Sripath; Adams, Mark Raymond; Adams, Todd; Alexeev, Guennadi D; Alkhazov, Georgiy D; Alton, Andrew K; Alverson, George O; Alves, Gilvan Augusto; et al
2011-12-12T23:59:59.000Z
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%.more »The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.« less
Forward-backward asymmetry in top quark-antiquark production
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Abazov, Victor Mukhamedovich [Dubna, JINR; Abbott, Braden Keim [Oklahoma U.; Acharya, Bannanje Sripath [Tata Inst.; Adams, Mark Raymond [Illinois U., Chicago; Adams, Todd [Florida State U.; Alexeev, Guennadi D [Dubna, JINR; Alkhazov, Georgiy D [St. Petersburg, INP; Alton, Andrew K [Michigan U.; Augustana Coll., Sioux Falls; Alverson, George O [Northeastern U.; Alves, Gilvan Augusto [Rio de Janeiro, CBPF; Aoki, Masato [Fermilab; Louisiana Tech. U.
2011-12-12T23:59:59.000Z
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of 5.4 fb-1, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 ± 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 ± 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 ± 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
Challenges to quantum chromodynamics: Anomalous spin, heavy quark, and nuclear phenomena
Brodsky, S.J.
1989-11-01T23:59:59.000Z
The general structure of QCD meshes remarkably well with the facts of the hadronic world, especially quark-based spectroscopy, current algebra, the approximate point-like structure of large momentum transfer inclusive reactions, and the logarithmic violation of scale invariance in deep inelastic lepton-hadron reactions. QCD has been successful in predicting the features of electron-positron and photon-photon annihilation into hadrons, including the magnitude and scaling of the cross sections, the shape of the photon structure function, the production of hadronic jets with patterns conforming to elementary quark and gluon subprocesses. The experimental measurements appear to be consistent with basic postulates of QCD, that the charge and weak currents within hadrons are carried by fractionally-charged quarks, and that the strength of the interactions between the quarks, and gluons becomes weak at short distances, consistent with asymptotic freedom. Nevertheless in some cases, the predictions of QCD appear to be in dramatic conflict with experiment. The anomalies suggest that the proton itself as a much more complex object than suggested by simple non-relativistic quark models. Recent analyses of the proton distribution amplitude using QCD sum rules points to highly-nontrival proton structure. Solutions to QCD in one-space and one-time dimension suggest that the momentum distributions of non-valence quarks in the hadrons have a non-trival oscillatory structure. The data seems also to be suggesting that the intrinsic'' bound state structure of the proton has a non- negligible strange and charm quark content, in addition to the extrinsic'' sources of heavy quarks created in the collision itself. 144 refs., 46 figs., 2 tabs.
Measurement of b-quark Jet Shapes at CDF
Lister, Alison; /Zurich, ETH
2006-03-01T23:59:59.000Z
The main topic of this thesis is the measurement of b-quark jet shapes at CDF. CDF is an experiment located at Fermilab, in the United States, which studies proton-antiproton collisions at a center of mass energy of 1.96TeV. To reach this energy, the particles are accelerated using the Tevatron accelerator which is currently the highest energy collider in operation. The data used for this analysis were taken between February 2002 and September 2004 and represent an integrated luminosity of about 300 pb{sup -1}. This is the first time that b-quark jet shapes have been measured at hadron colliders. The basis of this measurement lies in the possibility of enhancing the b-quark jet content of jet samples by requiring the jets to be identified as having a displaced vertex inside the jet cone. Such jets are called tagged. This enhances the b-quark jet fraction from about 5% before tagging to 20-40% after tagging, depending on the transverse momentum of the jets. I verified that it is possible to apply this secondary vertex tagging algorithm to different cone jet algorithms (MidPoint and JetClu) and different cone sizes (0.4 and 0.7). I found that the performance of the algorithm does not change significantly, as long as the sub-cone inside which tracks are considered for the tagging is kept at the default value of 0.4. Because the b-quark purity of the jets is still relatively low, it is necessary to extract the shapes of b-quark jets in a statistical manner from the jet shapes both before and after tagging. The other parameters that enter into the unfolding equation used to extract the b-quark jet shapes are the b-jet purities, the biases due to the tagging requirement both for b- and nonbjets and the hadron level corrections. The last of these terms corrects the measured b-jet shapes back to the shapes expected at hadron level which makes comparisons with theoretical models and other experimental results possible. This measurement shows that, despite relatively large systematic uncertainties, the measured b-quark jet shapes are significantly different from those expected from the so-called Pythia Tune A Monte Carlo simulation, the most widely used Leading Order Monte Carlo model at CDF. This difference can be mostly attributed to the fact that the fraction of b-quark jets that originate from flavour creation (where a single b-quark is expected inside the same jet cone) over those that originate from gluon splitting (where two b-quarks are expected to be inside the same jet cone) is slightly different in the Pythia Tune A Monte Carlo predictions than in data. This measurement can help in the tuning of the fraction of gluon splitting to flavour creation b-quark jets in the Monte Carlo simulation. This tuning is particularly important for the extrapolation up to LHC energies where many searches will involve b-quark jets. During the first year of my thesis work, I worked on the implementation of a prototype detector control system for the electromagnetic calorimeter which is being built for the CMS experiment at CERN. The prototype which I implemented was used to monitor and control the high voltage, low voltage, cooling and precision temperature monitoring systems during the summer 2003 test-beam. This was one of the first, almost complete, systems implemented and used by an LHC experiment for test-beam monitoring.
analyzing dynamical gluon: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
HEP - Experiment (arXiv) Summary: We discuss the production of the composite Higgs boson in topcolor models via the gluon fusion process. We consider the contribution of...
anomalous gluon spectral: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
non-perturbative gluon spectral functions at finite temperature in quenched QCD with the maximum entropy method. We also provide a closed loop equation for the spectral function...
Top-quark transverse-momentum distributions in t-channel single-top production
Nikolaos Kidonakis
2013-06-15T23:59:59.000Z
I present approximate next-to-next-to-leading-order (NNLO) top-quark transverse momentum, pT, distributions in t-channel single-top production. These distributions are derived from next-to-next-to-leading-logarithm (NNLL) soft-gluon resummation. Theoretical results for the single top as well as the single antitop pT distributions are shown for LHC and Tevatron energies.
Peters, Yvonne
2011-12-01T23:59:59.000Z
Since its discovery in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, the top quark has undergone intensive studies. Besides the Tevatron experiments, with the start of the LHC in 2010 a top quark factory started its operation. It is now possible to measure top quark properties simultaneously at four different experiments, namely ATLAS and CMS at LHC and CDF and D0 at Tevatron. Having collected thousands of top quarks each, several top quark properties have been measured precisely, while others are being measured for the first time. In this article, recent measurements of top quark properties from ATLAS, CDF, CMS and D0 are presented, using up to 5.4 fb{sup -1} of integrated luminosity at the Tevatron and 1.1 fb{sup -1} at the LHC. In particular, measurements of the top quark mass, mass difference, foward backward charge asymmetry, t{bar t} spin correlations, the ratio of branching fractions, W helicity, anomalous couplings, color flow and the search for flavor changing neutral currents are discussed.
Yvonne Peters; for the Atlas Collaboration; CDF Collaboration; CMS Collaboration; D0 Collaboration
2011-12-02T23:59:59.000Z
Since its discovery in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, the top quark has undergone intensive studies. Besides the Tevatron experiments, with the start of the LHC in 2010 a top quark factory started its operation. It is now possible to measure top quark properties simultaneously at four different experiments, namely ATLAS and CMS at LHC and CDF and D0 at Tevatron. Having collected thousands of top quarks each, several top quark properties have been measured precisely, while others are being measured for the first time. In this article, recent measurements of top quark properties from ATLAS, CDF, CMS and D0 are presented, using up to 5.4 fb-1 of integrated luminosity at the Tevatron and 1.1 fb^-1 at the LHC. In particular, measurements of the top quark mass, mass difference, forward backward charge asymmetry, tt - spin correlations, the ratio of branching fractions, W helicity, anomalous couplings, color flow and the search for flavor changing neutral currents are discussed.
ALICE ATLAS Cover 3 decades of energy
= nuclear particles = mesons, baryons Courtesy Nat. Geographic, Vol. 185, No. 1, 1994 Â Graphics by Chuck Harris (Yale) 6th Odense Winter School on Theoretical Physics, 20 Quark-Gluon Plasma Â· Standard Model?" #12;How to Make Quark Soup!! Nuclear particles (quarks are confined) Melt the particlesQuark Gluon
Gluons in our future | Jefferson Lab
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Efe Yazgan; for the CMS Collaboration
2014-09-12T23:59:59.000Z
Measurements involving top quarks provide important tests of QCD. A selected set of top quark measurements in CMS including the strong coupling constant, top quark pole mass, constraints on parton distribution functions, top quark pair differential cross sections, ttbar+0 and >0 jet events, top quark mass studied using various kinematic variables in different phase-space regions, and alternative top quark mass measurements is presented. The evolution of expected uncertainties in future LHC runs for the standard and alternative top quark mass measurements is also presented.
Phenomenological analysis of Higgs boson production through gluon fusion in association with jets
Greiner, Nicolas; Luisoni, Gionata; Schonherr, Marek; Winter, Jan-Christopher; Yundin, Valery
2015-01-01T23:59:59.000Z
We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. We consider the gluon fusion channel using an effective theory in the large top-quark mass limit. Higgs boson production in gluon fusion constitutes an irreducible background to the vector boson fusion (VBF) process; hence the precise knowledge of its characteristics is a prerequisite for any measurement in the VBF channel. The calculation is carried out at next-to-leading order (NLO) in QCD in a fully automated way by combining the two programs GoSam and Sherpa. We present numerical results for a large variety of observables for both standard cuts and VBF selection cuts. We find that for all jet multiplicities the NLO corrections are sizeable. This is particularly true in the presence of kinematic selections enhancing the VBF topology, which are based on vetoing additional jet activity. In this case, precise predictions for the background can be made using our calculation by...
Tony M. Liss
2012-12-03T23:59:59.000Z
I review the latest results on properties of the top quark from the Tevatron and the LHC, including results measured in $t\\bar{t}$ and single-top events on the mass, width, couplings, and spin correlations.
Hill, Christopher S.; /UC, Santa Barbara
2004-12-01T23:59:59.000Z
The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.
Heidi Schellman and Ann Heinson
2009-03-12T23:59:59.000Z
Fermilab researchers Heidi Schellman and Ann Heinson take a whimsical look at the recent announcement of the discovery of the single top quark, by Fermilab's CDF and DZero experiments.
Running coupling corrections to inclusive gluon production
W. A. Horowitz; Yuri V. Kovchegov
2011-06-27T23:59:59.000Z
We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. At leading order there are three powers of fixed coupling; in our final answer, these three couplings are replaced by seven factors of running coupling: five in the numerator and two in the denominator, forming a `septumvirate' of running couplings, analogous to the `triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the `septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling k_T-factorization formula for gluon production which includes non-linear small-x evolution.
National Nuclear Security Administration (NNSA)
Nuclear Physics: This category recognizes the distinct nature of quark- gluon plasma research and its foundations in the broader field of nuclear physics. At normal...
assisted tandem reactions: Topics by E-print Network
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photon and electron scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever...
assisted reaction route: Topics by E-print Network
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photon and electron scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever...
allergic reaction related: Topics by E-print Network
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photon and electron scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever...
ABSTRACTS FOR PAPERS SUBMITTED
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if they carry any information on the initial quark-gluon plasma, we have developed a multiphase transport model (AMPT), which includes both initial partonic and final hadronic...
autosynthetic micropyretic reactions: Topics by E-print Network
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scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic...
alpha6he reaction rozpad: Topics by E-print Network
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scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic...
arthus reaction: Topics by E-print Network
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scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic...
antigen-antibody reactions: Topics by E-print Network
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scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic...
andp31d pp32 reactions: Topics by E-print Network
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scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic...
acute dystonic reactions: Topics by E-print Network
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scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic...
Infrared Limit of Gluon Amplitudes at Strong Coupling
Evgeny I. Buchbinder
2007-07-27T23:59:59.000Z
In this note, we propose that the infrared structure of gluon amplitudes at strong coupling can be fully extracted from a local consideration near cusps. This is consistent with field theory and correctly reproduces the infrared divergences of the four-gluon amplitude at strong coupling calculated recently by Alday and Maldacena.
Higgs Production by Gluon initiated Weak Boson Fusion
M. M. Weber
2007-09-17T23:59:59.000Z
The gluon-gluon induced terms for Higgs production through weak-boson fusion are calculated. They form a finite and gauge-invariant subset of the NNLO corrections in the strong coupling constant. This is also the lowest order with sizeable t-channel colour exchange contributions, leading to additional hadronic activity between the outgoing jets.
Strange and charm quark contributions to the anomalous magnetic moment of the muon
Bipasha Chakraborty; C. T. H. Davies; G. C. Donald; R. J. Dowdall; J. Koponen; G. P. Lepage; T. Teubner
2014-06-02T23:59:59.000Z
We describe a new technique to determine the contribution to the anomalous magnetic moment of the muon coming from the hadronic vacuum polarization using lattice QCD. Our method reconstructs the Adler function, using Pad\\'{e} approximants, from its derivatives at $q^2=0$ obtained simply and accurately from time-moments of the vector current-current correlator at zero spatial momentum. We test the method using strange quark correlators on large-volume gluon field configurations that include the effect of up and down (at physical masses), strange and charm quarks in the sea at multiple values of the lattice spacing and multiple volumes and show that 1% accuracy is achievable. For the charm quark contributions we use our previously determined moments with up, down and strange quarks in the sea on very fine lattices. We find the (connected) contribution to the anomalous moment from the strange quark vacuum polarization to be $a_\\mu^s = 53.41(59) \\times 10^{-10}$, and from charm to be $a_\\mu^c = 14.42(39)\\times 10^{-10}$. These are in good agreement with flavour-separated results from non-lattice methods, given caveats about the comparison. The extension of our method to the light quark contribution and to that from the quark-line disconnected diagram is straightforward.
Measuring the flavor asymmetry in the sea quarks of the proton
Reimer, Paul E.; /Argonne
2010-01-01T23:59:59.000Z
The proton is a composite object made of fundamental, strongly-interacting quarks. Many of the features of the proton can be described by a simple picture based on three valence quarks bound by the exchange of gluons. However, protons are much more complex objects with the vast majority of their mass dynamically generated by Quantum Chromodynamics (QCD). This mass manifests itself through a 'sea' of gluons and quark-antiquark pairs. By measuring Drell-Yan scattering, the Fermilab E-906/SeaQuest experiment will study the sea quark distribution in the proton and, in particular, the unusually large asymmetry between anti-up and anti-down quarks measured by earlier Drell-Yan experiments. This asymmetry cannot simply be generated through pair creation, but rather indicates an underlying, fundamental antiquark component in the proton. Using the same technique, E-906/SeaQuest will also investigate the differences between the antiquark distributions of the free proton and a proton bound in a nucleus. Nuclear binding is expected to modify the quark distributions and it has long been known that the overall quark distributions are different (the EMC effect). Surprisingly, present data suggests that the antiquark distributions and hence the sea distributions are not modified. To accomplish these goals, the experiment will used a 120 GeV proton beam extracted from the Fermilab Main Injector. While the experiment will be taking advantage of equipment from earlier Drell-Yan experiments, the changes in kinematics of the experiment require several, significant upgrades to the spectrometer. The collaboration expects to begin data collection in fall 2010.
Continuum Study of Heavy Quark Diffusion
Thomas Neuhaus
2015-04-28T23:59:59.000Z
We report on a lattice investigation of heavy quark momentum diffusion within the pure SU(3) plasma above the deconfinement transition with the quarks treated to leading order in the heavy mass expansion. We measure the relevant "colour-electric" Euclidean correlator and based on several lattice spacing's perform the continuum extrapolation. This is necessary not only to remove cut-off effects but also the analytic continuation for the extraction of transport coefficients is well-defined only when a continuous function of the Euclidean time variable is available. We pay specific attention to scale setting in SU(3). In particular we present our determination for the critical temperature $T_c=1/({N_\\tau}a) $ at values of $N_\\tau \\le 22$.
Physics with boosted top quarks
Elin Bergeaas Kuutmann
2014-08-29T23:59:59.000Z
The production at the LHC of boosted top quarks (top quarks with a transverse momentum that greatly exceeds their rest mass) is a promising process to search for phenomena beyond the Standard Model. In this contribution several examples are discussed of new techniques to reconstruct and identify (tag) the collimated decay topology of the boosted hadronic decays of top quarks. Boosted top reconstruction techniques have been utilized in searches for new physical phenomena. An overview is given of searches by ATLAS, CDF and CMS for heavy new particles decaying into a top and an anti-top quark, vector-like quarks and supersymmetric partners to the top quark.
Next-to-next-to-leading order soft gluon corrections in top quark hadroproduction.
Kidonakis, Nikolaos; Vogt, Ramona
. Likewise, the subleading terms stop and reverse the downward trend of the PIM scaling functions. The 1PI gg contribution will still be positive while the PIM will still be negative but the difference may not be as large as before. Using the alternate... cross section is not as large as previously, due to the subleading terms. The average of the two kinematics is just above the NLO cross sections for both energies. Going to higher scales increases all the NNLO corrections so that both kinematics choices...
Discrepancy between hadron matter and quark-gluon matter in net charge transfer fluctuation
Dai-Mei Zhou; Xiao-Mei Li; Bao-Guo Dong; Ben-Hao Sa
2006-02-08T23:59:59.000Z
A parton and hadron cascade model, PACIAE, is employed to investigate the net charge transfer fluctuation within $|\\eta|$=1 in Au+Au collisions at $\\sqrt{s_{NN}}$=200 GeV. It is turned out that the observable of net charge transfer fluctuation, $\\kappa$, in hadronic final state (HM) is nearly a factor of 3 to 5 larger than that in initial partonic state (QGM). However, only twenty percent of the net charge transfer fluctuation in the QGM can survive the hadronization
Bose-Einstein correlations and the transition time from QCD plasma to hadrons
A. Bialas; K. Zalewski
2012-10-07T23:59:59.000Z
It is pointed out that the size of the interaction region, as determined from HBT analyses, is increased due to the transition time necessary the convert the quarks and gluons into hadrons. A rough estimate yields an increase of R_HBT by about 15%.
