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.
Quark-Gluon Plasma: Present and Future
Tapan K. Nayak
2008-04-08T23:59:59.000Z
We review a sample of the experimental results from AGS to SPS and RHIC and their interpretations towards understanding of the Quark-Gluon Plasma. We discuss extrapolations of these results to the upcoming LHC experiments. Finally, we present the plans to probe the QCD critical point with an energy scan at RHIC and FAIR facilities.
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).
Quark Propagation in the Quark-Gluon Plasma
Xiangdong Li; Hu Li; C. M. Shakin; Qing Sun
2004-03-05T23:59:59.000Z
It has recently been suggested that the quark-gluon plasma formed in heavy-ion collisions behaves as a nearly ideal fluid. That behavior may be understood if the quark and antiquark mean-free- paths are very small in the system, leading to a "sticky molasses" description of the plasma, as advocated by the Stony Brook group. This behavior may be traced to the fact that there are relatively low-energy $q\\bar{q}$ resonance states in the plasma leading to very large scattering lengths for the quarks. These resonances have been found in lattice simulation of QCD using the maximum entropy method (MEM). We have used a chiral quark model, which provides a simple representation of effects due to instanton dynamics, to study the resonances obtained using the MEM scheme. In the present work we use our model to study the optical potential of a quark in the quark-gluon plasma and calculate the quark mean-free-path. Our results represent a specific example of the dynamics of the plasma as described by the Stony Brook group.
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...
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...
Dynamics of quark-gluon plasma from Field correlators
A. Di Giacomo; E. Meggiolaro; Yu. A. Simonov; A. I. Veselov
2005-12-22T23:59:59.000Z
It is argued that strong dynamics in the quark-gluon plasma and bound states of quarks and gluons is mostly due to nonperturbative effects described by field correlators. The emphasis in the paper is made on two explicit calculations of these effects from the first principles: one analytic using gluelump Green's functions and another using independent lattice data on correlators. The resulting hadron spectra are investigated in the range T_c MEM data. The possible role of these bound states in the thermodynamics of quark-gluon plasma is discussed.
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...
Tomography of the Quark-Gluon-Plasma by Charm Quarks
Taesoo Song; Hamza Berrehrah; Daniel Cabrera; Juan M. Torres-Rincon; Laura Tolos; Wolfgang Cassing; Elena Bratkovskaya
2015-07-02T23:59:59.000Z
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 sections calculated in an effective lagrangian approach with heavy-quark spin symmetry. Finally, the nuclear modification factor $\\rm R_{AA}$ and the elliptic flow $v_2$ of $D^0$ mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at $\\sqrt{s_{\\rm NN}}$ =200 GeV. We find that in the PHSD the energy loss of $D$ mesons at high $p_T$ can be dominantly attributed to partonic scattering while the actual shape of $\\rm R_{AA}$ versus $p_T$ reflects the heavy quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the $\\rm R_{AA}$ at low $p_T$ and enhances the $D$-meson elliptic flow $v_2$.
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.
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.
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
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\
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
2015-02-02T23:59:59.000Z
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.
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...
Leonard S. Kisslinger; Debasish Das
2015-05-12T23:59:59.000Z
This is a review of the Quantum Chrodynamics Cosmological Phase Transition, the Quark-Gluon Plasma, and the detection of the Quark-Gluon Plasma via RHIC(Relativistic Heavy Ion Collisions) production of heavy quark states using the mixed hybrid theory for the $\\Psi(2S)$ and $\\Upsilon(3S)$ states.
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.
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.
Heavy quark production from jet conversions in a quark-gluon plasma
Liu, W.; Fries, Rainer J.
2008-01-01T23:59:59.000Z
multiplied by a K factor. The heavy quarks can be produced from the annihilation process g + g? Q+ ?Q that converts a gluon jet and a thermal gluon to a pair of heavy quarks, and also through theCompton processesg(q)+Q? Q+ g(q) by transferring... averaging ?Y (p?)? for the elastic process Q+ g(q)? Q+ g(q) is defined in Refs. [11] and [17]. Using a fixed coupling constant ?s = 0.3 and masses mg = gT / ? 2 for thermal gluons and mq = gT / ? 6 for thermal quarks [18], we calculate the transport...
Photon production from a non-equilibrium quark-gluon plasma
Bhattacharya, Lusaka; Strickland, Michael
2015-01-01T23:59:59.000Z
We calculate leading-order medium photon yields from a quark-gluon plasma using (3+1)D anisotropic hydrodynamics. Non-equilibrium modifications of the photon rate is taken into account using a self-consistent modification of the particle distribution functions and the corresponding anisotropic hard-loop fermionic self-energies. We present predictions for the high-energy photon spectrum and photon elliptic flow as a function of transverse momentum, shear viscosity, and initial momentum-space anisotropy. Our findings indicate that high-energy photon production is sensitive to the assumed level of initial momentum-space anisotropy of the quark-gluon plasma. As a result, it may be possible to experimentally constrain the early-time momentum-space anisotropy of the quark-gluon plasma generated in relativistic heavy-ion collisions using high energy photon yields.
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.
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 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.
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...
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.
Equation of state of a quark-gluon plasma using the Cornell potential
Udayanandan, K. M.; Sethumadhavan, P.; Bannur, V. M. [Department of Physics, University of Calicut, Kerala 673 635 (India)
2007-10-15T23:59:59.000Z
The equation of state (EOS) of quark-gluon plasma (QGP) using the Cornell potential based on Mayer's cluster expansion is presented. The string constant and the strong coupling constant for QGP are calculated. The EOS developed could describe the lattice EOS for pure gauge, two-flavor and three-flavor QGP qualitatively.
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.
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.
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.
Equation of state of strongly coupled quark--gluon plasma -- Path integral Monte Carlo results
V. S. Filinov; M. Bonitz; Y. B. Ivanov; V. V. Skokov; P. R. Levashov; V. E. Fortov
2009-05-04T23:59:59.000Z
A strongly coupled plasma of quark and gluon quasiparticles at temperatures from $ 1.1 T_c$ to $3 T_c$ is studied by path integral Monte Carlo simulations. This method extends previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime. We present the equation of state and find good agreement with lattice results. Further, pair distribution functions and color correlation functions are computed indicating strong correlations and liquid-like behavior.
Event-by-event hydrodynamics: A better tool to study the Quark-Gluon plasma
Grassi, Frederique [Instituto de Fisica, Universidade de Sao Paulo (Brazil)
2013-03-25T23:59:59.000Z
Hydrodynamics has been established as a good tool to describe many data from relativistic heavyion collisions performed at RHIC and LHC. More recently, it has become clear that it is necessary to use event-by-event hydrodynamics (i.e. describe each collision individually using hydrodynamics), an approach first developed in Brazil. In this paper, I review which data require the use of event-by-event hydrodynamics and what more we may learn on the Quark-Gluon Plasma with this.
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...
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.
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.
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.
Jet-Triggered Photons from Back-Scattering Kinematics for Quark Gluon Plasma Tomography
Somnath De; Rainer J. Fries; Dinesh K. Srivastava
2014-10-11T23:59:59.000Z
High energy photons created from back-scattering of jets in quark gluon plasma are a valuable probe of the temperature of the plasma, and of the energy loss mechanism of quarks in the plasma. An unambiguous identification of these photons through single inclusive photon measurements and photon azimuthal anisotropies has so far been elusive. We estimate the spectra of back-scattering photons in coincidence with trigger jets for typical kinematic situations at the Large Hadron Collider and the BNL Relativistic Heavy Ion Collider. We find that the separation of back-scattering photons from other photon sources using trigger jets depends crucially on our ability to reliably estimate the initial trigger jet energy. We estimate that jet reconstruction techniques in heavy ion experiments need to be able to get to jet $R_{AA}\\gtrsim 0.7$ in central collisions for viable back-scattering signals.
Comparison of Models of Critical Opacity in the Quark-Gluon Plasma
Xiangdong Li; C. M. Shakin
2004-07-20T23:59:59.000Z
In this work we discuss two methods of calculation of quark propagation in the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model. The essential difference of these calculations is the treatment of deconfinement. A model of confinement is not included in the work of Gastineau, Blanquier and Aichelin [hep-ph/0404207], however, the meson states they consider are still bound for temperatures greater than the deconfinement temperature T_c. On the other hand, our model deals with unconfined quarks and includes a description of the q(bar)q resonances found in lattice QCD studies that make use of the maximum entropy method (MEM). We compare the q{bar)q cross sections calculated in these models.
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
Mannarelli, Massimo; Manuel, Cristina; Gonzalez-Solis, Sergi [Instituto de Ciencias del Espacio (IEEC/CSIC), Campus Universitat Autonoma de Barcelona, Facultat de Ciencies, Torre C5 E-08193 Bellaterra, Barcelona (Spain); Strickland, Michael [Department of Physics, Gettysburg College, Gettysburg, Pennsylvania 17325 (United States)
2010-04-01T23:59:59.000Z
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 tsunamilike distribution function. We find qualitative and semiquantitative agreement between the results obtained with the two methods.
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.
Speed of sound in quark gluon plasma with one loop correction in mean field potential
S. Somorendro Singh; R. Ramanathan
2015-05-14T23:59:59.000Z
We study thermodynamic properties and speed of sound in a free en- ergy evolution of quark-gluon plasma (QGP) with one loop correction factor in the mean-field potential. The values of the thermodynamic prop- erties like pressure, entropy and specific heat are calculated for a range of temperatures. The results agree with the recent lattice results. The speed of sound is found to be C2 s = 0.3 independent of parameters used in the loop correction which matches almost with lattice calculations.
Speed of sound in quark gluon plasma with one loop correction in mean field potential
Singh, S Somorendro
2015-01-01T23:59:59.000Z
We study thermodynamic properties and speed of sound in a free en- ergy evolution of quark-gluon plasma (QGP) with one loop correction factor in the mean-field potential. The values of the thermodynamic prop- erties like pressure, entropy and specific heat are calculated for a range of temperatures. The results agree with the recent lattice results. The speed of sound is found to be C2 s = 0.3 independent of parameters used in the loop correction which matches almost with lattice calculations.
Cavitation in a quark gluon plasma with finite chemical potential and several transport coefficients
S. M. Sanches Jr.; D. A. Fogaēa; F. S. Navarra; H. Marrochio
2015-08-14T23:59:59.000Z
We study the effects of a finite chemical potential on the occurrence of cavitation in a quark gluon plasma (QGP). We solve the evolution equations of second order viscous relativistic hydrodynamics using three different equations of state. The first one was derived in lattice QCD and represents QGP at zero chemical potential. It was previously used in the study of cavitation. The second equation of state also comes from lattice QCD and is a recent parametrization of the QGP at finite chemical potential. The third one is similar to the MIT equation of state with chemical potential and includes nonperturbative effects through the gluon condensates. We conclude that at finite chemical potential cavitation in the QGP occurs earlier than at zero chemical potential. We also consider transport coefficients from a holographic model of a non-conformal QGP at zero chemical potential. In this case cavitation does not occur.
Cavitation in a quark gluon plasma with finite chemical potential and several transport coefficients
Sanches, S M; Navarra, F S; Marrochio, H
2015-01-01T23:59:59.000Z
We study the effects of a finite chemical potential on the occurrence of cavitation in a quark gluon plasma (QGP). We solve the evolution equations of second order viscous relativistic hydrodynamics using three different equations of state. The first one was derived in lattice QCD and represents QGP at zero chemical potential. It was previously used in the study of cavitation. The second equation of state also comes from lattice QCD and is a recent parametrization of the QGP at finite chemical potential. The third one is similar to the MIT equation of state with chemical potential and includes nonperturbative effects through the gluon condensates. We conclude that at finite chemical potential cavitation in the QGP occurs earlier than at zero chemical potential. We also consider transport coefficients from a holographic model of a non-conformal QGP at zero chemical potential. In this case cavitation does not occur.
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
2015-05-04T23:59:59.000Z
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, $\\sigma_{el}$. Once the relaxation time is tuned to have a minimum value of $\\eta/s=1/4\\pi$ near the critical temperature $T_c$, one simultaneously predicts $\\sigma_{el}/T$ very close to recent lQCD data. More generally, we discuss why the ratio of $(\\eta/s)/(\\sigma_{el}/T)$ 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 $\\sim 20$ for $T \\rightarrow T_c$, while it goes down to a nearly flat behavior around $\\simeq 4$ for $T \\geq 4\\, T_c$. Therefore we in general predict a stronger T dependence of $\\sigma_{el}/T$ with respect to $\\eta/s$ that in a quasiparticle approach is constrained by lQCD thermodynamics. A conformal theory, instead, predicts a similar T dependence of $\\eta/s$ and $\\sigma_{el}/T$.
Energy loss, equilibration, and thermodynamics of a baryon rich strongly coupled quark-gluon plasma
Rougemont, Romulo; Finazzo, Stefano; Noronha, Jorge
2015-01-01T23:59:59.000Z
Lattice data for the QCD equation of state and the baryon susceptibility near the crossover phase transition (at zero baryon density) are used to determine the input parameters of a 5-dimensional Einstein-Maxwell-Dilaton holographic model that provides a consistent holographic framework to study both equilibrium and out-of-equilibrium properties of a hot and {\\it baryon rich} strongly coupled quark-gluon plasma (QGP). We compare our holographic equation of state computed at nonzero baryon chemical potential, $\\mu_B$, with recent lattice calculations and find quantitative agreement for the pressure and the speed of sound for $\\mu_B \\leq 400$ MeV. This holographic model is used to obtain holographic predictions for the temperature and $\\mu_B$ dependence of the drag force and the Langevin diffusion coefficients associated with heavy quark jet propagation as well as the jet quenching parameter $\\hat{q}$ and the shooting string energy loss of light quarks in the dense plasma. We find that the energy loss of heavy ...
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.
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)
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
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.
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...
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.
Scott Pratt
2012-01-13T23:59:59.000Z
In the canonical picture of the evolution of the quark-gluon plasma during a high-energy heavy-ion collision, quarks are produced in two waves. The first is during the first fm/c of the collision, when gluons thermalize into the QGP. After a roughly isentropic expansion that roughly conserves the number of quarks, a second wave ensues at hadronization, 5-10 fm/c into the collision. Since each hadron contains at least two quarks, the majority of quark production occurs at this later time. For each quark produced in a heavy-ion collision, an anti-quark of the same flavor is created at the same point in space-time. Charge balance functions identify, on a statistical basis, the location of balancing charges for a given hadron, and given the picture above one expects the distribution in relative rapidity of balancing charges to be characterized by two scales. After first demonstrating how charge balance functions can be created using any pair of hadronic states, it will be shown how one can identify and study both processes of quark production. By considering balance functions of several hadronic species, and by performing illustrative calculations, this class of measurement appears to hold the prospect of providing the field's most stringent insight into the chemical evolution of the QGP.