LHC limits on the top-Higgs in models with strong top-quark dynamics
Chivukula, R. Sekhar; Simmons, Elizabeth H.; Coleppa, Baradhwaj; Logan, Heather E.; Martin, Adam [Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States); Ottawa-Carleton Institute for Physics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada); Theoretical Physics Department, Fermilab, Batavia, Illinois 60510 (United States)
2011-11-01T23:59:59.000Z
LHC searches for the standard model Higgs boson in WW or ZZ decay modes place strong constraints on the top-Higgs state predicted in many models with new dynamics preferentially affecting top quarks. Such a state couples strongly to top quarks, and is therefore produced through gluon fusion at a rate enhanced relative to the rate for the standard model Higgs boson. A top-Higgs state with mass less than 300 GeV is excluded at 95% C.L. if the associated top-pion has a mass of 150 GeV, and the constraint is even stronger if the mass of the top-pion state exceeds the top-quark mass or if the top-pion decay constant is a substantial fraction of the weak scale. These results have significant implications for theories with strong top dynamics, such as topcolor-assisted technicolor, top-seesaw models, and certain Higgsless models.
Quark helicity flip and the transverse spin dependence of inclusive DIS
Andrei Afanasev; Mark Strikman; Christian Weiss
2007-05-21T23:59:59.000Z
Inclusive DIS with unpolarized beam exhibits a subtle dependence on the transverse target spin, arising from the interference of one-photon and two-photon exchange amplitudes in the cross section. We argue that this observable probes mainly the quark helicity-flip amplitudes induced by the non-perturbative vacuum structure of QCD (spontaneous chiral symmetry breaking). This conjecture is based on (a) the absence of significant Sudakov suppression of the helicity-flip process if soft gluon emission in the quark subprocess is limited by the chiral symmetry breaking scale mu^2_{chiral} >> Lambda^2_{QCD}; (b) the expectation that the quark helicity-conserving twist-3 contribution is small. The normal target spin asymmetry is estimated to be of the order 10^{-4} in the kinematics of the planned Jefferson Lab Hall A experiment.
Gluon condensation and deconfinement critical density in nuclear matter
M. Baldo; P. Castorina; D. Zappala'
2004-10-07T23:59:59.000Z
An upper limit to the critical density for the transition to the deconfined phase, at zero temperature, has been evaluated by analyzing the behavior of the gluon condensate in nuclear matter. Due to the non linear baryon density effects, the upper limit to the critical density, \\rho_c turns out about nine times the saturation density, rho_0 for the value of the gluon condensate in vacuum =0.012 GeV^4. For neutron matter \\rho_c \\simeq 8.5 \\rho_0. The dependence of the critical density on the value of the gluon condensate in vacuum is studied.
Soft-Gluon Production Due to a Gluon Loop in a Constant Chromo-Electric Background Field
Gouranga C. Nayak; Peter van Nieuwenhuizen
2005-05-24T23:59:59.000Z
We obtain an exact result for the soft gluon production and its p_T distribution due to a gluon loop in a constant chromo-electric background field E^a with arbitrary color. Unlike Schwinger's result for e^+e^- pair production in QED which depends only on one gauge invariant quantity, the Electric field E, we find that the p_T distribution of the gluons depend on two gauge invariant quantities, E^aE^a and [d_{abc}E^aE^bE^c]^2.
Quark Structure of the Nucleon and Angular Asymmetry of Proton-Neutron Hard Elastic Scattering
Carlos G. Granados; Misak M. Sargsian
2009-07-29T23:59:59.000Z
We investigate an asymmetry in the angular distribution of hard elastic proton-neutron scattering with respect to 90deg center of mass scattering angle. We demonstrate that the magnitude of the angular asymmetry is related to the helicity-isospin symmetry of the quark wave function of the nucleon. Our estimate of the asymmetry within the quark-interchange model of hard scattering demonstrates that the quark wave function of a nucleon based on the exact SU(6) symmetry predicts an angular asymmetry opposite to that of experimental observations. On the other hand the quark wave function based on the diquark picture of the nucleon produces an asymmetry consistent with the data. Comparison with the data allowed us to extract the relative sign and the magnitude of the vector and scalar diquark components of the quark wave function of the nucleon. These two quantities are essential in constraining QCD models of a nucleon. Overall, our conclusion is that the angular asymmetry of a hard elastic scattering of baryons provides a new venue in probing quark-gluon structure of baryons and should be considered as an important observable in constraining the theoretical models.
Transverse-momentum dependent parton distribution functions beyond leading twist in quark models
C. Lorcé; B. Pasquini; P. Schweitzer
2015-02-03T23:59:59.000Z
Higher-twist transverse momentum dependent parton distribution functions (TMDs) are a valuable probe of the quark-gluon dynamics in the nucleon, and play a vital role for the explanation of sizable azimuthal asymmetries in hadron production from unpolarized and polarized deep-inelastic lepton-nucleon scattering observed in experiments at CERN, DESY and Jefferson Lab. The associated observables are challenging to interpret, and still await a complete theoretical explanation, which makes guidance from models valuable. In this work we establish the formalism to describe unpolarized higher-twist TMDs in the light-front framework based on a Fock-space expansion of the nucleon state in terms of free on-shell parton states. We derive general expressions and present numerical results in a practical realization of this picture provided by the light-front constituent quark model. We review several other popular quark model approaches including free quark ensemble, bag, spectator and chiral quark-soliton model. We discuss how higher-twist TMDs are described in these models, and obtain results for several TMDs not discussed previously in literature. This study contributes to the understanding of non-perturbative properties of subleading twist TMDs. The results from the light-front constituent quark model are also compared to available phenomenological information, showing a satisfactory agreement.
Rapidity evolution of gluon TMD from low to moderate x
I. Balitsky; A. Tarasov
2015-05-08T23:59:59.000Z
We study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x \\ll 1$ to linear evolution at moderate $x \\sim 1$.
Evolution of gluon TMD at low and moderate x
I. Balitsky; A. Tarasov
2014-11-05T23:59:59.000Z
We study how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small $x\\ll 1$ to linear double-logarithmic evolution at moderate $x\\sim 1$.
Paul B. Mackenzie
1992-12-14T23:59:59.000Z
Lattice calculations of heavy quark systems provide very good measures of the lattice spacing, a key element in recent determinations of the strong coupling constant using lattice methods. They also provide excellent testing grounds for lattice methods in general. I review recent phenomenological and technical developments in this field.
Distribution of linearly polarized gluons inside a large nucleus
Andreas Metz; Jian Zhou
2011-09-08T23:59:59.000Z
The distribution of linearly polarized gluons inside a large nucleus is studied in the framework of the color glass condensate. We find that the Weizs\\"acker-Williams distribution saturates the positivity bound at large transverse momenta and is suppressed at small transverse momenta, whereas the dipole distribution saturates the bound for any value of the transverse momentum. We also discuss processes in which both distributions of linearly polarized gluons can be probed.
Gluon distribution in proton at soft and hard pp collisions
Lykasov, G I; Grinyuk, A A; Poghosyan, M; Dolbilov, A G
2011-01-01T23:59:59.000Z
We analyze the inclusive spectra of hadrons produced in $pp$ collisions at high energies in the mid-rapidity region within the soft QCD and perturbative QCD assuming the possible creation of the soft gluons at low intrinsic transverse momenta $k_t$. From the best description of the LHC data we found the parametrization of the unintegrated gluon distribution which at low $k_t$ is different from the one obtained within the perturbative QCD.
Axions and saxions from the primordial supersymmetric plasma and extra radiation signatures
Graf, Peter; Steffen, Frank Daniel, E-mail: graf@mpp.mpg.de, E-mail: steffen@mpp.mpg.de [Max-Planck-Institut für Physik, Föhringer Ring 6, D–80805 Munich (Germany)
2013-02-01T23:59:59.000Z
We calculate the rate for thermal production of axions and saxions via scattering of quarks, gluons, squarks, and gluinos in the primordial supersymmetric plasma. Systematic field theoretical methods such as hard thermal loop resummation are applied to obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling. We calculate the thermally produced yield and the decoupling temperature for both axions and saxions. For the generic case in which saxion decays into axions are possible, the emitted axions can constitute extra radiation already prior to big bang nucleosynthesis and well thereafter. We update associated limits imposed by recent studies of the primordial helium-4 abundance and by precision cosmology of the cosmic microwave background and large scale structure. We show that the trend towards extra radiation seen in those studies can be explained by late decays of thermal saxions into axions and that upcoming Planck results will probe supersymmetric axion models with unprecedented sensitivity.
The Multimedia Project Quarked!
Bean, Alice
2011-01-01T23:59:59.000Z
Can exposure to fundamental ideas about the nature of matter help motivate children in math and science and support the development of their understanding of these ideas later? Physicists, designers, and museum educators at the University of Kansas created the Quarked!(tm) Adventures in the subatomic Universe project to provide an opportunity for youth to explore the subatomic world in a fun and user friendly way. The project components include a website (located at http://www.quarked.org) and hands-on education programs. These are described and assessment results are presented. Questions addressed include the following. Can you engage elementary and middle school aged children with concepts related to particle physics? Can young children make sense of something they can't directly see? Do teachers think the material is relevant to their students?
Detecting a Higgs Pseudoscalar with a Z Boson Produced in Bottom Quark Fusion
Chung Kao; Shankar Sachithanandam
2005-06-08T23:59:59.000Z
We investigate the prospects of detecting a Higgs pseudoscalar ($A^0$) in association with a $Z$ gauge boson produced from bottom quark fusion ($b\\bar{b} \\to ZA^0$) at the CERN Large Hadron Collider (LHC). A general two Higgs doublet model and the minimal supersymmetric standard model are adopted to study the discovery potential of $pp \\to ZA^0 \\to \\ell \\bar{\\ell} b\\bar{b} +X (\\ell = e, \\mu)$, via $b\\bar{b} \\to ZA^0$ with physics backgrounds and realistic cuts. Promising results are found for $m_A \\alt 400$ GeV in a general two Higgs doublet model when the heavier Higgs scalar ($H^0$) can decay into a $Z$ boson and a Higgs pseudoscalar ($H^0 \\to ZA^0$). We compare the production rates from bottom quark fusion ($b\\bar{b} \\to ZA^0$) and gluon fusion ($gg \\to ZA^0$) and find that they are complementary processes to produce $ZA^0$ in hadron collisions. While gluon fusion is the major source for producing a Higgs pseudoscalar associated with a $Z$ boson at the LHC for $\\tan\\beta \\alt 10$, bottom quark fusion can make dominant contributions for $\\tan\\beta \\agt 10$.
Santopinto, E
2015-01-01T23:59:59.000Z
In this contribution, we briefly discuss the results for charmonium and bottomonium spectra with self-energy corrections in the unquenched quark model, due to the coupling to the meson-meson continuum. The UQM formalism can be extended to include also the effects of hybrid mesons, i.e. hybrid loops. Finally, we discuss the results of a calculation of hybrid mesons spectrum in Coulomb Gauge QCD.
E. Santopinto; J. Ferretti
2015-03-10T23:59:59.000Z
In this contribution, we briefly discuss the results for charmonium and bottomonium spectra with self-energy corrections in the unquenched quark model, due to the coupling to the meson-meson continuum. The UQM formalism can be extended to include also the effects of hybrid mesons, i.e. hybrid loops. Finally, we discuss the results of a calculation of hybrid mesons spectrum in Coulomb Gauge QCD.
Measuring the flavor asymmetry in the sea quarks of the proton with the Drell-Yan process.
Reimer, P. E. (Physics)
2011-01-01T23:59:59.000Z
The proton is a composite object made of fundamental, strongly interacting quarks. Many of the features of the proton can be described by a simple picture based on three 'valence' quarks bound by the exchange of gluons. However, protons are much more complex objects with the vast majority of their mass dynamically generated by quantum chromodynamics (QCD). This mass manifests itself through a 'sea' of gluons and quark-antiquark pairs. By measuring Drell-Yan scattering, the Fermilab E-906/Drell-Yan experiment will study the sea quark distribution in the proton and, in particular, the unusually large asymmetry between anti-up and anti-down quarks measured by earlier Drell-Yan experiments. This asymmetry cannot simply be generated through pair creation, but rather indicates an underlying, fundamental antiquark component in the proton. Using the same technique, the E-906/SeaQuest experiment will also investigate the differences between the antiquark distributions of the free proton and a proton bound in a nucleus. Nuclear binding is expected to modify the quark distributions and it has long been known that the overall quark distributions are different (the EMC effect). Surprisingly, present data suggest, however, that the antiquark distributions are not modified. To accomplish these goals, the experiment will use a 120 GeV proton beam extracted from the Fermilab Main Injector. While the experiment will be taking advantage of equipment from earlier Drell-Yan experiments, the changes in kinematics of the experiment require several, significant upgrades to the spectrometer. Japanese institutions, including Tokyo Institute of Technology, KEK, RIKEN, Kyoto University and Yamagata University, are making substantial contributions to this upgrade. The collaboration expects to begin data collection in Summer, 2010.
Top quark pair production and top quark properties at CDF
Chang-Seong Moon
2014-11-01T23:59:59.000Z
We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into $b$-quarks, performed by measuring the ratio $R$ between the top quark branching fraction to $b$-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element $|V_{tb}|$ from the ratio $R$ is discussed. We also present the latest measurements on the forward-backward asymmetry ($A_{FB}$) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in $t\\bar t$ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.
Emamuddin, M.; Yasmin, S.; Mamun, A. A. [Department of Physics, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh and Post Graduate Education, Training and Research Centre, National University, Gazipur-1704 (Bangladesh)
2013-04-15T23:59:59.000Z
The nonlinear propagation of dust-acoustic waves in a dusty plasma whose constituents are negatively charged dust, Maxwellian ions with two distinct temperatures, and electrons following q-nonextensive distribution, is investigated by deriving a number of nonlinear equations, namely, the Korteweg-de-Vries (K-dV), the modified Korteweg-de-Vries (mK-dV), and the Gardner equations. The basic characteristics of the hump (positive potential) and dip (negative potential) shaped dust-acoustic (DA) Gardner solitons are found to exist beyond the K-dV limit. The effects of two temperature ions and electron nonextensivity on the basic features of DA K-dV, mK-dV, and Gardner solitons are also examined. It has been observed that the DA Gardner solitons exhibit negative (positive) solitons for qq{sub c}) (where q{sub c} is the critical value of the nonextensive parameter q). The implications of our results in understanding the localized nonlinear electrostatic perturbations existing in stellar polytropes, quark-gluon plasma, protoneutron stars, etc. (where ions with different temperatures and nonextensive electrons exist) are also briefly addressed.
Karolos Potamianos
2011-12-01T23:59:59.000Z
We present the recent results of top-quark physics using up to 6 fb$^{-1}$ of $p\\bar{p}$ collisions analyzed by the CDF collaboration. The large number of top quark events analyzed, of the order of several thousands, allows stringent checks of the standard model predictions. Also, the top quark is widely believed to be a window to new physics. We present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.
Potamianos, Karolos
2011-12-01T23:59:59.000Z
We present the recent results of top-quark physics using up to 6 fb{sup -1} of p{bar p} collisions analyzed by the CDF collaboration. The large number of top quark events analyzed, of the order of several thousands, allows stringent checks of the standard model predictions. Also, the top quark is widely believed to be a window to new physics. We present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.
Infrared behavior of gluon and ghost propagators from asymmetric lattices
Attilio Cucchieri; Tereza Mendes
2006-04-18T23:59:59.000Z
We present a numerical study of the lattice Landau gluon and ghost propagators in three-dimensional pure SU(2) gauge theory. Data have been obtained using asymmetric lattices (V = 20^2 X 40, 20^2 X 60, 8^2 X 64, 8^2 X 140, 12^2 X 140 and 16^2 X 140) for the lattice coupling beta = 3.4, in the scaling region. We find that the gluon (respectively ghost) propagator is suppressed (respec. enhanced) at small momenta in the limit of large lattice volume V. By comparing these results with data obtained using symmetric lattices (V = 60^3 and 140^3), we find that both propagators suffer from systematic effects in the infrared region (p \\lesssim 650 MeV). In particular, the gluon (respec. ghost) propagator is less IR-suppressed (respec. enhanced) than in the symmetric case. We discuss possible implications of the use of asymmetric lattices.
Heavy Quark production at HERA and Heavy Quark contributions
Detlef Bartsch, University of Bonn on behalf of the ZEUS and H1 Collaborations Â· Introduction Â· Heavy 1500 0 100 200 300 400 electrons positrons low E HERA-1 HERA-2 Detlef Bartsch Heavy Quark production Detlef Bartsch Heavy Quark production at HERA, Feb. 23rd 2008 3 #12;pQCD approximations Massive scheme
Infrared exponents of gluon and ghost propagators from Lattice QCD
O. Oliveira; P. J. Silva
2007-10-02T23:59:59.000Z
The compatibility of the pure power law infrared solution of QCD Dyson-Schwinger equations (DSE) and lattice data for the gluon and ghost propagators in Landau gauge is discussed. For the gluon propagator, the lattice data is compatible with the DSE infrared solution with an exponent $\\kappa\\sim0.53$, measured using a technique that suppresses finite volume effects and allows to model these corrections to the lattice data. For the ghost propagator, the lattice data does not seem to follow the infrared DSE power law solution.