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...
Gert Aarts; Chris Allton; Seyong Kim; Maria Paola Lombardo; Mehmet B. Oktay; Sinead M. Ryan; D. K. Sinclair; Jon-Ivar Skullerud
2011-11-21T23:59:59.000Z
We study bottomonium spectral functions in the quark-gluon plasma in the Upsilon and eta_b channels, using lattice QCD simulations with two flavours of light quark on highly anisotropic lattices. The bottom quark is treated with nonrelativistic QCD (NRQCD). In the temperature range we consider, 0.42 MEM), used to construct the spectral functions, are discussed in some detail.
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
is adjusted to hydrodynamic simulations of semicentral Au-Au collisions at RHIC. To facilitate the applicability of the Langevin process, we focus on strange and charm quarks. Their interactions in the QGP are modeled using leading-order perturbative QCD...
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...
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.
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.
Quarkgluon 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 quarkgluon 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.
He, Yayun; Wang, Xin-Nian; Zhu, Yan
2015-01-01T23:59:59.000Z
A Linear Boltzmann Transport model within the perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions and angular distribution of reconstructed jets.
Rougemont, Romulo
2015-01-01T23:59:59.000Z
Five dimensional black hole solutions that describe the QCD crossover transition seen in (2+1)-flavor lattice QCD calculations at nonzero baryon densities are used to obtain predictions for the baryon susceptibility, baryon conductivity, baryon diffusion constant, and thermal conductivity of the strongly coupled quark-gluon plasma in the range of temperatures $T=130-300$ MeV and baryon chemical potentials $\\mu_B=0-400$ MeV. Diffusive transport is predicted to be already suppressed in this region of the QCD phase diagram in a way that is consistent with the existence of a critical end point at larger baryon densities.
Yayun He; Tan Luo; Xin-Nian Wang; Yan Zhu
2015-05-21T23:59:59.000Z
A Linear Boltzmann Transport model within perturbative QCD is developed for the study of parton propagation inside the quark-gluon plasma. Both leading partons and thermal recoil partons are tracked so that one can also study jet-induced medium excitations. In this study, we implement the complete set of elastic parton scattering processes and investigate elastic parton energy loss, transverse momentum broadening and their nontrivial energy and length dependence. We further investigate medium modifications of the jet shape and fragmentation functions of reconstructed jets. Contributions from thermal recoil partons are found to have significant influences on jet shape, fragmentation functions and angular distribution of reconstructed jets.
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
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.
Yannis Burnier; Dmitri E. Kharzeev; Jinfeng Liao; Ho-Ung Yee
2011-03-07T23:59:59.000Z
Chiral Magnetic Wave (CMW) is a gapless collective excitation of quark-gluon plasma in the presence of external magnetic field that stems from the interplay of Chiral Magnetic (CME) and Chiral Separation Effects (CSE); it is composed by the waves of the electric and chiral charge densities coupled by the axial anomaly. We consider CMW at finite baryon density and find that it induces the electric quadrupole moment of the quark-gluon plasma produced in heavy ion collisions: the "poles" of the produced fireball (pointing outside of the reaction plane) acquire additional positive electric charge, and the "equator" acquires additional negative charge. We point out that this electric quadrupole deformation lifts the degeneracy between the elliptic flows of positive and negative pions leading to $v_2(\\pi^+) < v_2(\\pi^-)$, and estimate the magnitude of the effect.
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.
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.
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.
Jiechen Xu; Jinfeng Liao; Miklos Gyulassy
2015-08-03T23:59:59.000Z
A new model (CUJET3.0) of jet quenching in nuclear collisions coupled to bulk data constrained (VISH2+1D) viscous hydrodynamic backgrounds is constructed by generalizing the perturbative QCD based (CUJET2.0) model to include possible non-perturbative chromodynamical features of the QCD confinement transition near $T_c\\approx 160$ MeV. Two competing mechanisms are considered: (1) the suppression of quark and gluon chromo-electric-charged (cec) degrees of freedom (aka the semi-QGP model of Pisarski et al) and (2) the emergence of chromo-magnetic-monopole (cmm) degrees of freedom (aka the magnetic scenario of Shuryak-Liao). This semi Quark Gluon Monopole Plasma (sQGMP) model depends on two free parameters: (1) the saturating value of the QCD running coupling $\\alpha_c$ below $T_c$ and (2) the ratio $c_m$ of color electric to magnetic screening scales. The value of $\\alpha_c$ is fixed by fitting to a $single$ LHC reference datum, $R^{ch}_{PbPb}(p_T=12{\\rm GeV/c})\\approx 0.3$ for 20-30% centrality. Consistency is then tested by comparing predictions to $all$ $R^h_{AA}(p_T>10{\\rm GeV/c})$, $v^h_2(p_T>10{\\rm GeV/c})$, $h=\\pi,D,B$ data simultaneously at both RHIC and LHC. Robustness to uncertainties in modeling the suppression of cec degrees of freedom is tested by comparing results based on lattice data for Polyakov loop versus for quark susceptibility. The emergent cmm degrees of freedom are shown to solve robustly the long standing $R_{AA}$ vs $v_2$ puzzle by predicting a maximum of the jet quenching parameter field $\\hat{q}(E,T)/T^3$ near $T_c$. Robustness and consistency of jet quenching with observed bulk perfect fluidity is demonstrated by extrapolating the sQGMP $\\hat{q}$ down to thermal energy $E\\sim 3 T$ scales and showing that the $\\eta/s \\approx T^3/\\hat{q}$ falls close to the unitarity bound, $1/4\\pi$, in the range $(1-2)T_c$.
Vovchenko, V; Satarov, L M; Mishustin, I N; Csernai, L P; Kisel, I; Stoecker, H
2015-01-01T23:59:59.000Z
We study the possibility that partonic matter produced at early stage of ultrarelativistic heavy-ion collisions is out of chemical equilibrium. It is assumed that initially this matter is mostly composed of gluons, but quarks and antiquarks are produced at later times. The dynamical evolution of partonic system is described by the Bjorken-like ideal hydrodynamics with a time dependent quark fugacity. The results of this model are compared with those obtained by assuming the complete chemical equilibrium of partons already at the initial stage. It is shown that in a chemically non-equilibrium scenario the entropy gradually increases, and about 25% of the total final entropy is generated during the hydrodynamic evolution of deconfined matter. We argue that the (anti)quark suppression included in this approach may be responsible for reduced (anti)baryon to meson ratios observed in heavy-ion collisions at LHC energies.
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.
Gaining (Mutual) Information about Quark/Gluon Discrimination
Andrew J. Larkoski; Jesse Thaler; Wouter J. Waalewijn
2014-12-03T23:59:59.000Z
Discriminating quark jets from gluon jets is an important but challenging problem in jet substructure. In this paper, we use the concept of mutual information to illuminate the physics of quark/gluon tagging. Ideal quark/gluon separation requires only one bit of truth information, so even if two discriminant variables are largely uncorrelated, they can still share the same "truth overlap". Mutual information can be used to diagnose such situations, and thus determine which discriminant variables are redundant and which can be combined to improve performance. Using both parton showers and analytic resummation, we study a two-parameter family of generalized angularities, which includes familiar infrared and collinear (IRC) safe observables like thrust and broadening, as well as IRC unsafe variants like $p_T^D$ and hadron multiplicity. At leading-logarithmic (LL) order, the bulk of these variables exhibit Casimir scaling, such that their truth overlap is a universal function of the color factor ratio $C_A/C_F$. Only at next-to-leading-logarithmic (NLL) order can one see a difference in quark/gluon performance. For the IRC safe angularities, we show that the quark/gluon performance can be improved by combining angularities with complementary angular exponents. Interestingly, LL order, NLL order, Pythia 8, and Herwig++ all exhibit similar correlations between observables, but there are significant differences in the predicted quark/gluon discrimination power. For the IRC unsafe angularities, we show that the mutual information can be calculated analytically with the help of a nonperturbative "weighted-energy function", providing evidence for the complementarity of safe and unsafe observables for quark/gluon discrimination.