Small Quarkonium states in an anisotropic QCD plasma
Yun Guo
2008-05-16T23:59:59.000Z
We determine the hard-loop resummed propagator in an anisotropic QCD plasma in general covariant gauges and define a potential between heavy quarks from the Fourier transform of its static limit. We find that the potential exhibits angular dependence and that binding of very small quarkonium states is stronger than in an isotropic plasma.
Large Component QCD and Theoretical Framework of Heavy Quark Effective Field Theory
Yue-Liang Wu
2006-10-14T23:59:59.000Z
Based on a large component QCD derived directly from full QCD by integrating over the small components of quark fields with $|{\\bf p}| < E + m_Q$, an alternative quantization procedure is adopted to establish a basic theoretical framework of heavy quark effective field theory (HQEFT) in the sense of effective quantum field theory. The procedure concerns quantum generators of Poincare group, Hilbert and Fock space, anticommutations and velocity super-selection rule, propagator and Feynman rules, finite mass corrections, trivialization of gluon couplings and renormalization of Wilson loop. The Lorentz invariance and discrete symmetries in HQEFT are explicitly illustrated. Some new symmetries in the infinite mass limit are discussed. Weak transition matrix elements and masses of hadrons in HQEFT are well defined to display a manifest spin-flavor symmetry and $1/m_Q$ corrections. A simple trace formulation approach is explicitly demonstrated by using LSZ reduction formula in HQEFT, and shown to be very useful for parameterizing the transition form factors via $1/m_Q$ expansion. As the heavy quark and antiquark fields in HQEFT are treated on the same footing in a fully symmetric way, the quark-antiquark coupling terms naturally appear and play important roles for simplifying the structure of transition matrix elements, and for understanding the concept of `dressed heavy quark' - hadron duality. In the case that the `longitudinal' and `transverse' residual momenta of heavy quark are at the same order of power counting, HQEFT provides a consistent approach for systematically analyzing heavy quark expansion in terms of $1/m_Q$. Some interesting features in applications of HQEFT to heavy hadron systems are briefly outlined.
L. Cerrito
2004-07-16T23:59:59.000Z
Preliminary results on the measurement of the top quark mass at the Tevatron Collider are presented. In the dilepton decay channel, the CDF Collaboration measures m{sub t} = 175.0{sub -16.9}{sup +17.4}(stat.){+-}8.4(syst.) GeV/c{sup 2}, using a sample of {approx} 126 pb{sup -1} of proton-antiproton collision data at {radical}s = 1.96 TeV (Run II). In the lepton plus jets channel, the CDF Collaboration measures 177.5{sub -9.4}{sup +12.7}(stat.) {+-} 7.1(syst.) GeV/c{sup 2}, using a sample of {approx} 102 pb{sup -1} at {radical}s = 1.96 TeV. The D0 Collaboration has newly applied a likelihood technique to improve the analysis of {approx} 125 pb{sup -1} of proton-antiproton collisions at {radical}s = 1.8 TeV (Run I), with the result: m{sub t} = 180.1 {+-} 3.6(stat.) {+-}3.9(syst.) GeV/c{sup 2}. The latter is combined with all the measurements based on the data collected in Run I to yield the most recent and comprehensive experimental determination of the top quark mass: m{sub t} = 178.0 {+-} 2.7(stat.) {+-} 3.3(syst.) GeV/c{sup 2}.
Quarks with Integer Electric Charge
J. LaChapelle
2015-01-26T23:59:59.000Z
Within the context of the Standard Model, quarks are placed in a $(\\mathbf{3},\\mathbf{2})\\oplus (\\mathbf{3},\\bar{\\mathbf{2}})$ matter field representation of $U_{EW}(2)$. Although the quarks carry unit intrinsic electric charge in this construction, anomaly cancellation constrains the Lagrangian in such a way that the quarks' associated currents couple to the photon with the usual 2/3 and 1/3 fractional electric charge associated with conventional quarks. The resulting model is identical to the Standard Model in the $SU_C(3)$ sector: However, in the $U_{EW}(2)$ sector it is similar but not necessarily equivalent. Off hand, the model appears to be phenomenologically equivalent to the conventional quark model in the electroweak sector for experimental conditions that preclude observation of individual constituent currents. On the other hand, it is conceivable that detailed analyses for electroweak reactions may reveal discrepancies with the Standard Model in high energy and/or large momentum transfer reactions. The possibility of quarks with integer electric charge strongly suggests the notion that leptons and quarks are merely different manifestations of the same underlying field. A speculative model is proposed in which a phase transition is assumed to occur between $SU_C(3)\\otimes U_{EM}(1)$ and $U_{EM}(1)$ regimes. This immediately; explains the equality of lepton/quark generations and lepton/hadron electric charge, relates neutrino oscillations to quark flavor mixing, reduces the free parameters of the Standard Model, and renders the issue of quark confinement moot.
Relation between quark-antiquark potential and quark-antiquark free energy in hadronic matter
Zhen-Yu Shen; Xiao-Ming Xu
2014-06-19T23:59:59.000Z
We study the relation between the quark-antiquark potential and the quark-antiquark free energy in hadronic matter. While a temperature is over the critical temperature, the potential of a heavy quark and a heavy antiquark almost equals the free energy, otherwise the quark-antiquark potential is substantially larger than the quark-antiquark free energy. While a temperature is below the critical temperature, the quark-antiquark free energy can be taken as the quark-antiquark potential.
Non-linear BFKL dynamics: color screening vs. gluon fusion
R. Fiore; P. V. Sasorov; V. R. Zoller
2012-11-01T23:59:59.000Z
A feasible mechanism of unitarization of amplitudes of deep inelastic scattering at small values of Bjorken $x$ is the gluon fusion. However, its efficiency depends crucially on the vacuum color screening effect which accompanies the multiplication and the diffusion of BFKL gluons from small to large distances. From the fits to lattice data on field strength correlators the propagation length of perturbative gluons is $R_c\\simeq 0.2-0.3$ fermi. The probability to find a perturbative gluon with short propagation length at large distances is suppressed exponentially. It changes the pattern of (dif)fusion dramatically. The magnitude of the fusion effect appears to be controlled by the new dimensionless parameter $\\sim R_c^2/8B$, with the diffraction cone slope $B$ standing for the characteristic size of the interaction region. It should slowly $\\propto 1/\\ln Q^2$ decrease at large $Q^2$. Smallness of the ratio $R_c^2/8B$ makes the non-linear effects rather weak even at lowest Bjorken $x$ available at HERA. We report the results of our studies of the non-linear BFKL equation which has been generalized to incorporate the running coupling and the screening radius $R_c$ as the infrared regulator.
On quark-lepton complementarity
F. Gonzalez-Canales; A. Mondragon
2006-06-16T23:59:59.000Z
Recent measurements of the neutrino solar mixing angle and the Cabibbo angle satisfy the empirical relation theta_{sol} + theta_{C} ~ 45^{o}. This relation suggests the existence of a correlation between the mixing matrices of leptons and quarks, the so called quark-lepton complementarity. Here, we examine the possibility that this correlation originates in the strong hierarchy in the mass spectra of quarks and charged leptons, and the seesaw mechanism that gives mass to the Majorana neutrinos. In a unified treatment of quarks and leptons in which the mass matrices of all fermions have a similar Fritzsch texture, we calculate the mixing matrices V_{CKM} and U_{MNSP} as functions of quark and lepton masses and only two free parameters, in very good agreement with the latest experimental values on masses and mixings. Three essential ingredients to explain the quark-lepton complementarity relation are identified: the strong hierarchy in the mass spectra of quarks and charged leptons, the normal seesaw mechanism and the assumption of maximal CP violation in the lepton sector.
On quark-lepton complementarity
Gonzalez Canales, F.; Mondragon, A. [Instituto de Fisica, UNAM, 04510, Mexico D.F. (Mexico)
2006-09-25T23:59:59.000Z
Recent measurements of the neutrino solar mixing angle and the Cabibbo angle satisfy the empirical relation {theta}{sub sol} + {theta}{sub C} {approx_equal} ({pi}/4). This relation suggests the existence of a correlation between the mixing matrices of leptons and quarks, the so called quark-lepton complementarity. Here, we examine the possibility that this correlation originates in the strong hierarchy in the mass spectra of quarks and charged leptons, and the seesaw mechanism that gives mass to the Majorana neutrinos. In a unified treatment of quarks and leptons in which the mass matrices of all fermions have a similar Fritzsch texture, we calculate the mixing matrices VCKM and UMNSP as functions of quark and lepton masses and only two free parameters, in very good agreement with the latest experimental values on masses and mixings. Three essential ingredients to explain the quark-lepton complementarity relation are identified: the strong hierarchy in the mass spectra of quarks and charged leptons, the normal seesaw mechanism and the assumption of maximal CP violation in the lepton sector.
Color Glass Condensate and Glasma
F. Gelis
2012-11-26T23:59:59.000Z
We review the Color Glass Condensate effective theory, that describes the gluon content of a high energy hadron or nucleus, in the saturation regime. The emphasis is put on applications to high energy heavy ion collisions. After describing initial state factorization, we discuss the Glasma phase, that precedes the formation of an equilibrated quark-gluon plasma. We end this review with a presentation of recent developments in the study of the isotropization and thermalization of the quark-gluon plasma.
Shear Viscosity of Quark Matter
W. M. Alberico; S. Chiacchiera; H. Hansen; A. Molinari; M. Nardi
2007-07-30T23:59:59.000Z
We consider the shear viscosity of a system of quarks and its ratio to the entropy density above the critical temperature for deconfinement. Both quantities are derived and computed for different modeling of the quark self-energy, also allowing for a temperature dependence of the effective mass and width. The behaviour of the viscosity and the entropy density is argued in terms of the strength of the coupling and of the main characteristics of the quark self-energy. A comparison with existing results is also discussed.
Wicke, Daniel; /Wuppertal U., Dept. Math.
2009-08-01T23:59:59.000Z
The aim of particle physics is the understanding of elementary particles and their interactions. The current theory of elementary particle physics, the Standard Model, contains twelve different types of fermions which (neglecting gravity) interact through the gauge bosons of three forces. In addition a scalar particle, the Higgs boson, is needed for theoretical consistency. These few building blocks explain all experimental results found in the context of particle physics, so far. Nevertheless, it is believed that the Standard Model is only an approximation to a more complete theory. First of all the fourth known force, gravity, has withstood all attempts to be included until now. Furthermore, the Standard Model describes several features of the elementary particles like the existence of three families of fermions or the quantisation of charges, but does not explain these properties from underlying principles. Finally, the lightness of the Higgs boson needed to explain the symmetry breaking is difficult to maintain in the presence of expected corrections from gravity at high scales. This is the so called hierarchy problem. In addition astrophysical results indicate that the universe consists only to a very small fraction of matter described by the Standard Model. Large fractions of dark energy and dark matter are needed to describe the observations. Both do not have any correspondence in the Standard Model. Also the very small asymmetry between matter and anti-matter that results in the observed universe built of matter (and not of anti-matter) cannot be explained until now. It is thus an important task of experimental particle physics to test the predictions of the Standard Model to the best possible accuracy and to search for deviations pointing to necessary extensions or modifications of our current theoretical understanding. The top quark was predicted to exist by the Standard Model as the partner of the bottom quark. It was first observed in 1995 by the Tevatron experiments CDF and D0 and was the last of the quarks to be discovered. As the partner of the bottom quark the top quark is expected to have quantum numbers identical to that of the other known up-type quarks. Only the mass is a free parameter. We now know that it is more than 30 times heavier than the next heaviest quark, the bottom quark. Thus, within the Standard Model all production and decay properties are fully defined. Having the complete set of quarks further allows to verify constraints that the Standard Model puts on the sum of all quarks or particles. This alone is reason enough to experimentally study the top quark properties. The high value of the top quark mass and its closeness to the electroweak scale has inspired people to speculate that the top quark could have a special role in the electroweak symmetry breaking. Confirming the expected properties of the top quark experimentally establishes the top quark as we expect it to be. Any deviation from the expectations gives hints to new physics that may help to solve the outstanding questions. In this review the recent results on top quark properties obtained by the Tevatron experiments CDF and D0 are summarized. At the advent of the LHC special emphasis is given to the basic measurement methods and the dominating systematic uncertainties. After a short introduction to the Standard Model and the experimental environment in the remainder of this chapter, Chapter 2 describes the current status of top quark mass measurements. Then measurments of interaction properties are described in Chapter 3. Finally, Chapter 4 deals with analyses that consider hypothetical particles beyond the Standard Model in the observed events.
Top quark studies at hadron colliders
Sinervo, P.K. [Univ. of Toronto, Ontario (Canada)
1997-01-01T23:59:59.000Z
The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag b quark jets in candidate events. The most recent measurements of top quark properties by the CDF and DO Collaborations are reviewed, including the top quark cross section, mass, branching fractions, and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.
Higher twists in polarized DIS and the size of the constituent quark
Alexander Sidorov; Christian Weiss
2006-02-15T23:59:59.000Z
The spontaneous breaking of chiral symmetry implies the presence of a short-distance scale in the QCD vacuum, which phenomenologically may be associated with the ''size'' of the constituent quark, rho {approx} 0.3 fm. We discuss the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon operators determining the leading power (1/Q{sup 2}-) corrections to the moments of the nucleon spin structure functions. We argue that the flavor-nonsinglet twist-4 matrix element, f{sub 2}{sup u-d}, has a sizable negative value of the order rho{sup -2}, due to the presence of sea quarks with virtualities {approx} rho{sup -2} in the proton wave function. The twist-3 matrix element, d{sub 2}, is not related to the scale rho{sup -2}. Our arguments support the results of previous calculations of the matrix elements in the instanton vacuum model. We show that this qualitative picture is in agreement with the phenomenological higher-twist correction extracted from an NLO QCD fit to the world data on g{sub 1}{sup p} and g{sub 1}{sup n}, which include recent data from the Jefferson Lab Hall A and COMPASS experiments. We comment on the implications of the short-distance scale rho for quark-hadron duality and the x-dependence of higher-twist contributions.
Top Quark Production at the Tevatron Collider
Liang Li
2011-07-21T23:59:59.000Z
Top quark physics has been a rich testing ground for the standard model since the top quark discovery in 1995. The large mass of top quark suggests that it could play a special role in searches for new phenomena. In this paper I provide an overview of recent top quark production cross section measurements from both CDF and D0 collaborations and also some new physics searches done in the top quark sector.
Top Quark Production at the Tevatron Collider
Li, Liang; /UC, Riverside
2011-07-01T23:59:59.000Z
Top quark physics has been a rich testing ground for the standard model since the top quark discovery in 1995. The large mass of top quark suggests that it could play a special role in searches for new phenomena. In this paper I provide an overview of recent top quark production cross section measurements from both CDF and D0 collaborations and also some new physics searches done in the top quark sector.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kong, Kyoungchui; Lee, Hye-Sung; Park, Myeonhun
2014-04-01T23:59:59.000Z
We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 ? deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t ? b W + Z's. This is the same as the dominant topmore »quark decay (t ? b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.« less
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kong, Kyoungchui [Kansas; Lee, Hye-Sung [W&M, JLAB; Park, Myeonhun [Tokyo
2014-04-01T23:59:59.000Z
We suggest top quark decays as a venue to search for light dark force carriers. Top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6 ? deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t ? b W + Z's. This is the same as the dominant top quark decay (t ? b W) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.
A. W. Jung
2014-10-14T23:59:59.000Z
Recent measurements of top-quark properties at the LHC and the Tevatron are presented. Most recent measurements of the top quark mass have been carried out by CMS using $19.7/$fb of $\\sqrt{s} = 8$ TeV data including the study of the dependence on event kinematics. ATLAS uses the full Run I data at $\\sqrt{s} = 7$ TeV for a "3D" measurement that significantly reduces systematic uncertainties. D0 employs the full Run II data using the matrix element method to measure the top quark mass with significantly reduced systematic uncertainties. Many different measurements of the top quark exist to date and the most precise ones per decay channel per experiment have been combined into the first world combination with a relative precision of 0.44%. Latest updates of measurements of production asymmetries include the measurement of the \\ttbar production asymmetry by D0 employing the full Run II data set, by CMS and ATLAS (including the polarization of the top quark) employing both the full data set at $\\sqrt{s} = 7$ TeV. CMS uses the full $\\sqrt{s} = 8$ TeV data to measure the top quark polarization in single top production, the ratio ${\\cal R}$ of the branching fractions ${\\cal B}(t \\rightarrow Wb) / {\\cal B}(t \\rightarrow Wq)$ and to search for flavor changing neutral currents. The results from all these measurements agree well with their respective Standard Model expectation.
Infrared Singularities and Soft Gluon Resummation with Massive Partons
A. Ferroglia; M. Neubert; B. D. Pecjak; L. L. Yang
2010-06-24T23:59:59.000Z
Infrared divergences of QCD scattering amplitudes can be derived from an anomalous dimension matrix, which is also an essential ingredient for the resummation of large logarithms due to soft gluon emissions. We report a recent analytical calculation of the anomalous dimension matrix with both massless and massive partons at two-loop level, which describes the two-loop infrared singularities of any scattering amplitudes with an arbitrary number of massless and massive partons, and also enables soft gluon resummation at next-to-next-to-leading-logarithmic order. As an application, we calculate the infrared poles in the q qbar -> t tbar and gg -> t tbar scattering amplitudes at two-loop order.
Running Coupling Corrections to High Energy Inclusive Gluon Production
W. A. Horowitz; Yuri V. Kovchegov
2010-11-09T23:59:59.000Z
We calculate running coupling corrections for the lowest-order gluon production cross section in high energy hadronic and nuclear scattering using the BLM scale-setting prescription. In the final answer for the cross section the three powers of fixed coupling are replaced by seven factors of running coupling, five in the numerator and two in the denominator, forming a 'septumvirate' of running couplings, analogous to the 'triumvirate' of running couplings found earlier for the small-x BFKL/BK/JIMWLK evolution equations. It is interesting to note that the two running couplings in the denominator of the 'septumvirate' run with complex-valued momentum scales, which are complex conjugates of each other, such that the production cross section is indeed real. We use our lowest-order result to conjecture how running coupling corrections may enter the full fixed-coupling kT-factorization formula for gluon production which includes non-linear small-x evolution.
Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond
David d'Enterria; Krisztian Krajczar; Hannu Paukkunen
2015-04-21T23:59:59.000Z
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 10^4 and 10^5 per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t-tbar cross sections, dominated by gluon fusion processes, are enhanced by 3--8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, although different regions of their differential distributions are depleted due to shadowing or EMC-effect corrections. The rapidity distributions of the decay leptons in t-tbar processes can be used to reduce the uncertainty on the Pb gluon density at high virtualities by up to 30% at the LHC (full heavy-ion programme), and by 70% per FCC-year. The cross sections for single-top production in electroweak processes are also computed, yielding about a factor of 30 smaller number of measurable top-quarks after cuts, per system and per year.
Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond
David d'Enterria; Krisztian Krajczar; Hannu Paukkunen
2015-01-23T23:59:59.000Z
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 10^4 and 10^5 per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t-tbar cross sections, dominated by gluon fusion processes, are enhanced by 3--8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, although different regions of their differential distributions are depleted due to shadowing or EMC-effect corrections. The rapidity distributions of the decay leptons in t-tbar processes can be used to reduce the uncertainty on the Pb gluon density at high virtualities by up to 30% at the LHC (full heavy-ion programme), and by 70% per FCC-year. The cross sections for single-top production in electroweak processes are also computed, yielding about a factor of 30 smaller number of measurable top-quarks after cuts, per system and per year.
Saskia Mioduszewski
2010-09-01T23:59:59.000Z
"Probing the Matter Created at RHIC." Mioduszewski discusses the results from RHIC's experimental collaborations and how researchers hope to create a form of matter in which the basic building blocks of matter -- quarks and gluons -- interact freely in what is called quark gluon plasma.
Long-Range Pseudorapidity Correlations at High pT in sqrt(S_NN) = 200 GeV Au+Au Collisions with STAR
Codrington, Martin John Michael
2012-10-19T23:59:59.000Z
The Quark Gluon Plasma (QGP) is a form of matter in which quarks and gluons are deconfined, and was suggested to be formed in high-energy heavy-ion collisions. Since the discovery of high-pT hadron suppression in central Au+Au collisions...
Progress in Lattice QCD at finite temperature
P. Petreczky
2007-05-19T23:59:59.000Z
I review recent developements in lattice QCD at finite temperature, including the determination of the transition temperature T_c, equation of state and diffenet static screening lengths. The lattice data suggest that at temperatures above 1.5T_c the quark gluon plasma can be considered as gas consisting of quarks and gluons.
Quarks and Antiquarks in Nuclei
Jason R. Smith
2005-08-19T23:59:59.000Z
The Chiral Quark-Soliton model provides the quark and antiquark substructure of the nucleon, which is embedded in nuclear matter. This provides a new way to asses the effects of the nuclear medium on the nucleon. We calculate nuclear binding and saturation, describe the European Muon Collaboration (EMC) effect consistently with Drell-Yan experiments, and predict modifications to the polarized parton distributions. We also calculate the electromagnetic form factors of a bound proton, and find significant modifications of the electromagnetic form factors in the nuclear environment. In every case, the properties of the sea of quark-antiquark pairs in the nucleon are very important, and serve to mitigate the valence quark effect. The changes in the sea quarks when the nucleon is immersed in the nuclear medium are the primary mode by which consistency is maintained with experimental constraints (Drell-Yan data, magnetic moment), while still maintaining a significant effect needed to explain the deep inelastic scattering and polarization transfer data.
Cédric Lorcé
2014-09-16T23:59:59.000Z
The proton spin puzzle issue focused the attention on the parton spin and orbital angular momentum contributions to the proton spin. However, a complete characterization of the proton spin structure requires also the knowledge of the parton spin-orbit correlation. We showed that this quantity can be expressed in terms of moments of measurable parton distributions. Using the available phenomenological information about the valence quarks, we concluded that this correlation is negative, meaning that the valence quark spin and kinetic orbital angular momentum are, in average, opposite. The quark spin-orbit correlation can also be expressed more intuitively in terms of relativistic phase-space distributions, which can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We present here for the first time some examples of the general multipole decomposition of these phase-space distributions.
Quark stars: their influence on Astroparticle Physics
Sanjay K. Ghosh
2008-08-12T23:59:59.000Z
We discuss some of the recent developments in the quark star physics along with the consequences of possible hadron to quark phase transition at high density scenario of neutron stars and their implications on the Astroparticle Physics.
Top Quark Production at the LHC
Francesco Spanò; for the ATLAS; CMS collaborations
2011-12-16T23:59:59.000Z
Top quark production in proton proton collisions at the Large Hadron Collider (LHC) is reviewed using data collected by the ATLAS and CMS detectors. Most recent results on searches for new physics related to top quark production mechanism are included.
Werner Bernreuther
2008-05-09T23:59:59.000Z
The physics perspectives of the production and decay of single top quarks and top quark pairs at the CERN Large Hadron Collider (LHC) are reviewed from a phenomenological point of view.
Quark masses: An environmental impact statement
Kimchi, Itamar
We investigate worlds that lie on a slice through the parameter space of the standard model over which quark masses vary. We allow as many as three quarks to participate in nuclei, while fixing the mass of the electron and ...
Schwarz, Thomas A.; /Michigan U.
2006-01-01T23:59:59.000Z
Quarks, along with leptons and force carrying particles, are predicted by the Standard Model to be the fundamental constituents of nature. In distinction from the leptons, the quarks interact strongly through the chromodynamic force and are bound together within the hadrons. The familiar proton and neutron are bound states of the light ''up'' and ''down'' quarks. The most massive quark by far, the ''top'' quark, was discovered by the CDF and D0 experiments in March, 1995. The new quark was observed in p{bar p} collisions at 1.8 TeV at the Fermilab Tevatron. The mass of the top quark was measured to be 176 {+-} 13 GeV/c{sup 2} and the cross section 6.8{sub -2.4}{sup +3.6} pb. It is the Q = 2/3, T{sub 3} = +1/2 member of the third generation weak-isospin doublet along with the bottom quark. The top quark is the final Standard Model quark to be discovered. Along with whatever is responsible for electroweak symmetry breaking, top quark physics is considered one of the least understood sectors of the Standard Model and represents a front line of our understanding of particle physics. Currently, the only direct measurements of top quark properties come from the CDF and D0 experiments observing p{bar p} collisions at the Tevatron. Top quark production at the Tevatron is almost exclusively by quark-antiquark annihilation, q{bar q} {yields} t{bar t} (85%), and gluon fusion, gg {yields} t{bar t} (15%), mediated by the strong force. The theoretical cross-section for this process is {sigma}{sub t{bar t}} = 6.7 {+-} 0.8 pb for m{sub t} = 175 GeV/c{sup 2}. Top quarks can also be produced at the Tevatron via q{bar b}{prime} {yields} tb and qg {yields} q{prime}tb through the weak interaction. The cross section for these processes is lower (3pb) and the signal is much more difficult to isolate as backgrounds are much higher. The top quark is predicted to decay almost exclusively into a W-boson and a bottom quark (t {yields} Wb). The total decay width t {yields} Wb is {Lambda} = 1.50 GeV. This corresponds to an incredibly short lifetime of 0.5 x 10{sup -24} seconds. This happens so quickly that hadronization and bound states do not take place, which leads to the interesting consequence that the top quark spin information is passed to the decay products.
Top Quark: discovery, present and future Galtieri, The Top Quark, PDG 50th
Galtieri, Lina
1 Top Quark: discovery, present and future Galtieri, The Top Quark, PDG 50th Anniversary. September 23-2006 #12;Chasing the Top Quark 2 Gell-Mann, Zweig uds quarks postulated ('64) GIM mechanism at FNAL 1984 PDG partial listing top should exist Searches at Tristan, PETRA, SPPS, SLC : top not found
Valence Quarks Polarization from COMPASS
A. Korzenev
2007-04-26T23:59:59.000Z
A first evaluation of the polarized valence quark distribution $\\Delta u_v(x)+\\Delta d_v(x)$ from the COMPASS experiment (CERN/SPS) is presented. The data were collected by COMPASS in the years 2002--2004 using a 160 GeV polarized muon beam scattered off a large polarized $^6$LiD target and cover the range $1< Q^2 < 100$ GeV$^2$ and $0.006
Spontaneously broken quark helicity symmetry
Dalley, Simon [Department of Physics, University of Wales Swansea, Singleton Park, Swansea SA2 8PP (United Kingdom); McCartor, Gary [Department of Physics, SMU Dallas, TX 75275 (United States)]. E-mail: mccartor@mail.physics.smu.edu
2006-02-15T23:59:59.000Z
We discuss the origin of chiral-symmetry breaking in the light-cone representation of QCD. In particular, we show how quark helicity symmetry is spontaneously broken in SU (N) gauge theory with massless quarks if that theory has a condensate of fermion light-cone zero modes. The symmetry breaking appears as induced interactions in an effective light-cone Hamiltonian equation based on a trivial vacuum. The induced interaction is crucial for generating a splitting between pseudoscalar and vector meson masses, which we illustrate with spectrum calculations in some 1 + 1-dimensional reduced models of gauge theory.
Top quark Physics at the Tevatron
Yvonne Peters; for the CDF; D0 Collaborations
2012-01-06T23:59:59.000Z
When the heaviest elementary particle known today, the top quark, was discovered in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, a large program to study this particle in details has started. In this article, an overview of the status of top quark physics at the Tevatron is presented. In particular, recent results on top quark production, properties and searches using top quarks are discussed.
Quark condensates and the deconfinement transition
Christian S. Fischer; Jens A. Mueller
2009-08-18T23:59:59.000Z
In this talk we present results on the chiral and the deconfinement transition of quenched QCD from Dyson-Schwinger equations. We determine the ordinary quark condensate signaling the chiral transition and the dual quark condensate signaling the deconfinement transition from the Landau gauge quark propagator evaluated at generalized boundary conditions. We find only slightly different transition temperatures at finite quark masses, whereas the transition temperatures coincide in the chiral limit.
Quark model calculation of the EMC effect
Benesh, C.J.; Goldman, T.; Stephenson, G.J. Jr. [Los Alamos National Laboratory, NM (United States)
1993-10-01T23:59:59.000Z
Using a potential model, we calculate quark distributions for a six-quark quasi-deuteron, including the effects of the Pauli Principle and quark tunneling between nuclei. Using a phenomenological sea distribution, the EMC ratio is calculated and found to be in qualitative agreement with experiment.
Gluon polarisation from high transverse momentum hadron pairs production (COMPASS)
L. Silva; for the COMPASS Collaboration
2010-10-08T23:59:59.000Z
A new preliminary result of a gluon polarisation \\Delta G/G obtained selecting high transverse momentum hadron pairs in DIS events with Q^2>1 (GeV/c)^2 is presented. Data has been collected by COMPASS at CERN during the 2002-2004 years. In the extraction of $\\Delta G/G$ contributions coming from the leading order $\\gamma q$ and QCD processes are taken into account. A new weighting method based on a neural network approach is used. Also a preliminary result of \\Delta G/G for events with Q^2<1 (GeV/c)^2 is presented.
A Colorful Wake for Gerhard Soff
Berndt Müller; Jörg Ruppert
2005-07-18T23:59:59.000Z
We calculate the wake induced in a hot QCD plasma by a fast parton in the framework of linear response theory. We discuss two scenarios: ($i$) a weakly coupled quark-gluon plasma described by hard-thermal loop perturbation theory and ($ii$) a strongly coupled quark-gluon plasma which resembles a quantum liquid. We show that a Mach cone can appear in the second scenario, but not in the first one
Functional-analysis based tool for testing quark-hadron duality
Irinel Caprini; Maarten Golterman; Santiago Peris
2014-07-09T23:59:59.000Z
Quark-hadron duality is a key concept in QCD, allowing for the description of physical hadronic observables in terms of quark-gluon degrees of freedom. The modern theoretical framework for its implementation is Wilson's operator product expansion (OPE), supplemented by analytic extrapolation from large Euclidean momenta, where the OPE is defined, to the Minkowski axis, where observable quantities are defined. Recently, the importance of additional terms in the expansion of QCD correlators near the Minkowski axis, responsible for quark-hadron duality violations (DVs), was emphasized. In this paper we introduce a mathematical tool that might be useful for the study of DVs in QCD. It is based on finding the minimal distance, measured in the $L^\\infty$ norm along a contour in the complex momentum plane, between a class of admissible functions containing the physical amplitude and the asymptotic expansion predicted by the OPE. This minimal distance is given by the norm of a Hankel matrix that can be calculated exactly, using as input the experimental spectral function on a finite interval of the timelike axis. We also comment on the relation between the new functional tool and the more commonly used $\\chi^2$-based analysis. The approach is illustrated on a toy model for the QCD polarization function recently proposed in the literature.
A relativistic constituent quark model
Schlumpf, F.
1993-08-01T23:59:59.000Z
We investigate the predictive power of a relativistic quark model formulated on the light-front. The nucleon electromagnetic form factors, the semileptonic weak decays of the hyperons and the magnetic moments of both baryon octet and decuplet are calculated and found to be in excellent agreement with experiment.
R. Y. Peters
2014-08-10T23:59:59.000Z
Years after its discovery in 1995 by CDF and D0, the top quark still undergoes intense investigations at the Tevatron. Using up to the full Run~II data sample, new measurements of top quark production and properties by the D0 Collaboration are presented. In particular, the first observation of single top quark s-channel production, the measurement of differential ttbar distributions, forward-backward ttbar asymmetry, a new measurement of the top quark mass, and a measurement of the top quark charge are discussed.
Top-Quark Physics Results From LHC
Luca Fiorini
2012-01-30T23:59:59.000Z
The top-quark is a fundamental element of the physics program at the Large Hadron Collider (LHC). We review the current status of the top-quark measurements performed by ATLAS and CMS experiments in pp collisions at sqrt(s)=7 TeV by presenting the recent results of the top-quark production rates, top mass measurements and additional top quark properties. We will also describe the recent searches for physics beyond the Standard Model in the top-quark sector.
Top Quark Physics at the Tevatron
Frederic Deliot; Douglas Glenzinski
2011-10-10T23:59:59.000Z
We review the field of top-quark physics with an emphasis on experimental techniques. The role of the top quark in the Standard Model of particle physics is summarized and the basic phenomenology of top-quark production and decay is introduced. We discuss how contributions from physics beyond the Standard Model could affect top-quark properties or event samples. The many measurements made at the Fermilab Tevatron, which test the Standard Model predictions or probe for direct evidence of new physics using the top-quark event samples, are reviewed here.
. Genik II,27 K. Genser,36 C. E. Gerber,37 Y. Gershtein,58 R. Gilmartin,35 G. Ginther,53 B. GoÂ´mez,5 G. GoÂ´mez
Gluon distribution functions and Higgs boson production at moderate transverse momentum
Sun P.; Yuan F.; Xiao, B.W.
2011-11-04T23:59:59.000Z
We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the transverse momentum-dependent factorization formalism. In addition to the usual azimuthal symmetric transverse momentum-dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the transverse momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the small-x naive kt-factorization in the dilute region and find that the azimuthal correlated gluon distribution contribution is consistently taken into account. The result agrees with the transverse momentum-dependent factorization formalism. We comment on the possible breakdown of the naive kt-factorization in the dense medium region, due to the unique behaviors for the gluon distributions.
LPM Interference and Cherenkov-like Gluon Bremsstrahlung in DenseMatter
Majumder, Abhijit; Wang, Xin-Nian
2005-07-26T23:59:59.000Z
Gluon bremsstrahlung induced by multiple parton scattering in a finite dense medium has a unique angular distribution with respect to the initial parton direction. A dead-cone structure with an opening angle; theta2{sub 0}; approx 2(1-z)/(zLE) for gluons with fractional energy z arises from the Landau-Pomeran chuck-Migdal (LPM) interference. In a medium where the gluon's dielectric constant is; epsilon>1, the LPM interference pattern is shown to become Cherenkov-like with an increased opening angle determined by the dielectric constant$/cos2/theta{sub c}=z+(1-z)//epsilon$. For a large dielectric constant/epsilon; gg 1+2/z2LE, the corresponding total radiative parton energy loss is about twice that from normal gluon bremsstrahlung. Implications of this Cherenkov-like gluon bremsstrahlung to the jet correlation pattern in high-energy heavy-ion collisions is discussed.
Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond
d'Enterria, David; Paukkunen, Hannu
2015-01-01T23:59:59.000Z
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 10^4 and 10^5 per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t-tbar cross sections, dominated by gluon fusion processes, are enhanced by 3--8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, altho...
Wang, Zhehui (Los Alamos, NM); Barnes, Cris W. (Santa Fe, NM)
2002-01-01T23:59:59.000Z
There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.
Top quark physics in hadron collisions
Wolfgang Wagner
2007-08-03T23:59:59.000Z
The top quark is the heaviest elementary particle observed to date. Its large mass makes the top quark an ideal laboratory to test predictions of perturbation theory concerning heavy quark production at hadron colliders. The top quark is also a powerful probe for new phenomena beyond the Standard Model of particle physics. In addition, the top quark mass is a crucial parameter for scrutinizing the Standard Model in electroweak precision tests and for predicting the mass of the yet unobserved Higgs boson. Ten years after the discovery of the top quark at the Fermilab Tevatron top quark physics has entered an era where detailed measurements of top quark properties are undertaken. In this review article an introduction to the phenomenology of top quark production in hadron collisions is given, the lessons learned in Tevatron Run I are summarized, and first Run II results are discussed. A brief outlook to the possibilities of top quark research a the Large Hadron Collider, currently under construction at CERN, is included.