A new method for determining the quark-gluon vertex
A. C. Aguilar; D. Binosi; D. Ibańez; J. Papavassiliou
2015-04-07T23:59:59.000Z
We present a novel nonperturbative approach for calculating the form factors of the quark-gluon vertex, in a general covariant gauge. The key ingredient of this method is the exact all-order relation connecting the conventional quark-gluon vertex with the corresponding vertex of the background field method, which is Abelian-like. When this latter relation is combined with the standard gauge technique, supplemented by a crucial set of transverse Ward identities, it allows the approximate determination of the nonperturbative behavior of all twelve form factors comprising the quark-gluon vertex, for arbitrary values of the momenta. The actual implementation of this procedure is carried out in the Landau gauge, in order to make contact with the results of lattice simulations performed in this particular gauge. The most demanding technical aspect involves the calculation of certain (fully-dressed) auxiliary three-point functions, using lattice data as input for the gluon propagators appearing in their diagrammatic expansion. The numerical evaluation of the relevant form factors in three special kinematical configurations (soft gluon and quark symmetric limit, zero quark momentum) is carried out in detail, finding rather good agreement with the available lattice data. Most notably, a concrete mechanism is proposed for explaining the puzzling divergence of one of these form factors observed in lattice simulations.
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.
Inclusive Two-Gluon and Valence Quark-Gluon Production in DIS and pA
Jamal Jalilian-Marian; Yuri V. Kovchegov
2005-03-17T23:59:59.000Z
We calculate production cross sections of a forward quark-gluon pair and of two gluons at mid-rapidity in Deep Inelastic Scattering and in high energy proton-nucleus collisions. The calculation is performed in the framework of the Color Glass Condensate formalism. We first calculate the cross sections in the quasi-classical approximation, which includes multiple rescatterings in the target. We then proceed to include the effects of non-linear small-x evolution in the production cross sections. It is interesting to note that our result for the two-gluon production cross section appears to be in direct violation of AGK cutting rules, which is the first example of such violation in QCD. The calculated quark-gluon and gluon-gluon production cross sections can be used to construct theoretical predictions for two-particle azimuthal correlations at RHIC and LHC (I^{p(d)A}) as well as for Deep Inelastic Scattering experiments at HERA and eRHIC.
Controversy concerning the definition of quark and gluon angular momentum
Leader, Elliot [Blackett laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)
2011-05-01T23:59:59.000Z
A major controversy has arisen in QCD as to how to split the total angular momentum into separate quark and gluon contributions, and as to whether the gluon angular momentum can itself be split, in a gauge-invariant way, into a spin and orbital part. Several authors have proposed various answers to these questions and offered a variety of different expressions for the relevant operators. I argue that none of these is acceptable and suggest that the canonical expression for the momentum and angular momentum operators is the correct and physically meaningful one. It is then an inescapable fact that the gluon angular momentum operator cannot, in general, be split in a gauge-invariant way into a spin and orbital part. However, the projection of the gluon spin onto its direction of motion, i.e. its helicity is gauge invariant and is measured in deep inelastic scattering on nucleons. The Ji sum rule, relating the quark angular momentum to generalized parton distributions, though not based on the canonical operators, is shown to be correct, if interpreted with due care. I also draw attention to several interesting aspects of QED and QCD, which, to the best of my knowledge, are not commented upon in the standard textbooks on field theory.
Anisotropic hydrodynamics for mixture of quark and gluon fluids
Florkowski, Wojciech; Ryblewski, Radoslaw; Tinti, Leonardo
2015-01-01T23:59:59.000Z
A system of equations for anisotropic hydrodynamics is derived that describes a mixture of anisotropic quark and gluon fluids. The consistent treatment of the zeroth, first and second moments of the kinetic equations allows us to construct a new framework with more general forms of the anisotropic phase-space distribution functions than those used before. In this way, the main difficiencies of the previous formulations of anisotropic hydrodynamics for mixtures have been overcome and the good agreement with the exact kinetic-theory results is obtained.
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.
Quark deconfinement and gluon condensate in a weak magnetic field
Alejandro Ayala; C. A. Dominguez; L. A. Hernandez; M. Loewe; Juan Cristobal Rojas; Cristian Villavicencio
2015-07-01T23:59:59.000Z
We study QCD finite energy sum rules (FESR) for the axial-vector current correlator in the presence of a magnetic field, in the weak field limit and at zero temperature. We find that the perturbative QCD as well as the hadronic contribution to the sum rules get explicit magnetic field-dependent corrections and that these in turn induce a magnetic field dependence on the deconfinement phenomenological parameter s_0 and on the gluon condensate. The leading corrections turn out to be quadratic in the field strength. We find from the dimension d=2 first FESR that the magnetic field dependence of s_0 is proportional to the absolute value of the light-quark condensate. Hence, it increases with increasing field strength. This implies that the parameters describing chiral symmetry restoration and deconfinement behave similarly as functions of the magnetic filed. Thus, at zero temperature the magnetic field is a catalysing agent of both chiral symmetry breaking and confinement. From the dimension d=4 second FESR we obtain the behavior of the gluon condensate in the presence of the external magnetic field. This condensate also increases with increasing field strength.
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.
A possible evidence of the hadron-quark-gluon mixed phase formation in nuclear collisions
V. A. Kizka; V. S. Trubnikov; K. A. Bugaev; D. R. Oliinychenko
2015-04-24T23:59:59.000Z
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 of data which are located at the center of mass collision energies 4.4-4.87 GeV and 10.8-12 GeV. At the collision energies below 4.4 GeV the hadron gas models describe data much better than the QGP one and, hence, we associate this region with hadron phase. At the collision energies between 5 GeV and 10.8 GeV and above 12 GeV we found that QGP models describe data essentially better than the hadron gas ones and, hence, these regions we associate with the quark-gluon phase. As a result, the collision energy regions 4.4-4.87 GeV and 10.8-12 GeV we interpret as the energies of the hadron-quark-gluon mixed phase formation. Based on these findings we argue that the most probable energy range of the QCD phase diagram (tri)critical endpoint is 12-14 GeV.
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.
\\THE POOL OF QUARKS AND GLUONS" The protons and neutrons, which make up nuclei, are not elementary in a simpli#12;ed way as a pool with three balls (quarks) of di#11;erent colours. Quarks cannot escape from the proton in the same way as balls are kept inside the pool by the boundaries. The quarks move freely except
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.
Static potential for the quark-antiquark-gluon hybrid system in lattice QCD
Marco Cardoso; Pedro Bicudo; Orlando Oliveira
2007-10-09T23:59:59.000Z
The static gluon-quark-antiquark interaction is investigated using lattice QCD techniques. A Wilson loop adequate to the static hybrid three-body system is developed and, using a $24^3 \\times 48$ periodic lattice with $\\beta = 6.2$, the potential energy of the system is measured for different geometries. For the medium range behaviour, when the quarks are far apart, we find a string tension which is compatible with two fundamental strings. On the other hand, when the quark and antiquark are nearby, the string tension is larger than two fundamental strings and is compatible with the Casimir scaling.