Gribov gap equation at finite temperature
Fabrizio Canfora; Pablo Pais; Patricio Salgado-Rebolledo
2014-06-05T23:59:59.000Z
In this paper the Gribov gap equation at finite temperature is analyzed. The solutions of the gap equation (which depend explicitly on the temperature) determine the structure of the gluon propagator within the semi-classical Gribov approach. The present analysis is consistent with the standard confinement scenario for low temperatures, while for high enough temperatures, deconfinement takes place and a free gluon propagator is obtained. It also suggests the presence of the so-called semi-quark-gluon-plasma phase in between the confined and quark-gluon plasma phases.
Light quark masses using domain wall fermions
Tom Blum; Amarjit Soni; Matthew Wingate
1998-09-10T23:59:59.000Z
We compute the one-loop self-energy correction to the massive domain wall quark propagator. Combining this calculation with simulations at several gauge couplings, we estimate the strange quark mass in the continuum limit. The perturbative one-loop mass renormalization is comparable to that for Wilson quarks and considerably smaller than that for Kogut-Susskind quarks. Also, scaling violations appear mild in comparison to other errors at present. Given their good chiral behavior and these features, domain wall quarks are attractive for evaluating the light quark masses. Our preliminary quenched result is m_s(2 GeV) = 82(15) MeV in the ${\\bar{MS}}$ scheme.
Quark Nuggets as Baryonic Dark Matter
Jan-e Alam; Sibaji Raha; Bikash Sinha
1997-04-23T23:59:59.000Z
The cosmic first order phase transition from quarks to hadrons, occurring a few microseconds after the Big Bang, would lead to the formation of quark nuggets which would be stable on a cosmological time scale, if the associated baryon number is larger than a critical value. We examine the possibility that these surviving quark nuggets may not only be viable candidates for cold dark matter but even close the universe.
Infrared Gluon and Ghost Propagators from Lattice QCD. Results from large asymmetric lattices
O. Oliveira; P. J. Silva
2006-11-15T23:59:59.000Z
We report on the infrared limit of the quenched lattice Landau gauge gluon and ghost propagators as well as the strong coupling constant computed from large asymmetric lattices. The infrared lattice propagators are compared with the pure power law solutions from Dyson-Schwinger equations (DSE). For the gluon propagator, the lattice data is compatible with the DSE solution. The preferred measured gluon exponent being $\\sim 0.52$, favouring a null zero momentum propagator. The lattice ghost propagator shows finite volume effects and, for the volumes considered, the propagator does not follow a pure power law. Furthermore, the strong coupling constant is computed and its infrared behaviour investigated.
Power-like corrections and the determination of the gluon distribution
F. Hautmann
2006-10-06T23:59:59.000Z
Power-suppressed corrections to parton evolution may affect the theoretical accuracy of current determinations of parton distributions. We study the role of multigluon-exchange terms in the extraction of the gluon distribution for the Large Hadron Collider (LHC). Working in the high-energy approximation, we analyze multi-gluon contributions in powers of 1/Q^2. We find a moderate, negative correction to the structure function's derivative d F_2 / d \\ln Q^2, characterized by a slow fall-off in the region of low to medium Q^2 relevant for determinations of the gluon at small momentum fractions.
Charmonium absorption and charmed hadron production in hadronic reactions
Liu, Wei
2005-02-17T23:59:59.000Z
for understanding charm production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC), where a quark-gluon plasma is expected to be formed during the initial hot dense stage....
Energy Blog | Department of Energy
Broader source: Energy.gov (indexed) [DOE]
3, 2010 Geek-Up12.03.2010: Halomonadaceae Bacteria and the Return of Quark Gluon Plasma The toxic element arsenic sustains growth of a bacteria instead of phosphorus and...
Partonic coalescence in relativistic heavy ion collisions
Greco, V.; Ko, Che Ming; Levai, P.
2003-01-01T23:59:59.000Z
Using a covariant coalescence model, we study hadron production in relativistic heavy ion collisions from both soft partons in the quark-gluon plasma and hard partons in minijets. Including transverse flow of soft partons and independent...
QGP viscosity at RHIC and the LHC - a 2012 status report
Huichao Song
2012-11-26T23:59:59.000Z
In this article, we briefly review the recent progress related to extracting the quark-gluon plasma (QGP) specific shear viscosity from the flow data measured at Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC).
Viscosity and jet quenching from holographic model
Yi-hong Gao; Wei-shui Xu; Ding-fang Zeng
2007-09-23T23:59:59.000Z
We consider the backreaction of the fundamental flavor degrees of freedom on the AdS$_5$-Schwarz background, and calculate their contributions to the shear viscosity and jet-quenching parameter of the thermal quark-gluon plasma.
Giovanni Raciti, in memoriam. NUCLEAR REACTIONS
Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University
) forma- tion of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive Electronic address: carlosbertulani@tamu-commmerce.edu C. Thermonuclear cross sections 22 IX. Reactions
XLV International Winter Meeting on Nuclear Physics BORMIO, Italy, January 14-21, 2007
Paris-Sud XI, UniversitÃ© de
XLV International Winter Meeting on Nuclear Physics BORMIO, Italy, January 14-21, 2007 The ALICE transition of nuclear matter from a hadron gas to a new state of matter, the Quark Gluon Plasma (QGP
Comments on two papers by Kapusta and Wong
P. Aurenche; R. Baier; T. Becherrawy; Y. Gabellini; F. Gelis; T. Grandou; M. Le Bellac; B. Pire; D. Schiff; H. Zaraket
2000-09-06T23:59:59.000Z
We critically examine recently published results on the thermal production of massive vector bosons in a quark-gluon plasma. We claim the production rate is a collinear safe observable.
antibaryons: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
HG HEP - Phenomenology (arXiv) Summary: We study quark-gluon plasma (QGP) and hadronic gas (HG) models of the central fireball presumed to be the source of abundantly produced...
Top Quark Physics at the CDF Experiment
Bernd Stelzer; for the CDF Collaboration
2010-07-21T23:59:59.000Z
Fermilab's Tevatron accelerator is recently performing at record luminosities that enables a program systematically addressing the physics of top quarks. The CDF collaboration has analyzed up to 5/fb of proton anti-proton collisions from the Tevatron at a center of mass energy of 1.96 TeV. The large datasets available allow to push top quark measurements to higher and higher precision and have lead to the recent observation of electroweak single top quark production at the Tevatron. This article reviews recent results on top quark physics from the CDF experiment.
Single Top Quarks at the Tevatron
A. P. Heinson
2008-09-05T23:59:59.000Z
After many years searching for electroweak production of top quarks, the Tevatron collider experiments have now moved from obtaining first evidence for single top quark production to an impressive array of measurements that test the standard model in several directions. This paper describes measurements of the single top quark cross sections, limits set on the CKM matrix element |Vtb|, searches for production of single top quarks produced via flavor-changing neutral currents and from heavy W-prime and H+ boson resonances, and studies of anomalous Wtb couplings. It concludes with projections for future expected significance as the analyzed datasets grow.
Jet substructures of boosted polarized top quarks
Yoshio Kitadono; Hsiang-nan Li
2014-09-05T23:59:59.000Z
We study jet substructures of a boosted polarized top quark, which undergoes the semileptonic decay $t\\to b\\ell\
Top Quark Production Asymmetries AFBt and AFBl
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Berger, Edmond L.; Cao, Qing-Hong; Chen, Chuan-Ren; Yu, Jiang-Hao; Zhang, Hao
2012-02-01T23:59:59.000Z
A large forward-backward asymmetry is seen in both the top quark rapidity distribution AFBt and in the rapidity distribution of charged leptons AFBl from top quarks produced at the Tevatron. We study the kinematic and dynamic aspects of the relationship of the two observables arising from the spin correlation between the charged lepton and the top quark with different polarization states. We emphasize the value of both measurements, and we conclude that a new physics model which produces more right-handed than left-handed top quarks is favored by the present data.
Top quark mass and properties at the Tevatron
J. -F. Arguin; for the CDF; D0 Collaborations
2005-07-29T23:59:59.000Z
We present recent analyses of top quark properties performed at Run II of the Tevatron. Measurements of the top quark mass, branching ratios and W boson helicity inside top quark decays are covered.
Collective perspective on advances in Dyson-Schwinger Equation QCD
Adnan Bashir; Lei Chang; Ian C. Cloet; Bruno El-Bennich; Yu-xin Liu; Craig D. Roberts; Peter C. Tandy
2012-01-16T23:59:59.000Z
We survey contemporary studies of hadrons and strongly interacting quarks using QCD's Dyson-Schwinger equations, addressing: aspects of confinement and dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and transition form factors, from small- to large-Q^2; parton distribution functions; the physics of hadrons containing one or more heavy quarks; and properties of the quark gluon plasma.
Quark Masses: An Environmental Impact Statement
Robert L. Jaffe; Alejandro Jenkins; Itamar Kimchi
2009-04-03T23:59:59.000Z
We investigate worlds that lie on a slice through the parameter space of the Standard Model over which quark masses vary. We allow as many as three quarks to participate in nuclei, while fixing the mass of the electron and the average mass of the lightest baryon flavor multiplet. We classify as "congenial" worlds that satisfy the environmental constraint that the quark masses allow for stable nuclei with charges one, six, and eight, making organic chemistry possible. Whether a congenial world actually produces observers depends on a multitude of historical contingencies, beginning with primordial nucleosynthesis, which we do not explore. Such constraints may be independently superimposed on our results. Environmental constraints such as the ones we study may be combined with information about the a priori distribution of quark masses over the landscape of possible universes to determine whether the measured values of the quark masses are determined environmentally, but our analysis is independent of such an anthropic approach. We estimate baryon masses as functions of quark masses and nuclear masses as functions of baryon masses. We check for the stability of nuclei against fission, strong particle emission, and weak nucleon emission. For two light quarks with charges 2/3 and -1/3, we find a band of congeniality roughly 29 MeV wide in their mass difference. We also find another, less robust region of congeniality with one light, charge -1/3 quark, and two heavier, approximately degenerate charge -1/3 and 2/3 quarks. No other assignment of light quark charges yields congenial worlds with two baryons participating in nuclei. We identify and discuss the region in quark-mass space where nuclei would be made from three or more baryon species.
Triangular flow in heavy ion collisions in a multiphase transport model
Xu, Jun; Ko, Che Ming.
2011-01-01T23:59:59.000Z
(RHIC) have provided important information on the properties of produced quark-gluon plasma (QGP) [1?4]. In particular, the large elliptic flow observed in experiments has led to the conclusion that the produced quark-gluon plasma is strongly...,10]. With the large parton scattering cross section, the transport model is also able to describe the hexadecupole flow measured at RHIC [11]. More recently, the importance of the triangular flow, which originates from fluctuations in the initial collision...
J/Psi suppression in ultrarelativistic nuclear collisions
Zhang, B.; Ko, Che Ming; Li, Ba; Lin, ZW; Sa, BW.
2000-01-01T23:59:59.000Z
- though all these signals have been observed in heavy ion collisions at CERN SPS, alternative explanations without in- voking the formation of the quark-gluon plasma have also been proposed. As the QGP is expected to be produced at RHIC... experiments at the Relativistic Heavy Ion Collider ~RHIC!, which allows collisions at much high energies than those available previously, are expected to provide a better oppor- tunity to create the quark-gluon plasma and to study its prop- erties. Since...
Comment on ``Success of collinear expansion in the calculation of induced gluon emission''
P. Aurenche; B. G. Zakharov; H. Zaraket
2008-06-01T23:59:59.000Z
We show that the arguments against our recent paper on the failure of the collinear expansion in the calculation of the induced gluon emission raised by X.N. Wang are either incorrect or irrelevant.
Numerical evaluation of multi-gluon amplitudes for High Energy Factorization
Bury, M
2015-01-01T23:59:59.000Z
We present a program to evaluate tree-level multi-gluon amplitudes with up to two of them off-shell. Furthermore, it evaluates squared amplitudes summed over colors and helicities for up to six external gluons. It employs both analytic expressions, obtained via BCFW recursion, and numerical BCFW recursion. It has been validated numerically with the help of an independent program employing numerical Dyson-Schwinger recursion.
Running alpha(s) from Landau-gauge gluon and ghost correlations
A. Sternbeck; E. -M. Ilgenfritz; K. Maltman; M. Müller-Preussker; L. von Smekal; A. G. Williams
2007-10-16T23:59:59.000Z
We estimate the running coupling constant of the strong interactions within the nonperturbative framework of lattice QCD in Landau gauge. Our calculation is based on the ghost-gluon vertex which in the particular case of Landau gauge allows for a definition of alpha(s) in a MOM scheme solely in terms of the gluon and ghost dressing functions. As a first step we investigate the zero and two-flavour case and report here on preliminary results.
Top quark physics expectations at the LHC
Andrei Gaponenko; for the ATLAS Collaboration; for the CMS Collaboration
2008-10-22T23:59:59.000Z
The top quark will be produced copiously at the LHC. This will make both detailed physics studies and the use of top quark decays for detector calibration possible. This talk reviews plans and prospects for top physics activities in the ATLAS and CMS experiments.
Heavy quark thermodynamics in full QCD
Konstantin Petrov; RBC-Bielefeld Collaboration
2007-01-22T23:59:59.000Z
We analyze the large-distance behaviour of static quark-anti-quark pair correlations in QCD. The singlet free energy is calculated and the entropy contribution to it is identified allowing us to calculate the excess internal energy. The free energy has a sharp drop in the critical region, leading to sharp peaks in both excess entropy and internal energy.
Light-Quark Decays in Heavy Hadrons
Faller, Sven
2015-01-01T23:59:59.000Z
We consider weak decays of heavy hadrons (bottom and charmed) where the heavy quark acts as a spectator. Theses decays are heavily phase-space suppressed but may become experimentally accessible in the near future. These decays are interesting as a QCD laboratory to study the behaviour of the light quarks in the colour-background field of the heavy spectator.
Static quark free energies at finite temperature
Z. Fodor; A. Jakovac; S. D. Katz; K. K. Szabo
2007-10-22T23:59:59.000Z
We determine the static quark free energies around the transition temperature using 2+1 flavors of staggered fermions. Simulations are carried out on N_t=4,6,8 and 10 lattices using physical quark masses. The free energies extracted from Polyakov-loop correlators are extrapolated to the continuum limit.
The Chandrasekhar limit for quark stars
Shibaji Banerjee; Sanjay K. Ghosh; Sibaji Raha
2000-01-14T23:59:59.000Z
The Chandrasekhar limit for quark stars is evaluated from simple energy balance relations, as proposed by Landau for white dwarfs or neutron stars. It has been found that the limit for quark stars depends on, in addition to the fundamental constants, the Bag constant.
Review of Top Quark Physics Results
Kehoe, R.; Narain, M.; Kumar, A.; ,
2007-12-01T23:59:59.000Z
As the heaviest known fundamental particle, the top quark has taken a central role in the study of fundamental interactions. Production of top quarks in pairs provides an important probe of strong interactions. The top quark mass is a key fundamental parameter which places a valuable constraint on the Higgs boson mass and electroweak symmetry breaking. Observations of the relative rates and kinematics of top quark final states constrain potential new physics. In many cases, the tests available with study of the top quark are both critical and unique. Large increases in data samples from the Fermilab Tevatron have been coupled with major improvements in experimental techniques to produce many new precision measurements of the top quark. The first direct evidence for electroweak production of top quarks has been obtained, with a resulting direct determination of V{sub tb}. Several of the properties of the top quark have been measured. Progress has also been made in obtaining improved limits on potential anomalous production and decay mechanisms. This review presents an overview of recent theoretical and experimental developments in this field. We also provide a brief discussion of the implications for further efforts.
Recent advances in heavy quark theory
Wise, M. [California Institute of Technology, Pasadena, CA (United States)
1997-01-01T23:59:59.000Z
Some recent developments in heavy quark theory are reviewed. Particular emphasis is given to inclusive weak decays of hadrons containing a b quark. The isospin violating hadronic decay D{sub s}* {yields} D{sub s}{sup pi}{sup 0} is also discussed.
Tevatron Top-Quark Combinations and World Top-Quark Mass Combination
Reinhild Yvonne Peters; on behalf of the ATLAS; CDF; CMS; D0 collaborations
2014-11-04T23:59:59.000Z
Almost 20 years after its discovery, the top quark is still an interesting particle, undergoing precise investigation of its properties. For many years, the Tevatron proton antiproton collider at Fermilab was the only place to study top quarks in detail, while with the recent start of the LHC proton proton collider a top quark factory has opened. An important ingredient for the full understanding of the top quark is the combination of measurements from the individual experiments. In particular, the Tevaton combinations of single top-quark cross sections, the ttbar production cross section, the W helicity in top-quark decays as well as the Tevatron and the world combination of the top-quark mass are discussed.
M. Bishai
2002-12-13T23:59:59.000Z
Heavy quark production cross-sections, correlations and polarizations have been measured at the Collider Detector at Fermilab (CDF) using 118 pb{sup -1} of data collected from the 1992 to 1995 Run I of the Fermilab Tevatron. There is still disagreement between theoretical predictions of bottom and charm hadro-production cross-sections and the Run I results. The observed transverse momentum spectrum of the prompt J/{psi} production polarization is still not understood. Run II of the Tevatron began in July of 2001 and the CDF Run II detector [11] has collected 70 pb{sup -1} of physics quality data since January 2002. Large statistics of onia states have been collected. Exclusive B meson decay modes have been reconstructed and the SVT level 2 displaced track trigger has produced large samples of D mesons. The prompt charm and b {yields} cX fractions in both charmonium and D meson samples have been measured. Run II is now poised to greatly enhance the knowledge of heavy quark production dynamics well beyond the reach of the Run I detector.
Hard quark-quark scattering with exclusive reactions
Barton, D.S.; Bunce, G.M.; Carroll, A.S.; Makdisi, Y.I.; Baller, B.; Blazey, G.C.; Courant, H.; Heller, K.J.; Heppelmann, S.; Marshak, M.L.
1984-07-19T23:59:59.000Z
We have begun a program designed to study hard quark-quark scattering with exclusive reactions, focusing on quasi-elastic two-body reactions with all possible quark flavor exchanges. Examples are ..pi../sup -/p ..-->.. ..pi../sup -/p, rho/sup -/p, ..pi../sup +/..delta../sup -/, K/sup +/..sigma../sup -/, or K..lambda... Of the two-body exclusives, only elastic scattering had been measured at such large t previous to our experiment. By comparing the relative importance of different final states, the energy dependence of the production ratios of these states, the prominence of resonances such as rho/sup -/ over background in this region, and measuring polarizations where accessible, we have collected a large body of data on hard scattering in a completely new domain. Previously, essential all short distance QCD tests have been for inclusive processes. We have taken data with both negative and positive incident beam at 10 GeV/c on a hydrogen target and will present the first results, for ..pi../sup -/p ..-->.. ..pi../sup -/p and rho/sup -/p at THETA/sub cm/ = 90/sup 0/, -t = 9 GeV/sup 2//c/sup 2/. The apparatus consists of a magnetic spectrometer, with Cerenkov particle identification, which selects stable charged particles (protons in this case) at high momentum near 90/sup 0/ in the center-of-mass. A large aperture array of PWCs observes the recoil particle or charged decay products. Cross sections are extremely low, approximately a 1 nb/(GeV/c)/sup 2/ for elastic scattering. We will report on a sample of more than 1000 ..pi../sup -/p elastic events, and on rho/sup -/p, where the rho/sup -/ decay distribution was observed. We find a surprisingly large rho/sup -/p cross section in this large momentum transfer region, with rho/sup -/p about half the elastic cross section, and a striking spin alignment of the rho/sup -/.
The QCD spectrum with three quark flavors
Claude Bernard; Tom Burch; Thomas A. DeGrand; Saumen Datta; Carleton DeTar; Steven Gottlieb; Urs M. Heller; Kostas Orginos; Robert Sugar; Doug Toussaint
2001-05-29T23:59:59.000Z
We present results from a lattice hadron spectrum calculation using three flavors of dynamical quarks - two light and one strange, and quenched simulations for comparison. These simulations were done using a one-loop Symanzik improved gauge action and an improved Kogut-Susskind quark action. The lattice spacings, and hence also the physical volumes, were tuned to be the same in all the runs to better expose differences due to flavor number. Lattice spacings were tuned using the static quark potential, so as a byproduct we obtain updated results for the effect of sea quarks on the static quark potential. We find indications that the full QCD meson spectrum is in better agreement with experiment than the quenched spectrum. For the 0++ (a0) meson we see a coupling to two pseudoscalar mesons, or a meson decay on the lattice.
Kaczmarek, O
2005-01-01T23:59:59.000Z
We analyze the change in free energy, internal energy and entropy due to the presence of a heavy quark anti-quark pair in a QCD heat bath. The internal energies and entropies are introduced as intensive observables calculated through thermal derivatives of the QCD partition function containing additional static color sources. The quark anti-quark internal energy and, in particular, the entropy clearly signal the phase change from quark confinement below and deconfinement above the transition and both observables are introduced such that they survive the continuum limit. The intermediate and large distance behavior of the energies reflect string breaking and color screening phenomena. This is used to characterize the energies which are needed to dissolve heavy quarkonium states in a thermal medium. Our discussion supports recent findings which suggest that parts of the quarkonium systems may survive the phase transition and dissolve only at higher temperatures.
Asymptotic freedom and quarks confinement treated through Thompson's approach
Claudio Nassif; J. A. Helayel-Neto; P. R. Silva
2007-08-02T23:59:59.000Z
In this work,we firstly use Thompson's renormalization group method to treat QCD-vacuum behavior close to the regime of asymptotic freedom. QCD-vacuum behaves effectively like a "paramagnetic system" of a classical theory in the sense that virtual color charges (gluons) emerge in it as spin effect of a paramagnetic material when a magnetic field aligns their microscopic magnetic dipoles. Making a classical analogy with the paramagnetism of Landau's theory,we are able to introduce a kind of Landau effective action without temperature and phase transition for simply representing QCD-vacuum behavior at higher energies as magnetization of a paramagnetic material in the presence of a magnetic field H. This reasoning allows us to use Thompson's heuristic approach in order to extract an "effective susceptibility" ($\\chi>0$) of QCD-vacuum. It depends on logarithmic of energy scale u to investigate hadronic matter. Consequently,we are able to get an "effective magnetic permeability" ($\\mu>1$) of such a "paramagnetic vacuum". As QCD-vacuum must obey Lorentz invariance,the attainment of $\\mu>1$ must simply require that the "effective electrical permissivity" is $\\epsilon<1$,in such a way that $\\mu\\epsilon=1$ (c^2=1).This leads to the antiscreening effect,where the asymptotic freedom takes place.On the other hand,quarks cofinement,a subject which is not treatable by perturbative calculations,is worked by the present approach. We apply the method to study this subject in order to obtain the string constant,which is in agreement with experimental results.
Messner, R. [Stanford Univ., CA (United States)
1997-01-01T23:59:59.000Z
This report covers preliminary measurements from SLD on heavy quark production at the Z{sup 0}, using 150,000 hadronic Z{sup 0} decays accumulated during the 1993-1995 runs. A measurement of R{sub b} with a lifetime double tag is presented. The high electron beam polarization of the SLC is employed in the direct measurement of the parity-violating parameters A{sub b} and A{sub c} by use of the left-right forward-backward asymmetry. The lifetimes of B{sup +} and B{sup 0} mesons have been measured by two analyses. The first identifies semileptonic decays of B mesons with high (p,p{sub t}) leptons; the second analysis isolates a sample of B meson decays with a two-dimensional impact parameter tag and reconstructs the decay length and charge using a topological vertex reconstruction method.
Top Quark Pair Production in Early CMS Data
Kao, Shih-Chuan
2011-01-01T23:59:59.000Z
23 2.13 top decay . . . . . . . . . . . . .of the Top Quark . . . . . . . . . . . . . . . . . . . . .20 Top Production in Hadron
Top Quark Physics at the ILC: Methods and Meanings
Zack Sullivan
2009-03-06T23:59:59.000Z
The physics case for studying top-quark physics at the International Linear Collider is well established. This summary places in context the top-quark physics goals, examines the current state-of-the art in understanding of the top-quark mass, and identifies some areas in which the study of the top-quark mass enhances our understanding of new techniques.
Singlet Free Energies of a Static Quark-Antiquark Pair
Konstantin Petrov
2004-09-01T23:59:59.000Z
We study the singlet part of the free energy of a static quark anti-quark pair at finite temperature in three flavor QCD with degenerate quark masses using $N_{\\tau}=4$ and 6 lattices with Asqtad staggered fermion action. We look at thermodynamics of the system around phase transition and study its scaling with lattice spacing and quark masses.
Newtonian gravity, red shift, confinement, asymptotic freedom and quarks oscillations
G. Quznetsov
2008-10-18T23:59:59.000Z
Quarks oscillations give the Newtonian gravity law, the red shift, the confinement and the asymptotic freedom.
Discovery of single top quark production
Gillberg, Dag
2009-05-01T23:59:59.000Z
The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking - the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies. Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years. This thesis presents the first discovery of single top quark production. An analysis is performed using 2.3 fb{sup -1} of data recorded by the D0 detector at the Fermilab Tevatron Collider at centre-of-mass energy {radical}s = 1.96 TeV. Boosted decision trees are used to isolate the single top signal from background, and the single top cross section is measured to be {sigma}(p{bar p} {yields} tb + X, tqb + X) = 3.74{sub -0.74}{sup +0.95} pb. Using the same analysis, a measurement of the amplitude of the CKM matrix element V{sub tb}, governing how top and b quarks mix, is also performed. The measurement yields: |V{sub tb}|f{sub 1}{sup L}| = 1.05{sub -0.12}{sup +0.13}, where f{sub 1}{sup L} is the left-handed Wtb coupling. The separation of signal from background is improved by combining the boosted decision trees with two other multivariate techniques. A new cross section measurement is performed, and the significance for the excess over the predicted background exceeds 5 standard deviations.
Top Quark Forward-Backward Asymmetry
Kingman Cheung; Wai-Yee Keung; Tzu-Chiang Yuan
2009-11-17T23:59:59.000Z
The recent forward-backward asymmetry recorded by the CDF Collaboration for the top and anti-top quark pair production indicates more than $2\\sigma$ deviation from the Standard Model prediction, while its total production cross section remains consistent. We propose a $W'$ boson that couples to down and top quarks. We identify the parameter space that can give rise a large enough forward-backward asymmetry without producing too many top and anti-top quark pairs. Other models presented erstwhile in the literature that can produce such effects are also discussed.
Top quark properties from the Tevatron
Klute, Markus; /MIT, LNS
2006-05-01T23:59:59.000Z
This report describes latest measurements and studies of top quark properties from the Tevatron in Run II with an integrated luminosity of up to 750 pb{sup -1}. Due to its large mass of about 172 GeV/c{sup 2}, the top quark provides a unique environment for tests of the Standard Model and is believed to yield sensitivity to new physics beyond the Standard Model. With data samples of close to 1 fb{sup -1} the CDF and D0 collaborations at the Tevatron enter a new area of precision top quark measurements.
A. M. Green; C. Michael; J. E. Paton
1992-09-15T23:59:59.000Z
Four-quark potentials for $SU(2)$ are evaluated in the static limit with the quenched approximation -- using a lattice of $16^3\\times 32$ and $\\beta=2.4$. The four quarks are restricted to the corners of rectangles with sides upto seven lattice spacings long. The results are analysed in terms of a strategy based on interquark two-body potentials -- as advocated earlier by the authors. This shows that a standard two-body approach overestimates the four-quark binding energy by upto a factor of about three for the largest rectangles.
Stability of plasma oscillations in hot gluonic matter
Kobes, R.; Kunstatter, G.
1988-07-25T23:59:59.000Z
It is argued that the high-temperature gluon-plasma damping constants previously calculated by use of the background-field method and the Vilkovisky-DeWitt effective action do not have a physical interpretation since they are not derived from correlation functions relevant to linear-response theory. A correct application of the gauge- and parametrization-independent formalism does not affect the plasmon frequency, but yields the following modified results for the longitudinal and transverse damping constants: ..gamma../sub L/ = ..gamma../sub T/ = -(9/32..pi..)g/sup 2/NT. .AE
Heavy Quark Anti-Quark Free Energy and the Renormalized Polyakov Loop
Kaczmarek, O; Petreczky, P; Zantow, F
2002-01-01T23:59:59.000Z
We calculate the colour averaged and colour singlet free energies of static quark anti-quark sources placed in a thermal gluonic heat bath. We discuss the renormalization of these free energies using the short distance properties of the zero temperature heavy quark potential. This leads to the definition of the renormalized Polyakov loop as an order parameter for the deconfinement phase transition of the SU(3) gauge theory which is well behaved in the continuum limit.
Recent Results of Top Quark Physics from the Tevatron
R. Y. Peters; on behalf of the D0; CDF collaborations
2015-07-09T23:59:59.000Z
Twenty years after its discovery in 1995 by the CDF and D0 collaborations at the Tevatron proton-antiproton collider at Fermilab, the top quark still undergoes intensive studies at the Tevatron and the LHC at CERN. In this article, recent top quark physics results from CDF and D0 are reported. In particular, measurements of single top quark and double top quark production, the ttbar forward-backward asymmetry and the top quark mass are discussed.
Quenched hadron spectroscopy with improved staggered quark action
MILC Collaboration; Claude Bernard; Tom Blum; Thomas A. DeGrand; Carleton DeTar; Steven Gottlieb; Urs M. Heller; James Hetrick; Craig McNeile; K. Rummukainen; Bob Sugar; Doug Toussaint
1997-12-11T23:59:59.000Z
We investigate light hadron spectroscopy with an improved quenched staggered quark action. We compare the results obtained with an improved gauge plus an improved quark action, an improved gauge plus standard quark action, and the standard gauge plus standard quark action. Most of the improvement in the spectroscopy results is due to the improved gauge sector. However, the improved quark action substantially reduces violations of Lorentz invariance, as evidenced by the meson dispersion relations.
Abbiendi, G; Åkesson, P F; Alexander, G; Allison, J; Amaral, P; Anagnostou, G; Anderson, K J; Arcelli, S; Asai, S; Axen, D A; Azuelos, Georges; Bailey, I; Barberio, E; Barillari, T; Barlow, R J; Batley, J Richard; Bechtle, P; Behnke, T; Bell, K W; Bell, P J; Bella, G; Bellerive, A; Benelli, G; Bethke, Siegfried; Biebel, O; Boeriu, O; Bock, P; Boutemeur, M; Braibant, S; Brigliadori, L; Brown, R M; Büsser, K; Burckhart, H J; Campana, S; Carnegie, R K; Caron, B; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Ciocca, C; Csilling, Akos; Cuffiani, M; Dado, S; de Roeck, A; De Wolf, E A; Desch, Klaus; Dienes, B; Donkers, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Etzion, E; Fabbri, Franco Luigi; Feld, L; Ferrari, P; Fiedler, F; Fleck, I; Ford, M; Frey, A; Fürtjes, A; Gagnon, P; Gary, J W; Gaycken, G; Geich-Gimbel, C; Giacomelli, G; Giacomelli, P; Giunta, M; Goldberg, J; Gross, E; Grunhaus, Jacob; Gruwé, M; Günther, P O; Sen-Gupta, A; Hajdu, C; Hamann, M; Hanson, G G; Harel, A; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Hensel, C; Herten, G; Heuer, R D; Hill, J C; Hoffman, K; Horváth, D; Igo-Kemenes, P; Ishii, K; Jeremie, H; Jovanovic, P; Junk, T R; Kanaya, N; Kanzaki, J; Karlen, Dean A; Kawagoe, K; Kawamoto, T; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Klein, K; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Komamiya, S; Kormos, L L; Kramer, T; Krieger, P; Von Krogh, J; Krüger, K; Kühl, T; Kupper, M; Lafferty, G D; Landsman, Hagar Yaël; Lanske, D; Layter, J G; Lellouch, D; Letts, J; Levinson, L; Lillich, J; Lloyd, S L; Loebinger, F K; Lü, J; Ludwig, A; Ludwig, J; MacPherson, A; Mader, W; Marcellini, S; Martin, A J; Masetti, G; Mashimo, T; Mättig, P; McDonald, W J; McKenna, J A; McMahon, T J; McPherson, R A; Meijers, F; Menges, W; Merritt, F S; Mes, H; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Moed, S; Mohr, W; Mori, T; Mutter, A; Nagai, K; Nakamura, I; Nanjo, H; Neal, H A; Nisius, R; O'Neale, S W; Oh, A; Okpara, A N; Oreglia, M J; Orito, S; Pahl, C; Pásztor, G; Pater, J R; Pilcher, J E; Pinfold, J L; Plane, D E; Poli, B; Polok, J; Pooth, O; Przybycien, M B; Quadt, A; Rabbertz, K; Rembser, C; Renkel, P; Roney, J M; Rosati, S; Rozen, Y; Runge, K; Sachs, K; Saeki, T; Sarkisyan-Grinbaum, E; Schaile, A D; Schaile, O; Scharff-Hansen, P; Schieck, J; Schörner-Sadenius, T; Schröder, M; Schumacher, M; Schwick, C; Scott, W G; Seuster, R; Shears, T G; Shen, B C; Sherwood, P; Skuja, A; Smith, A M; Sobie, R J; Söldner-Rembold, S; Spanó, F; Stahl, A; Stephens, K; Strom, D; Ströhmer, R; Tarem, S; Tasevsky, M; Teuscher, R; Thomson, M A; Torrence, E; Toya, D; Tran, P; Trigger, I; Trócsányi, Z L; Tsur, E; Turner-Watson, M F; Ueda, I; Ujvári, B; Vollmer, C F; Vannerem, P; Vertesi, R; Verzocchi, M; Voss, H; Vossebeld, Joost Herman; Waller, D; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wengler, T; Wermes, N; Wetterling, D; Wilson, G W; Wilson, J A; Wolf, G; Wyatt, T R; Yamashita, S; Zer-Zion, D; Zivkovic, L
2004-01-01T23:59:59.000Z
We present the first experimental results based on the jet boost algorithm, a technique to select unbiased samples of gluon jets in e+e- annihilations, i.e. gluon jets free of biases introduced by event selection or jet finding criteria. Our results are derived from hadronic Z0 decays observed with the OPAL detector at the LEP e+e- collider at CERN. First, we test the boost algorithm through studies with Herwig Monte Carlo events and find that it provides accurate measurements of the charged particle multiplicity distributions of unbiased gluon jets for jet energies larger than about 5 GeV, and of the jet particle energy spectra (fragmentation functions) for jet energies larger than about 14 GeV. Second, we apply the boost algorithm to our data to derive unbiased measurements of the gluon jet multiplicity distribution for energies between about 5 and 18 GeV, and of the gluon jet fragmentation function at 14 and 18 GeV. In conjunction with our earlier results at 40 GeV, we then test QCD calculations for the en...
Commissioning ATLAS and CMS with top quarks
B. S. Acharya; F. Cavallari; G. Corcella; R. Di Sipio; G. Petrucciani
2008-05-25T23:59:59.000Z
The large ttbar production cross-section at the LHC suggests the use of top quark decays to calibrate several critical parts of the detectors, such as the trigger system, the jet energy scale and b-tagging.
Kong, Kyoungchul; Lee, Hye-Sung; Park, Myeonghun
2014-04-01T23:59:59.000Z
We suggest top quark decays as a venue to search for light dark force carriers. The top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6sigma deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t-->bW+Z's. This is the same as the dominant top quark decay (t-->bW) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.
Theory of top quark production and decay
Kuehn, J.H. [Universitaet Karlsruhe (Germany)
1997-01-01T23:59:59.000Z
Direct and indirect information on the top quark mass and its decay modes is reviewed. The theory of top production in hadron- and electron-positron-colliders is presented.