Probing Quark-Gluon Structure of Matter with e-p and e-A Reactions
Jian-Ping Chen
2011-11-01T23:59:59.000Z
Understanding the strong interaction (QCD) in the truly strong ('non-perturbative') region remains a major challenge in modern physics. Nucleon and nuclei provide natural laboratories to study the strong interaction. The quark-gluon structure of the nucleon and nuclei are important by themselves since they are the main (>99%) part of the visible world. With electroweak interaction well-understood, e-p and e-A are clean means to probe the nucleon and nuclear structure and to study the strong interaction (QCD). Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinally-polarized parton (quark and gluon) distributions (PDFs). It has becoming clear that transverse spin and transverse structure (both transverse spatial structure via generalized parton distributions (GPDs) and transverse momentum structure via transverse- momentum-dependent distributions (TMDs)) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction(QCD). The transverse spin, GPDs and TMDs have been the subjects of increasingly intense theoretical and experimental study recently. With 12 GeV energy upgrade, Jefferson Lab (JLab) will provide the most precise multi-dimensional map of the TMDs and GPDs in the valence quark region through Semi-Inclusive DIS (SIDIS) and Deep-Exclusive experiments, providing a 3-d partonic picture of the nucleon in momentum and spatial spaces. The precision information on TMDs and GPDs will provide access to the quark orbital angular momentum and its correlation with the quark and the nucleon spins. The planned future Electron-Ion Collider (EIC) will enable a precision study of the TMDs and GPDs of the sea quarks and gluons, in addition to completing the study in the valence region. The EIC will also open a new window to study the role of gluons in nuclei.
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
2015-06-20T23:59:59.000Z
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 compared to the data, is in agreement with the Au$+$Au measurement at $p_{T}photons will follow the modified $n_{q}$-scaling laws seen in identified hadron $v_{n}$ with an $n_{q}$ value of two.
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.
Interpretation of Vector-like Quark Searches: Heavy Gluons in Composite Higgs Models
Juan Pedro Araque; Nuno Filipe Castro; Jose Santiago
2015-07-20T23:59:59.000Z
Pair production of new vector-like quarks in pp collisions is considered model independent as it is usually dominated by QCD production. We discuss the interpretation of vector-like quark searches in the case that QCD is not the only relevant production mechanism for the new quarks. In particular we consider the effect of a new massive color octet vector boson with sizeable decay branching ratio into the new quarks. We pay special attention to the sensitivity of the Large Hadron Collider experiments, both in run-1 and early run-2, to differences in the kinematical distributions from the different production mechanisms. We have found that even though there can be significant differences in some kinematical distributions at the parton level, the differences are washed out at the reconstruction level. Thus, the published experimental results can be reinterpreted in models with heavy gluons by simply rescaling the production cross section.
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.
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.
How do quarks and gluons lose energy in the QGP?
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Tannenbaum, M. J.
2015-03-10T23:59:59.000Z
RHIC introduced the method of hard scattering of partons as an in-situ probe of the the medium produced in A+A collisions. A suppression, RAA ? 0.2 relative to binary-scaling, was discovered for ?? production in the range 5 T NN = 200 GeV, and surprisingly also for single-electrons from the decay of heavy quarks. Both these results have been confirmed in Pb+Pb collisions at the LHC at ?sNN = 2.76 TeV. Interestingly, in this ?T range the LHC results for pions nearly overlap the RHIC results. Thus, due to the flattermore »spectrum, the energy loss in the medium at LHC in this ?T range must be ~ 40% larger than at RHIC. Unique at the LHC are the beautiful measurements of the fractional transverse momentum imbalance 1 (?-carotT2/?-carotT1) of di-jets in Pb+Pb collisions. At the Utrecht meeting in 2011, I corrected for the fractional imbalance of di-jets with the same cuts in p-p collisions and showed that the relative fractional jet imbalance in Pb+Pb/p-p is ? 15% for jets with 120 T1 T jet ? 10 20 GeV/c, which appear to show a much larger fractional jet imbalance ? 45% in this lower ?-carotT range. The variation of apparent energy loss in the medium as a function of both ?T and ?sNN is striking and presents a challenge to both theory and experiment for improved understanding. There are many other such unresolved issues, for instance, the absence of evidence for a q-carot effect, due to momentum transferred to the medium by outgoing partons, which would widen the away-side di-jet and di-hadron correlations in a similar fashion as the kT-effect. Another issue well known from experiments at the CERN ISR, SpS and SpS collider is that parton-parton hard-collisions make negligible contribution to multiplicity or transverse energy production in p-p collisionssoft particles, with ?T AAch/d? = [(1 - x) (Npart)dNppch/d?2 + x (NcolldNppch/d?], seems to be an unphysical way to understand the deviation from Npart scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements.« less
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.
Study of gluon versus quark fragmentation in ??gg? and e(+)e(-)?qq? events at s?=10 GeV
Baringer, Philip S.
1997-07-01T23:59:59.000Z
extract the mean multiplicities as a function of gg or q qÆ mass, for pure ggg and q qÆg samples. As shown in Fig. 4, the ratio of ^ Nchrg& resulting from gluon fragmentation to ^Nchrg& from quark fragmentation is Rchrg51.0460.02, after all the afore...& for gluons to ^Nchrg& for quarks mea- sured here is smaller than those found by the OPAL, ALEPH, SLD, and DELPHI experiments, at As;MZ0. The ratios compare as follows. Collaboration ^ N &g /^N&q Kinematic regime CLEO 96 1.0460.05 ^ E jet&,7 GeV DELPHI @4# 1...
Sungwoong Cho; Suyong Choi; Sehwook Lee; JaeHoon Lim; SungWoo Youn
2014-11-30T23:59:59.000Z
We report a measurement of the fraction of top quark pair events produced via gluon-gluon fusion in $p\\bar{p}$ collisions at $\\sqrt{s} = 1.96 ~\\rm TeV$ in lepton+jets final states using the full RunII data set corresponding to $9.7 ~\\rm fb^{-1}$ of integrated luminosity collected by the D\\O\\ experiment. We utilize a boosted decision tree to distinguish top quark pair events produced by $q\\bar{q}$ annihilation and $gg$ fusion. We perform a template fit to extract the $t\\bar{t}$ production fraction via $gg$ fusion and find $f_{gg} = 0.096 \\pm 0.039 ~(\\rm stat.) ~^{+0.077}_{-0.062} ~(\\rm syst.)$.
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.
Light-quark and gluon jet discrimination in pp collisions at ?s = 7 TeV with the ATLAS detector
Taylor, Frank E.
A likelihood-based discriminant for the identification of quark- and gluon-initiated jets is built and validated using 4.7 fb ?1 of protonproton collision data at s?=7 TeV collected with the ATLAS detector at the LHC. ...
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 worlds first polarized electron-proton collider, and the worlds 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.
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.
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.
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.
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
to the Fourier trans- form of the spatial potential ansatz, ~G m2G=(q 2 + ~m2D) 2. In a similar manner as the Coulomb part, the string interaction behaves as a potential as well, ~V s = V s 2mg j u(p3)u(p1)2mgg (p4) (p2) j: (3.36) Calculating... of the intermediate states. To complete the analysis of the ~T-matrix, the two-particle propagator GgQ must be speci ed. It depends on the scheme of the underlying BS equation, where for this thesis I focus on the Thompson scheme, GgQ(q) = m(q) E !g(q) !Q(q) g...