Mass inequality for the quark propagator
Dean Lee; Richard Thomson
2005-06-09T23:59:59.000Z
We show that for any gauge-fixing scheme with positive semi-definite functional integral measure, the inverse correlation length of the quark propagator is bounded below by one-half the pion mass.
Relativistic harmonic oscillator model for quark stars
Vishnu M. Bannur
2008-10-06T23:59:59.000Z
The relativistic harmonic oscillator (RHO) model of hadrons is used to study quark stars. The mass-radius relationship is obtained and compared with bag model of quark star, using Tolman-Oppenheimer-Volkoff equation. In this model, the outward degenerate pressure due to discrete Landau levels and Landau degeneracy balances the inward gravitational pressure. Where as in bag model the degenerate pressure is due to the standard continuum levels which balances the combined inward pressure due to gravitation and bag pressure. So in RHO model, the confinement effect is included in the degenerate pressure. We found a qualitative similarity, but quantitative differences in mass-radius relationship of quark stars in these two models. Masses and radii are relatively larger and the central energy densities, required for stable quark stars, are lower in RHO model than that of bag model.
Evidence for production of single top quarks
Abazov, V.M.; /Dubna, JINR; Abbott, B.; /Oklahoma U.; Abolins, M.; /Michigan State U.; Acharya, B.S.; /Tata Inst.; Adams, M.; /Illinois U., Chicago; Adams, T.; /Florida State U.; Aguilo, E.; /Simon Fraser U.; Ahn, S.H.; /Korea U., KODEL; Ahsan, M.; /Kansas State U.; Alexeev, G.D.; /Dubna, JINR; Alkhazov, G.; /St. Petersburg, INP /Michigan U.
2008-03-01T23:59:59.000Z
We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p{bar p} collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top quark partner that is always produced from strong coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top quark production has been searched for in ever larger datasets. In this analysis, we select events from a 0.9 fb{sup -1} dataset that have an electron or muon and missing transverse energy from the decay of a W boson from the top quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and t{bar t} events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top quark production of {sigma}(p{bar p} {yields} tb + X, tqb + X) = 4.7 {+-} 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find |V{sub tb}f{sub 1}{sup L}| = 1.31{sub -0.21}{sup +0.25}, where f{sub 1}{sup L} is a generic vector coupling. This model-independent measurement translates into 0.68 < |V{sub tb}| {le} 1 at the 95% C.L. in the standard model.
Single top quark production at the Tevatron
Schwienhorst, Reinhard; /Michigan State U.
2008-05-01T23:59:59.000Z
The Tevatron experiments D0 and CDF have found evidence for single top quark production, based on datasets between 0.9 fb{sup -1} and 2.2 fb{sup -1}. Several different multivariate techniques are used to extract the single top quark signal out of the large backgrounds. The cross section measurements are also used to provide the first direct measurement of the CKM matrix element |V{sub tb}|.
Charmonium with three flavors of synamical quarks
Massimo Di Pierro et al.
2003-12-23T23:59:59.000Z
We present a calculation of the charmonium spectrum with three flavors of dynamical staggered quarks from gauge configurations that were generated by the MILC collaboration. We use the Fermilab action for the valence charm quarks. Our calculation of the spin-averaged 1P-1S and 2S-1S splittings yields a determination of the strong coupling, with {alpha}{sub {ovr MS}}(M{sub Z}) = 0.119(4).
Shear viscosity of the quark matter
Masaharu Iwasaki; Hiromasa Ohnishi; Takahiko Fukutome
2007-05-14T23:59:59.000Z
We discuss shear viscosity of the quark matter by using Kubo formula. The shear viscosity is calculated in the framework of the quasi-particle RPA for the Nambu-Jona-Lasinio model. We obtain a formula that the shear viscosity is expressed by the quadratic form of the quark spectral function in the chiral symmetric phase. The magnitude of the shear viscosity is discussed assuming the Breit-Wigner type for the spectral function.
Running heavy-quark masses in DIS
S. Alekhin; S. -O. Moch
2011-07-03T23:59:59.000Z
We report on determinations of the running mass for charm quarks from deep-inelastic scattering reactions. The method provides complementary information on this fundamental parameter from hadronic processes with space-like kinematics. The obtained values are consistent with but systematically lower than the world average as published by the PDG. We also address the consequences of the running mass scheme for heavy-quark parton distributions in global fits to deep-inelastic scattering data.
Magnetism and superconductivity in quark matter
T. Tatsumi; E. Nakano; K. Nawa
2005-06-01T23:59:59.000Z
Magnetic properties of quark matter and its relation to the microscopic origin of the magnetic field observed in compact stars are studied. Spontaneous spin polarization appears in high-density region due to the Fock exchange term, which may provide a scenario for the behaviors of magnetars. On the other hand, quark matter becomes unstable to form spin density wave in the moderate density region, where restoration of chiral symmetry plays an important role. Coexistence of magnetism and color superconductivity is also discussed.
Free magnetized knots of parity-violating deconfined matter in heavy-ion collisions
M. N. Chernodub
2010-02-07T23:59:59.000Z
We show that the local parity violation in the quark-gluon plasma supports existence of free (meta)stable knots of deconfined hot quark matter stabilized by superstrong magnetic fields. The magnetic field in the knots resembles the spheromak plasma state of the magnetic confinement approach to nuclear fusion. The size of the knot is quantized, being inversely proportional to the chiral conductivity of the quark-gluon plasma. The parity symmetry is broken inside the knot. Particles produced in the decays of the knots have unusual azimuthal distribution and specific flavor content. We argue that these knots may be created in noncentral heavy-ion collisions.
Free magnetized knots of parity-violating deconfined matter in heavy-ion collisions
Chernodub, M N
2010-01-01T23:59:59.000Z
We show that the local parity violation in the quark-gluon plasma supports existence of free (meta)stable knots of deconfined hot quark matter stabilized by superstrong magnetic fields. The magnetic field in the knots resembles the spheromak plasma state of the magnetic confinement approach to nuclear fusion. The size of the knot is quantized, being inversely proportional to the chiral conductivity of the quark-gluon plasma. The parity symmetry is broken inside the knot. Particles produced in the decays of the knots have unusual azimuthal distribution and specific flavor content. We argue that these knots may be created in noncentral heavy-ion collisions.
Heavy-light quarks interactions in QCD vacuum
Mirzayusuf Musakhanov
2015-03-20T23:59:59.000Z
QCD vacuum instantons induce very strong interactions between light quarks, which generate large dynamical light quark mass M for initially almost massless quarks and can bound these quarks to produce almost massless pions in accordance with the spontaneous breaking of chiral symmetry (S\\chiSB). On the other hand, the QCD vacuum instantons generate heavy-light quark interactions terms, which are responsible for the effects of S\\chiSB in a heavy-light quark system. Summing the re-scattering series that lead to the total light quark propagator and making few further steps, we get the fermionized representation of low-frequencies light quark determinant in the presence of the quark sources, which is relevant for our problems. The next important step in the line of this strategy is to derive the equation and calculate the heavy quark propagator in the instanton media and in the presence of light quarks. This one provide finally the heavy and N_f light quarks interaction term. As an example, we derive heavy quark-light mesons interaction term for the N_f=2 case. If we take the average instanton size \\rho=0.35 fm, and average inter-instanton distance R=0.856 fm from our previous estimates, we obtain at LO on 1/N_c expansion dynamical light quark mass M = 570 MeV and instanton media contribution to heavy quark mass \\Delta M=148 MeV. These factors define the coupling between heavy and light quarks and, certainly, between heavy quarks and light mesons. We will apply this approach to heavy quark and heavy-light quark systems.
Xie, Si
We present a measurement of the ratio of the tt? production cross section via gluon-gluon fusion to the total tt? production cross section in pp? collisions at ?s=1.96??TeV at the Tevatron. Using a data sample with an ...
Equilibrium configurations for quark-diquark stars and the problem of Her X-1 mass
J. E. Horvath; J. A. de Freitas Pacheco
1996-11-20T23:59:59.000Z
We report new calculations of the physical properties of a quark-diquark plasma. A vacuum contribution is taken into account and is responsible for the appearance of a stable state at zero pressure and at a baryon density of about 2.2 times the nuclear matter density in this model. The resulting equation of state was used to integrate numerically the Tolman-Oppenheimer-Volkoff equations. The mass-radius relationship has been derived from a series of equilibrium configurations constituted by a mixture of quarks and diquarks. These stellar models, which are representative of a whole class, may be helpful to understand the possible compactness of the X-ray source Her X-1 and related objects.
Phase transition from hadronic matter to quark matter
P. Wang; A. W. Thomas; A. G. Williams
2007-04-03T23:59:59.000Z
We study the phase transition from nuclear matter to quark matter within the SU(3) quark mean field model and NJL model. The SU(3) quark mean field model is used to give the equation of state for nuclear matter, while the equation of state for color superconducting quark matter is calculated within the NJL model. It is found that at low temperature, the phase transition from nuclear to color superconducting quark matter will take place when the density is of order 2.5$\\rho_0$ - 5$\\rho_0$. At zero density, the quark phase will appear when the temperature is larger than about 148 MeV. The phase transition from nuclear matter to quark matter is always first order, whereas the transition between color superconducting quark matter and normal quark matter is second order.
Thermophoretic Flow in Relativistic Heavy-Ion Collisions
Thoma, M H
2001-01-01T23:59:59.000Z
If a quark-gluon plasma is formed in relativistic heavy-ion collisions, there might be a mixed phase of quarks and gluons and hadronic clusters when the critical temperature is reached in the expansion of the fireball. If there is a temperature gradient in the fireball, the hadronic clusters, embedded in the heat bath of quarks and gluons, are subjected to a thermophoretic force. It is shown that even for small temperature gradients and short lifetimes of the mixed phase thermophoresis leads to a strong flow.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:Energy: Grid Integration Redefining What's Possible for RenewableSpeedingBiomassPPPOPetroleum38 (1996) A213-A225. Printed in the UK4 Plasma
Measurements of top quark properties at the Tevatron collider
Margaroli, Fabrizio
2011-05-01T23:59:59.000Z
The discovery of the top quark in 1995 opened a whole new sector of investigation of the Standard Model; today top quark physics remains a key priority of the Tevatron program. Some of the measurements of top quark properties, for example its mass, will be a long-standing legacy. The recent evidence of an anomalously large charge asymmetry in top quark events suggests that new physics could couple preferably with top quarks. I will summarize this long chapter of particle physics history and discuss the road the top quark is highlighting for the LHC program.
Universal Mass Texture, CP violation and Quark-Lepton Complementarity
Canales, F Gonzalez; Barranco, J
2010-01-01T23:59:59.000Z
Recent measurements of the neutrino and quark mixing angles satisfy the empirical relations called quark-lepton complementarity. These empirical relations suggests the existence of a correlation between the mixing matrices of leptons and quarks. In this work, we examine the possibility that this correlation between the mixing angles of quarks and leptons originates in the similar hierarchy of quarks and charged lepton masses and the seesaw mechanism type I, that gives mass to the Majorana neutrinos. We asssume that the similar mass hierarchies of charged lepton and quark masses allows us to represent all the mass matrices of Dirac fermions in terms of a two zeroes Fritzsch texture.
Universal mass matrix for quarks and leptons and CP violation
Barranco, J.; Gonzalez Canales, F.; Mondragon, A. [Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut), Am Muehlenberg 1, D-14476 Golm (Germany); Instituto de Fisica, Universidad Nacional Autonoma de Mexico, 04510, Mexico D.F. (Mexico)
2010-10-01T23:59:59.000Z
The measurements of the neutrino and quark mixing angles satisfy the empirical relations called quark-lepton complementarity. These empirical relations suggest the existence of a correlation between the mixing matrices of leptons and quarks. In this work, we examine the possibility that this correlation between the mixing angles of quarks and leptons originates in the similar hierarchy of quarks and charged lepton masses and the seesaw mechanism type I, that gives mass to the Majorana neutrinos. We assume that the similar mass hierarchies of charged lepton and quark masses allows us to represent all the mass matrices of Dirac fermions in terms of a universal form with four texture zeroes.
Chang-Hwan Lee; Ismail Zahed
2014-03-07T23:59:59.000Z
We discuss the general features of the electromagnetic radiation from a thermal hadronic gas as constrained by chiral symmetry. The medium effects on the electromagnetic spectral functions and the partial restoration of chiral symmetry are quantified in terms of the pion densities. The results are compared with the electromagnetic radiation from a strongly interacting quark-gluon plasma in terms of the leading gluon condensate operators. We use the spectral functions as constrained by the emission rates to estimate the electric conductivity, the light flavor susceptibility and diffusion constant across the transition from the correlated hadronic gas to a strongly interacting quark-gluon plasma.
Color superconductivity and dense quark matter
Massimo Mannarelli
2008-12-26T23:59:59.000Z
The properties of cold and dense quark matter have been the subject of extensive investigation, especially in the last decade. Unfortunately, we still lack of a complete understanding of the properties of matter in these conditions. One possibility is that quark matter is in a color superconducting phase which is characterized by the formation of a diquark condensate. We review some of the basic concepts of color superconductivity and some of the aspects of this phase of matter which are relevant for compact stars. Since quarks have color, flavor as well as spin degrees of freedom many different color superconducting phases can be realized. At asymptotic densities QCD predicts that the color flavor locked phase is favored. At lower densities where the QCD coupling constant is large, perturbative methods cannot be applied and one has to rely on some effective model, eventually trying to constrain such a model with experimental observations. The picture is complicated by the requirement that matter in the interior of compact stars is in weak equilibrium and neutral. These conditions and the (possible) large value of the strange quark mass conspire to separate the Fermi momenta of quarks with different flavors, rendering homogenous superconducting phases unstable. One of the aims of this presentation is to introduce non-experts in the field to some of the basic ideas of color superconductivity and to some of its open problems.
Infrared behavior of the gluon and ghost propagators in Yang-Mills theories
M. Capri; D. Dudal; J. Gracey; V. Lemes; R. Sobreiro; S. P. Sorella; R. Thibes; H. Verschelde
2006-10-29T23:59:59.000Z
We provide a short discussion of the dimension two condensate and its influence on the infrared behaviour of the gluon propagator in the Landau gauge. Simultaneously, we pay attention to the issue of Gribov copies in the Landau gauge. We also briefly discuss a local, gauge invariant non-Abelian action with mass parameter, constructed from the dimension 2 operator $F_{\\mu\
Compass Results on Gluon Polarisation from High pT hadron pairs
L. Silva; for the COMPASS Collaboration
2010-10-13T23:59:59.000Z
One of the goals of the COMPASS experiment is the determination of the gluon polarisation \\Delta G/G, for a deep understanding of the spin structure of the nucleon. In DIS the gluon polarisation can be measured via the Photon-Gluon-Fusion (PGF) process, identified by open charm production or by selecting high p_T hadron pairs in the final state. The data used for this work were collected by the COMPASS experiment during the years 2002-2004, using a 160 GeV naturally polarised positive muon beam scattering on a polarised nucleon target. A new preliminary result of the gluon polarisation \\Delta G/G from high p_T hadron pairs in events with Q^2>1 (GeV/c)^2 is presented. In order to extract \\Delta G/G, this analysis takes into account the leading process \\gamma q contribution together with the PGF and QCD Compton processes. A new weighted method based on a neural network approach is used. A preliminary \\Delta G/G result for events from quasi-real photoproduction (Q^2<1 (GeV/c)^2) is also presented.
Lattice QCD Thermodynamics with Physical Quark Masses
R. A. Soltz; C. DeTar; F. Karsch; Swagato Mukherjee; P. Vranas
2015-02-08T23:59:59.000Z
Over the past few years new physics methods and algorithms as well as the latest supercomputers have enabled the study of the QCD thermodynamic phase transition using lattice gauge theory numerical simulations with unprecedented control over systematic errors. This is largely a consequence of the ability to perform continuum extrapolations with physical quark masses. Here we review recent progress in lattice QCD thermodynamics, focussing mainly on results that benefit from the use of physical quark masses: the crossover temperature, the equation of state, and fluctuations of the quark number susceptibilities. In addition, we place a special emphasis on calculations that are directly relevant to the study of relativistic heavy ion collisions at RHIC and the LHC.
The heavy top quark and supersymmetry
Hall, L.J. [Lawrence Berkeley Lab., CA (United States); [Univ. of California, Berkeley, CA (United States)
1997-01-01T23:59:59.000Z
Three aspects of supersymmetric theories are discussed: electroweak symmetry breaking, the issues of flavor, and gauge unification. The heavy top quark plays an important, sometimes dominant, role in each case. Additional symmetries lead to extensions of the Standard Model which can provide an understanding for many of the outstanding problems of particle physics. A broken supersymmetric extension of spacetime allows electroweak symmetry breaking to follow from the dynamics of the heavy top quark; an extension of isospin provides a constrained framework for understanding the pattern of quark and lepton masses; and a grand unified extension of the Standard Model gauge group provides an elegant understanding of the gauge quantum numbers of the components of a generation. Experimental signatures for each of these additional symmetries are discussed.
Short distance physics with heavy quark potentials
Zantow, F; Karsch, Frithjof; Petreczky, P
2002-01-01T23:59:59.000Z
We present lattice studies of heavy quark potentials in the quenched approximation of QCD at finite temperatures. Both, the color singlet and color averaged potentials are calculated. While the potentials are well known at large distances, we give a detailed analysis of their short distance behavior (from 0.015 fm to 1 fm) near the critical temperature. At these distances we expect that the T-dependent potentials go over into the zero temperature potential. Indeed, we find evidences that the temperature influence gets suppressed and the potentials starts to become a unique function of the underlying distance scale. We use this feature to normalize the heavy quark potentials at short distances and extract the free energy of the quark system in a gluonic heat bath.