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.
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.
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...
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...
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.
M. Cardoso; N. Cardoso; P. Bicudo
2009-12-16T23:59:59.000Z
The chromoelectric and chromomagnetic 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 with two spatial geometries, one with a U shape and another with an L shape. The particular cases of the two gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This microscopic study of the colour fields is relevant to understand the structure of hadrons, in particular of the hybrid excitation of mesons. This also contributes to understand confinement with flux tubes and to discriminate between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.
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.
Study on Screenning Length of Quark-AntiQuark Pair in a Hot Plasma of Two Dimensional Sphere
Atmaja, Ardian Nata
2011-01-01T23:59:59.000Z
We study screening length of a quark-antiquark pair moving in a plasma, corresponds to four dimensional AdS-Schwarzschild Black Hole, in AdS/CFT correspondence. The geodesic solution of the ends of string at the boundary reduces the problem to the motion in equatorial plane in which the separation length $L$ of quark-antiquark pair is parallel to the angular velocity $\\omega$. The string configuration for quark-antiquark pair is parameterized by momentum transfer $P$ which is related to momentum transfer in the drag force configuration. We compare the result by computing the screening length in quark-antiquark reference frame where the gravity dual is four dimensional Kerr-AdS Black Hole and we find a relation between mass parameters $M_{Sch}$ of Schwarzschild-AdS Black Hole and $M_{Kerr}$ of Kerr-AdS Black Hole in large mass limit.
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.
Large mass dileptons from the passage of jets through a quark gluon plasma
Srivastava, DK; Gale, C.; Fries, Rainer J.
2003-01-01T23:59:59.000Z
-09-05 Proceedings of the 14th International Conference for Enhanced Building Operations, Beijing, China, September 14-17, 2014 Agenda ? Room Control fundamentals and evolution ? Challenges ? The Smart Room Control approach ? Benefits ? Market applications ? Typical... Configurations ? Summary ESL-IC-14-09-05 Proceedings of the 14th International Conference for Enhanced Building Operations, Beijing, China, September 14-17, 2014 Room Control System Fundamentals ? HVAC ? Terminal units ? Temperature and air flow control...
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.
High momentum dilepton production from jets in a quark gluon plasma
Turbide, Simon; Gale, Charles; Srivastava, Dinesh K.; Fries, Rainer J.
2006-01-01T23:59:59.000Z
with a Monte Carlo code, EGS4, to calculate absorbed fraction of energy and specific absorbed fraction of energy for photon and electron sources located in one of thirteen chosen source regions. These calculations were made for radiations in the energy...
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.
Hard Probes of the Quark Gluon Plasma in Heavy Ion Collisions
Salgado, Carlos A
2011-01-01T23:59:59.000Z
The medium-modifications of processes characterized by the presence of a hard scale provide the most diverse tools to characterize the properties of the matter created in high-energy nuclear collisions. Indeed, jet quenching, the suppression of particles produced at high transverse momentum, has been established at RHIC almost a decade ago as one of the main tools in heavy-ion collisions. The melting of quarkonia is expected to provide also information about the temperature and the properties of the produced medium. The beginning of the LHC era for hot QCD studies starts with the first nuclear beams in 2010. The amount of information produced by this first run is overwhelming: The three experiments with nuclear program (ALICE, ATLAS and CMS) have provide new results in basically all subjects considered in previous experiments and have also shown the potential to make nuclear collisions at the TeV scale for the first time. I will review what the results from both RHIC and LHC imply for our understanding of hot...
Geek-Up[11.05.10]: Quark Gluon Plasma, Solar-Power Generating Windows and
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J/psi Production in Quark-Gluon Plasma (Journal Article) | SciTech Connect
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ABSORPTION OF HARD AND THERMAL PHOTONS IN A QUARK-GLUON PLASMA AND
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Geek-Up[11.05.10]: Quark Gluon Plasma, Solar-Power Generating...
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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"...
Subjet multiplicity of gluon and quark jets reconstructed with the k? algorithm in pp-bar collisions
Baringer, Philip S.; Bean, Alice; Coppage, Don; Hebert, C.; Abazov, V. M.; Abbott, B.; Abdesselam, A.; Abolins, M.; Abramov, V.
2002-02-07T23:59:59.000Z
and uranium noise, while a zero-bias event at low luminosity has only the offset from uranium noise. To measure Oue , we again compare two samples of jets. Minimum-bias events as measured by the DO? calorim- eter at low luminosity are added to Monte Carlo jet... jets is more complicated than in e1e2 annihilations. We approach this issue by comparing central jet samples at As51800 GeV and 630 GeV, with the samples described in Sec. IV. For moderate jet pT ~55100 GeV!, the As 51800 GeV sample is gluon-enriched...
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.
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.
Huey-Wen Lin; Keh-Fei Liu
2011-11-02T23:59:59.000Z
It is argued by the author that the canonical form of the quark energy-momentum tensor with a partial derivative instead of the covariant derivative is the correct definition for the quark momentum and angular momentum fraction of the nucleon in covariant quantization. Although it is not manifestly gauge invariant, its matrix elements in the nucleon will be non-vanishing and are gauge invariant. We test this idea in the path-integral quantization by calculating correlation functions on the lattice with a gauge-invariant nucleon interpolation field and replacing the gauge link in the quark lattice momentum operator with unity, which corresponds to the partial derivative in the continuum. We find that the ratios of three-point to two-point functions are zero within errors for both the u and d quarks, contrary to the case without setting the gauge links to unity.
Parton Energy Loss in Two-Stream Plasma System
M. E. Carrington; K. Deja; St. Mrowczynski
2012-01-06T23:59:59.000Z
The energy loss of a fast parton scattering elastically in a weakly coupled quark-gluon plasma is formulated as an initial value problem. The approach is designed to study an unstable plasma, but it also reproduces the well known result of energy loss in an equilibrium plasma. A two-stream system, which is unstable due to longitudinal chromoelectric modes, is discussed here some detail. In particular, a strong time and directional dependence of the energy loss is demonstrated.
Higgs Boson Production via Gluon Fusion: Soft-Gluon Resummation including Mass Effects
Schmidt, Timo
2015-01-01T23:59:59.000Z
We analyze soft and collinear gluon resummation effects at the N$^3$LL level for Standard Model Higgs boson production via gluon fusion $gg\\to H$ and the neutral scalar and pseudoscalar Higgs bosons of the minimal supersymmetric extension at the N$^3$LL and NNLL level, respectively. We introduce refinements in the treatment of quark mass effects and subleading collinear gluon effects within the resummation. Soft and collinear gluon resummation effects amount to up to about 5% beyond the fixed-order results for scalar and pseudoscalar Higgs boson production.
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 ...
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...
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.
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.
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
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.
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.
Toward an understanding of the $R_{AA}$ and $v_2$ puzzle for heavy quarks
Scardina, Francesco; Plumari, Salvatore; Bellone, Jessica I; Greco, Vincenzo
2015-01-01T23:59:59.000Z
One of the primary aims of the ongoing nuclear collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies is to create a Quark Gluon Plasma (QGP). The heavy quarks constitutes a unique probe of the QGP properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$ related to heavy quark has been observed which challenged all the existing models.\\\\ We discuss how the temperature dependence of the heavy quark drag coefficient can address for a large part of such a puzzle. We have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA}(p_T)$ experimentally observed at RHIC energy. We have found that for the same $R_{AA}(p_T)$ one can generate $2-3$ times more $v_{2}$ depending on the temperature dependence of the heavy quark drag...
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.
Dynamical gluon mass and linear confinement
Ayala, Cesar; Vento, Vicente
2015-01-01T23:59:59.000Z
We define a non-perturbative running coupling in terms of a gluon mass function, similar to that used in some Dyson-Schwinger approaches. From this coupling, which satisfies asymptotic freedom and describes correctly the singularity structure of confinement, a static quark-antiquark potential is constructed. We calculate the bottomonium and charmonium spectra below the first open flavor meson-meson thresholds and show that for a small range of values of the free parameter determining the gluon mass function a good agreement with data is attained.
Strongly coupled plasma with electric and magnetic charges
Jinfeng Liao; Edward Shuryak
2006-12-12T23:59:59.000Z
A number of theoretical and lattice results lead us to believe that Quark-Gluon Plasma not too far from $T_c$ contains not only electrically charged quasiparticles -- quarks and gluons -- but magnetically charged ones -- monopoles and dyons -- as well. Although binary systems like charge-monopole and charge-dyon were considered in details before in both classical and quantum settings, it is the first study of coexisting electric and magnetic particles in many-body context. We perform Molecular Dynamics study of strongly coupled plasmas with $\\sim 1000$ particles and different fraction of magnetic charges. Correlation functions and Kubo formulae lead to such transport properties as diffusion constant, shear viscosity and electric conductivity: we compare the first two with empirical data from RHIC experiments as well as results from AdS/CFT correspondence. We also study a number of collective excitations in these systems.
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.
An in-Medium Heavy-Quark Potential from the $Q\\bar{Q}$ Free Energy
Shuai Y. F. Liu; Ralf Rapp
2015-01-30T23:59:59.000Z
We investigate the problem of extracting a static potential between a quark and its antiquark in a quark-gluon plasma (QGP) from lattice-QCD computations of the singlet free energy, $F_{Q\\bar{Q}}(r)$. We utilize the thermodynamic $T$-matrix formalism to calculate the free energy from an underlying potential ansatz resummed in ladder approximation. Imaginary parts of both $Q\\bar Q$ potential-type and single-quark selfenergies are included as estimated from earlier results of the $T$-matrix approach. We find that the imaginary parts, and in particular their (low-) energy dependence, induce marked deviations of the (real part of the) potential from the calculated free energy. When fitting lattice results of the latter, the extracted potential is characterized by significant long-range contributions from remnants of the confining force. We briefly discuss consequences of this feature for the heavy-quark transport coefficient in the QGP.
Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons
Boer, Daniel; /Groningen, KVI; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; Mulders, Piet J.; /Brussels U., IIHE; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-02-07T23:59:59.000Z
We show that the unmeasured distribution of linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production both in electron-hadron and hadron-hadron collisions. We present expressions for the simplest cos 2{phi} asymmetries and estimate their maximal value in the particular case of electron-hadron collisions. Measurements of the linearly polarized gluon distribution in the proton should be feasible in future EIC or LHeC experiments.
Magnetic Fields Boosted by Gluon Vortices in Color Superconductivity
Efrain J. Ferrer; Vivian de la Incera
2006-08-28T23:59:59.000Z
We investigate the effects of an external magnetic field in the gluon dynamics of a color superconductor with three massless quark flavors. In the framework of gluon mean-field theory at asymptotic densities, we show that the long-range component $\\widetilde{H}$ of the external magnetic field that penetrates the CFL phase produces an instability when its strength becomes larger than the Meissner mass of the charged gluons. As a consequence, the magnetic field causes the formation of a vortex state characterized by the condensation of charged gluons and the creation of magnetic flux tubes. Inside the flux tubes the magnetic field is stronger than the applied one. This antiscreening effect is connected to the anomalous magnetic moment of the gluon field. We suggest how this same mechanism could serve to remove the chromomagnetic instabilities existing in gapless color superconductivity.
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
Luķs 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.
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.
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.
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).
Probing the Linear Polarization of Gluons in Unpolarized Hadrons at EIC
Boer, Daniel; /Groningen, KVI; Brodsky, Stanley J.; /SLAC; Mulders, Piet J.; /Vrije U., Amsterdam; Pisano, Cristian; /Cagliari U. /INFN, Cagliari
2011-08-17T23:59:59.000Z
Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this TMD distribution of linearly polarized gluons is through cos 2{phi} asymmetries in heavy quark pair or dijet production in electron-hadron collisions. Future EIC or LHeC experiments are ideally suited for this purpose. Here we estimate the maximum asymmetries for EIC kinematics.
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.
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.
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.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2014-01-01T23:59:59.000Z
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of generalized transverse momentum distributions, cannot be observed in scattering processes involving a single hadronic reaction plane.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Aurore Courtoy; Gary R. Goldstein; J. Osvaldo Gonzalez Hernandez; Simonetta Liuti; Abha Rajan
2014-12-01T23:59:59.000Z
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of generalized transverse momentum distributions, cannot be observed in scattering processes involving a single hadronic reaction plane.
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.
Search for pair production of excited top quarks in the lepton + jets final state
Apyan, Aram
A search is performed for pair-produced spin-3/2 excited top quarks (t[superscript ?][Æ over t][superscript ?]), each decaying to a top quark and a gluon. The search uses data collected with the CMS detector from pp ...
Initial temperature and EoS of quark matter from direct photons
Mate Csanad; Imre Majer
2011-09-04T23:59:59.000Z
The time evolution of the quark gluon plasma created in gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) can be described by hydrodynamical models. Distribution of hadrons reflects the freeze-out state of the matter. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon spectra. Distributions of low energy photons was published in 2010 by PHENIX. In this paper we analyze a 3+1 dimensional solution of relativistic hydrodynamics and calculate momentum distribution of direct photons. Using earlier fits of this model to hadronic spectra, we compare photon calculations to measurements and find that the initial temperature of the center of the fireball is at least 519+-12 MeV, while for the equation of state we get c_s= 0.36+-0.02.
Trace Anomaly and Dimension Two Gluon Condensate Above the Phase Transition
Megias,E.; Ruiz Arriola, E.; Salcedo, L.L.
2008-02-04T23:59:59.000Z
The dimension two gluon condensate has been used previously within a simple phenomenological model to describe power corrections from available lattice data for the renormalized Polyakov loop and the heavy quark-antiquark free energy in the deconfined phase of QCD. The QCD trace anomaly of gluodynamics also shows unequivocal inverse temperature power corrections which may be encoded as dimension two gluon condensate. We analyze lattice data of the trace anomaly and compare with other determinations of the condensate from previous references, yielding roughly similar numerical values.
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.
An analysis of 4-quark energies in SU(2) lattice Monte Carlo
Sadataka Furui; Bilal Masud
1998-09-12T23:59:59.000Z
Energies of four-quark systems with the tetrahedral geometry measured by the static quenched SU(2) lattice Monte Carlo method are analyzed by parametrizing the gluon overlap factor in the form exp(-[bs EA+{\\sqrt bs}FP]) where A and P are the area and the perimeter defined mainly by the positions of the four quarks, bs is the string constant in the 2-quark potentials and E, F are constants.
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
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.
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.