Dressed Quark Mass Dependence of Pion and Kaon Form Factors
Y. Ninomiya; W. Bentz; I. C. Cloët
2015-01-27T23:59:59.000Z
The structure of hadrons is described well by the Nambu--Jona-Lasinio (NJL) model, which is a chiral effective quark theory of QCD. In this work we explore the electromagnetic structure of the pion and kaon using the three-flavor NJL model, including effects of confinement and a pion cloud at the quark level. In the calculation there is only one free parameter, which we take as the dressed light quark ($u$ and $d$) mass. In the regime where the dressed light quark mass is approximately $0.25\\,$GeV, we find that the calculated values of the kaon decay constant, current quark masses, and quark condensates are consistent with experiment and QCD based analyses. We also investigate the dressed light quark mass dependence of the pion and kaon electromagnetic form factors, where comparison with empirical data and QCD predictions also favors a dressed light quark mass near $0.25\\,$GeV.
Bulk viscosity in nuclear and quark matter: A short review
Hui Dong; Nan Su; Qun Wang
2007-03-05T23:59:59.000Z
The history and recent progresses in the study of bulk viscosity in nuclear and quark matter are reviewed. The constraints from baryon number conservation and electric neutrality in quark matter on particle densities and fluid velocity divergences are discussed.
QCD evolution of (un)polarized gluon TMDPDFs and the Higgs $q_T$-distribution
Miguel G. Echevarria; Tomas Kasemets; Piet J. Mulders; Cristian Pisano
2015-02-18T23:59:59.000Z
We provide the proper definition of all the leading-twist (un)polarized gluon transverse momentum dependent parton distribution functions (TMDPDFs), by considering the Higgs boson transverse momentum distribution in hadron-hadron collisions and deriving the factorization theorem in terms of them. We show that the evolution of all the (un)polarized gluon TMDPDFs is driven by a universal evolution kernel, which can be resummed up to next-to-next-to-leading-logarithmic accuracy. Considering the proper definition of gluon TMDPDFs, we perform an explicit next-to-leading-order calculation of the unpolarized ($f_1^g$), linearly polarized ($h_1^{\\perp g}$) and helicity ($g_{1L}^g$) gluon TMDPDFs, and show that, as expected, they are free from rapidity divergences. As a byproduct, we obtain the Wilson coefficients of the refactorization of these TMDPDFs at large transverse momentum. In particular, the coefficient of $g_{1L}^g$, which has never been calculated before, constitutes a new and necessary ingredient for a reliable phenomenological extraction of this quantity, for instance at RHIC or the future AFTER@LHC or Electron-Ion Collider. The coefficients of $f_1^g$ and $h_1^{\\perp g}$ have never been calculated in the present formalism, although they could be obtained by carefully collecting and recasting previous results in the new TMD formalism. We apply these results to analyze the contribution of linearly polarized gluons at different scales, relevant, for instance, for the inclusive production of the Higgs boson and the $C$-even pseudoscalar bottomonium state $\\eta_{b}$. Applying our resummation scheme we finally provide predictions for the Higgs boson $q_T$-distribution at the LHC.
Joint resummation for heavy quark production.
Banfi, Andrea; Laenen, Eric
ar X iv :h ep -p h/ 05 10 14 9v 1 1 2 O ct 2 00 5 February 2, 2008 4:14 WSPC/INSTRUCTION FILE jr International Journal of Modern Physics A c© World Scientific Publishing Company JOINT RESUMMATION FOR HEAVY QUARK PRODUCTION ANDREA BANFI Cavendish... hadroproduction, at next-to-leading logarithmic accuracy. We exhibit their dependence on the production channel and the color configurations, and compare these distributions to eachother and to NLO. Keywords: Resummation; heavy quark production. 1. Joint threshold...
Top Quark Mass Measurements at the Tevatron
Zhenyu Ye; for CDF; D0 collaborations
2011-07-22T23:59:59.000Z
We report the latest results on the top-quark mass and on the top-antitop mass difference from the CDF and D0 collaborations using data collected at the Fermilab Tevatron $p\\bar{p}$ collider at $\\sqrt{s}=1.96$ TeV. We discuss general issues in top-quark mass measurements and present new results from direct measurements and from top-pair production cross-section. We also report new results on the top-antitop mass difference.
Top Quark Mass Measurements at the Tevatron
Ye, Zhenyu; /Fermilab
2011-07-01T23:59:59.000Z
We report the latest results on the top-quark mass and on the top-antitop mass difference from the CDF and D0 collaborations using data collected at the Fermilab Tevatron p{bar p} collider at {radical}s = 1.96 TeV. We discuss general issues in top-quark mass measurements and present new results from direct measurements and from top-pair production cross-section. We also report new results on the top-antitop mass difference.
Quark mass thresholds in QCD thermodynamics
M. Laine; Y. Schroder
2006-05-05T23:59:59.000Z
We discuss radiative corrections to how quark mass thresholds are crossed, as a function of the temperature, in basic thermodynamic observables such as the pressure, the energy and entropy densities, and the heat capacity of high temperature QCD. The indication from leading order that the charm quark plays a visible role at surprisingly low temperatures, is confirmed. We also sketch a way to obtain phenomenological estimates relevant for generic expansion rate computations at temperatures between the QCD and electroweak scales, pointing out where improvements over the current knowledge are particularly welcome.
New lattice action for heavy quarks
Oktay, Mehmet B.; Kronfeld, Andreas S. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States) and School of Mathematics, Trinity College, Dublin 2 (Ireland); Theoretical Physics Department, Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)
2008-07-01T23:59:59.000Z
We extend the Fermilab method for heavy quarks to include interactions of dimensions 6 and 7 in the action. There are, in general, many new interactions, but we carry out the calculations needed to match the lattice action to continuum QCD at the tree level, finding six nonzero couplings. Using the heavy-quark theory of cutoff effects, we estimate how large the remaining discretization errors are. We find that our tree-level matching, augmented with one-loop matching of the dimension-5 interactions, can bring these errors below 1%, at currently available lattice spacings.
Correlations of chiral condensates and quark number densities with static quark sources
Kay Huebner
2007-09-10T23:59:59.000Z
We investigate correlation functions of the Polyakov loop and static meson/diquark systems with the chiral condensate and the quark number density at finite temperature. In particular the latter observable can give insight in the mechanism of screening and string breaking at finite temperature. We use for our analysis gauge field configurations generated in 2+1 flavor QCD with an improved staggered fermion action with almost physical light quark masses and a physical value of the strange quark mass on lattices with temporal extent Nt=4 and 6.
Review of recent top-quark LHC combinations
Giorgio Cortiana; on behalf of the ATLAS; CMS collaborations within the TOPLHCWG
2014-11-27T23:59:59.000Z
A review of recent combinations of top-quark measurements performed at the LHC, by the ATLAS and CMS collaborations, is provided. The typical uncertainty categorisations, and their assumed correlation patterns are presented, together with the results of the combinations of the top-quark pair and single top-quark production cross sections, the top-quark mass, as well as of the $W$ boson polarisation and the charge asymmetry in $t\\bar t$ events.
Light quark spectrum with improved gauge and fermion actions
MILC Collaboration; Claude Bernard; Tom DeGrand; Carleton DeTar; Steven Gottlieb; Urs M. Heller; Jim Hetrick; Craig McNeile; Kari Rummukainen; Bob Sugar; Doug Toussaint; Matthew Wingate
1997-11-08T23:59:59.000Z
We report on a study of the light quark spectrum using an improved gauge action and both Kogut-Susskind and Naik quark actions. We have studied six different lattice spacings, corresponding to plaquette couplings ranging from 6.8 to 7.9, with five to six quark masses per coupling. We compare the two quark actions in terms of the spectrum and restoration of flavor symmetry. We also compare these results with those from the conventional action.
Systems of two heavy quarks with effective field theories
Nora Brambilla
2006-09-22T23:59:59.000Z
I discuss results and applications of QCD nonrelativistic effective field theories for systems with two heavy quarks.
TOP QUARK PHYSICS AT THE NLC CARL R. SCHMIDT
Schmidt, Carl
TOP QUARK PHYSICS AT THE NLC CARL R. SCHMIDT Santa Cruz Institute for Particle Physics University) is an excellent tool for studying the properties of the top quark. In this talk I review some of the theory of top, is an ideal tool for studying the properties of the top quark. The event environment in e + e \\Gamma
Anomalous radial transport in tokamak edge plasma
Bodi, Vasudeva Raghavendra Kowsik
2010-01-01T23:59:59.000Z
Transport in tokamak plasma . . . . . . . . . . . . . . .Numerical simulations of tokamak plasma . . . . . . . . .of blobs in tokamak edge plasmas . . . . . . . . . . . . . .
Plasma PhysicsPlasma Physics Atoms Beams and PlasmasAtoms Beams and Plasmas
Strathclyde, University of
of plasma research and understanding their dynamics is cutting edge topic in physics Small instabilities
Motley, R.W.; Glanz, J.
1982-10-25T23:59:59.000Z
A device is described for coupling RF power (a plasma sweeper) from RF power introducing means to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the RF power introducing means. Means are described for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.
Strange quark momentum fraction from overlap fermion
Mingyang Sun; Yi-Bo Yang; Keh-Fei Liu; Ming Gong
2015-03-10T23:59:59.000Z
We present a calculation of $_s$ for the strange quark in the nucleon. We also report the ratio of the strange $$ to that of $u/d$ in the disconnected insertion which will be useful in constraining the global fit of parton distribution functions at small $x$. We adopt overlap fermion action on $2 + 1$ flavor domain-wall fermion configurations on the $24^3 \\times 64$ lattice with a light sea quark mass which corresponds to $m_{\\pi}=330$ MeV. Smeared grid $Z_3$ sources are deployed to calculate the nucleon propagator with low-mode substitution. Even-odd grid sources and time-dilution technique with stochastic noises are used to calculate the high mode contribution to the quark loop. Low mode averaging (LMA) for the quark loop is applied to reduce the statistical error of the disconnected insertion calculation. We find the ratio $_s/_{u/d}^{\\mathrm{DI}}= 0.78(3)$ in this study.
Strange quark momentum fraction from overlap fermion
Sun, Mingyang; Liu, Keh-Fei; Gong, Ming
2015-01-01T23:59:59.000Z
We present a calculation of $\\langle x \\rangle_s$ for the strange quark in the nucleon. We also report the ratio of the strange $\\langle x \\rangle$ to that of $u/d$ in the disconnected insertion which will be useful in constraining the global fit of parton distribution functions at small $x$. We adopt overlap fermion action on $2 + 1$ flavor domain-wall fermion configurations on the $24^3 \\times 64$ lattice with a light sea quark mass which corresponds to $m_{\\pi}=330$ MeV. Smeared grid $Z_3$ sources are deployed to calculate the nucleon propagator with low-mode substitution. Even-odd grid sources and time-dilution technique with stochastic noises are used to calculate the high mode contribution to the quark loop. Low mode averaging (LMA) for the quark loop is applied to reduce the statistical error of the disconnected insertion calculation. We find the ratio $\\langle x \\rangle_s/\\langle x \\rangle_{u/d}^{\\mathrm{DI}}= 0.78(3)$ in this study.
Strange Quark Matter and Compact Stars
Fridolin Weber
2004-09-27T23:59:59.000Z
Astrophysicists distinguish between three different types of compact stars. These are white dwarfs, neutron stars, and black holes. The former contain matter in one of the densest forms found in the Universe which, together with the unprecedented progress in observational astronomy, make such stars superb astrophysical laboratories for a broad range of most striking physical phenomena. These range from nuclear processes on the stellar surface to processes in electron degenerate matter at subnuclear densities to boson condensates and the existence of new states of baryonic matter--like color superconducting quark matter--at supernuclear densities. More than that, according to the strange matter hypothesis strange quark matter could be more stable than nuclear matter, in which case neutron stars should be largely composed of pure quark matter possibly enveloped in thin nuclear crusts. Another remarkable implication of the hypothesis is the possible existence of a new class of white dwarfs. This article aims at giving an overview of all these striking physical possibilities, with an emphasis on the astrophysical phenomenology of strange quark matter. Possible observational signatures associated with the theoretically proposed states of matter inside compact stars are discussed as well. They will provide most valuable information about the phase diagram of superdense nuclear matter at high baryon number density but low temperature, which is not accessible to relativistic heavy ion collision experiments.
Top quark property measurements at the LHC
Richard Hawkings
2014-10-29T23:59:59.000Z
Measurements of top quark properties performed at the Large Hadron Collider are reviewed, with a particular emphasis on top-pair charge asymmetries, spin correlations and polarization measurements performed by the ATLAS and CMS collaborations. The measurements are generally in good agreement with predictions from next-to-leading-order QCD calculations, and no deviations from Standard Model expectations have been seen.
From Quarks to Real Life Fred Jegerlehner
Röder, Beate
) Atom 10-8 10-4 e.m., QED Nucleus, Electron 10-12 10-3 nuclear power Hadrons: Proton, Neutron 10 photon with charged particles, electrons,.... e+ e- Abelian theory U(1) phase transformations F only, color singlets, color unobservable! « Confinement QUARKS are permanently confined inside HADRONS
Unusual condensates in quark and atomic systems
B. Kerbikov
2005-10-31T23:59:59.000Z
In these lectures we discuss condensates which are formed in quark matter when it is squeezed and in a gas of fermionic atoms when it is cooled. The behavior of these two seemingly very different systems reveals striking similarities. In particular, in both systems the Bose-Einstein condensate to Bardeen--Cooper-Schrieffer (BEC-BCS) crossover takes place.
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya; N. Ukita; T. Umeda
2010-05-11T23:59:59.000Z
Screenings of the quark-gluon plasma in electric and magnetic sectors are studied on the basis of generalized Polyakov-line correlation functions in lattice QCD simulations with two flavors of improved Wilson quarks. Using the Euclidean-time reflection ($\\R$) and the charge conjugation ($\\Ca$), electric and magnetic screening masses are extracted in a gauge invariant manner. Long distance behavior of the standard Polyakov-line correlation in the quark-gluon plasma is found to be dictated by the magnetic screening. Also, ratio of the two screening masses agrees with that obtained from the dimensionally-reduced effective field theory and the ${\\cal N}=4$ supersymmetric Yang-Mills theory.
Bottomonium production at root s(NN)=200 GeV and root s(NN)=5.5 TeV
Grandchamp, L.; Lumpkins, S.; Sun, D.; van Hees, H.; Rapp, Ralf.
2006-01-01T23:59:59.000Z
Properties of bottomonia (Upsilon,chi(b), and Upsilon ') in the quark-gluon plasma (QGP) are investigated by assessing inelastic reaction rates and their interplay with open-bottom states (b quarks or B mesons) and color screening. The latter leads...
Susceptibilities with multi-quark interactions in PNJL model
Abhijit Bhattacharyya; Paramita Deb; Anirban Lahiri; Rajarshi Ray
2011-01-06T23:59:59.000Z
We have investigated the fluctuations and the higher order susceptibilities of quark number, isospin number, electric charge and strangeness at vanishing chemical potential for 2+1 flavor Polyakov loop extended Nambu--Jona-Lasinio model. The calculations are performed for the bound effective potential in the quark sector requiring up to eight quark interaction terms. These have been contrasted to the lattice results which currently have somewhat heavier quarks in the light flavor sector. The results show sufficient qualitative agreement. For comparison we also present the results obtained with the conventional effective potential containing upto six quark interaction terms.
Valence quark distributions of the proton from maximum entropy approach
Rong Wang; Xurong Chen
2014-10-14T23:59:59.000Z
We present an attempt of maximum entropy principle to determine valence quark distributions in the proton at very low resolution scale $Q_0^2$. The initial three valence quark distributions are obtained with limited dynamical information from quark model and QCD theory. Valence quark distributions from this method are compared to the lepton deep inelastic scattering data, and the widely used CT10 and MSTW08 data sets. The obtained valence quark distributions are consistent with experimental observations and the latest global fits of PDFs. Maximum entropy method is expected to be particularly useful in the case where relatively little information from QCD calculation is given.
Valence quark distributions of the proton from maximum entropy approach
Wang, Rong
2014-01-01T23:59:59.000Z
We present an attempt of maximum entropy principle to determine valence quark distributions in the proton at very low resolution scale $Q_0^2$. The initial three valence quark distributions are obtained with limited dynamical information from quark model and QCD theory. Valence quark distributions from this method are compared to the lepton deep inelastic scattering data, and the widely used CT10 and MSTW08 data sets. The obtained valence quark distributions are consistent with experimental observations and the latest global fits of PDFs. Maximum entropy method is expected to be particularly useful in the case where relatively little information from QCD calculation is given.
The Absence of Plasma in "Spark Plasma Sintering"
Hulbert, Dustin M.
2008-01-01T23:59:59.000Z
investigations on the spark plasma sintering/synthesisinvestigations on the spark plasma sintering/synthesisenhancement in spark-plasma sintering: Impact of high
Top Quark Properties at the TeVatron
Yvonne Peters for the CDF; D0 Collaborations
2011-03-29T23:59:59.000Z
Discovered in 1995 by CDF and D0 at the Fermilab Tevatron collider, the top quark remains interesting to test the Standard Model. Having collected more than 7 fb$^{-1}$ of integrated luminosity with both experiments until today, several top quark properties have been measured with increasing precision, while other properties have been investigated for the first time. In this article recent measurements of top quark properties from CDF and D0 are presented, using between 1 fb$^{-1}$ and 4.8 fb$^{-1}$ of data. In particular, the measurement of the top quark mass, the top quark width, the top antitop mass difference, a check of the electric charge of the top quark, measurements of the top antitop quark spin correlation and W helicity as well as a search for charged Higgs bosons are discussed.
I. Bloch, DESY/Hamburg University - CIPANP, Puerto Rico 30.5.-03.06.'06 1Heavy Quarks at HERA Heavy, Puerto Rico 30.5.-03.06.'06 2Heavy Quarks at HERA HERA: ep collisions within H1 & ZEUS 920 GeV protons920/Hamburg University - CIPANP, Puerto Rico 30.5.-03.06.'06 3Heavy Quarks at HERA H1&ZEUS integrated Luminosity: 96