Quark tensor charge and electric dipole moment within the Schwinger-Dyson formalism
Nodoka Yamanaka; Takahiro M. Doi; Shotaro Imai; Hideo Suganuma
2014-12-18T23:59:59.000Z
We calculate the tensor charge of the quark in the QCD-like theory in the Landau gauge using the Schwinger-Dyson formalism. It is found that the dressed tensor charge of the quark is significantly suppressed against the bare quark contribution, and the result agrees qualitatively with the analyses in the collinear factorization approach and lattice QCD. We also analyze the quark confinement effect with the phenomenological strong coupling given by Richardson, and find that this contribution is small. We show that the suppression of the quark tensor charge is due to the superposition of the spin flip of the quark arising from the successive emission of gluons which dress the tensor vertex. We also consider the relation between the quark and the nucleon electric dipole moments by combining with the simple constituent quark model.
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.
Chemical Potential Dependence of Chiral Quark Condensate in Dyson-Schwinger Equation Approach of QCD
Lei Chang; Huan Chen; Bin Wang; Wei Yuan; Yu-xin Liu
2006-11-06T23:59:59.000Z
We propose a chemical potential dependent effective gluon propagator and study the chiral quark condensate in strongly interacting matter in the framework of Dyson-Schwinger equation approach. The obtained results manifest that, as the effect of the chemical potential on the effective gluon propagator is taken into account, the chiral quark condensate decreases gradually with the increasing of the chemical potential if it is less than the critical value, and the condensate vanishes suddenly at the critical chemical potential. The inclusion of the chemical potential in the effective gluon propagator enhances the decreasing rate and decreases the critical chemical potential. It indicates that the chiral symmetry can be restored completely at a critical chemical potential and restored partially as the chemical potential is less than the critical value. If the effective gluon propagator is independent of the chemical potential, the chiral symmetry can only be restored suddenly but no gradual restoration.
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.
Sea Quark Flavor Asymmetry of Hadrons in Statistical Balance Model
Bin Zhang; Yong-Jun Zhang
2010-10-20T23:59:59.000Z
We derive a Menta Carlo method to simulate kinetic equilibrium ensemble, and get the same sea-quark flavor asymmetry as the linear equations method in statistical model. In the recent paper, we introduce the spilt factors to indicate the quarks' or gluons' spilt $g\\rightarrow q\\bar{q}(gg)$ and $q\\rightarrow qg$ ability. We obtain the almost fixed asymmetry value $0.12-0.16$ which consists with experimental measurements for proton, when the spilt factors vary in a very wide range over four orders of magnitude. So, we proof the sea quark asymmetry can be derived from statistic principle and not sensitively dependents on the dynamics details of quarks and gluons in proton. We also apply the Menta Carlo method of statistical model to predict the sea-quark asymmetry values for $K$ mesons, octet baryons $\\Sigma$,$\\Xi$ and $\\Delta$ baryons, even for exotic pentaquark states. All these asymmetry values just only dependent on the valence quarks numbers in those hadrons.
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. ...
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.
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.
Electric Flux Tube in Magnetic Plasma
Jinfeng Liao; Edward Shuryak
2007-12-06T23:59:59.000Z
In this paper we study a methodical problem related to the magnetic scenario recently suggested and initiated by the authors \\cite{Liao_ES_mono} to understand the strongly coupled quark-gluon plasma (sQGP): the electric flux tube in monopole plasma. A macroscopic approach, interpolating between Bose condensed (dual superconductor) and classical gas medium is developed first. Then we work out a microscopic approach based on detailed quantum mechanical calculation of the monopole scattering on electric flux tube, evaluating induced currents for all partial waves. As expected, the flux tube looses its stability when particles can penetrate it: we make this condition precise by calculating the critical value for the product of the flux tube size times the particle momentum, above which the flux tube dissolves. Lattice static potentials indicate that flux tubes seem to dissolve at $T>T_{dissolution} \\approx 1.3 T_c$. Using our criterion one gets an estimate of the magnetic density $n\\approx 4.4 \\sim 6.6 fm^{-3}$ at this temperature.
Effects of quark chemical equilibration on thermal photon elliptic flow
Akihiko Monnai
2014-12-25T23:59:59.000Z
Large hadronic elliptic flow $v_2$ is considered as an evidence for the existence of a strongly-coupled QGP fluid in high-energy heavy-ion collisions. On the other hand, direct photon $v_2$ has recently been found to be much larger than hydrodynamic estimations, which is recognized as "photon $v_2$ puzzle". In this study, I discuss the implication of late production of quarks in an initially gluon-rich medium because photons are coupled to quarks. Numerical analyses imply that thermal photon $v_2$ can be visibly enhanced. This indicates that interplay of equilibration processes and collective expansion would be important.
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.
Electric and magnetic screenings of gluons in a model with dimension-2 gluon condensate
Fukun Xu; Mei Huang
2011-11-22T23:59:59.000Z
Electric and magnetic screenings of the thermal gluons are studied by using the background expansion method in a gluodynamic model with dimension-2 gluon condensate. At low temperature, the electric and magnetic gluons are degenerate. With the increasing of temperature, it is found that the electric and magnetic gluons start to split at certain temperature $T_0$. The electric screening mass changes rapidly with temperature when $T>T_0$, and the Polyakov loop expectation value rises sharply around $T_0$ from zero in the vacuum to a value around 0.8 at high temperature. This suggests that the color electric deconfinement phase transition is driven by electric gluons. It is also observed that the magnetic screening mass keeps almost the same as its vacuum value, which manifests that the magnetic gluons remains confined. Both the screening masses and the Polyakov loop results are qualitatively in agreement with the Lattice calculations.
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.
Basic features of the pion valence-quark distribution function
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Chang, Lei; Mezrag, Cédric; Moutarde, Hervé; Roberts, Craig D.; Rodrķguez-Quintero, Jose; Tandy, Peter C.
2014-10-07T23:59:59.000Z
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 rainbowladder 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 amore »realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, q?(x); namely, at a characteristic hadronic scale, q?(x)~(1-x)2 for x?0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.« less
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.
Strange quark matter in strong magnetic fields within a confining model
Monika Sinha; Xu-Guang Huang; Armen Sedrakian
2013-08-01T23:59:59.000Z
We construct an equation of state of strange quark matter in strong magnetic field within a confining model. The confinement is modeled by means of the Richardson potential for quark-quark interaction modified suitably to account for strong magnetic field. We compare our results for the equation of state and magnetization of matter to those derived within the MIT bag model. The differences between these models arise mainly due to the momentum dependence of the strong interaction between quarks in the Richardson model. Specifically, we find that the magnetization of strange quark matter in this model has much more pronounced de Haas-van Alf\\'{v}en oscillations than in the MIT bag model, which is the consequence of the (static) gluon-exchange structure of the confining potential.
The Specific Heat of Normal, Degenerate Quark Matter: Non-Fermi Liquid Corrections
Daniel Boyanovsky; H. J. de Vega
2001-02-26T23:59:59.000Z
In normal degenerate quark matter, the exchange of dynamically screened transverse gluons introduces infrared divergences in the quark self-energies that lead to the breakdown of the Fermi liquid description. If the core of neutron stars are composed of quark matter with a normal component, cooling by direct quark Urca processes may be modified by non-Fermi liquid corrections. We find that while the quasiparticle density of states is finite and non-zero at the Fermi surface, its frequency derivative diverges and results in non-Fermi liquid corrections to the specific heat of the normal, degenerate component of quark matter. We study these non-perturbative non-Fermi liquid corrections to the specific heat and the temperature dependence of the chemical potential and show that these lead to a reduction of the specific heat.
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.
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.
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.
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.
Tomomi Ishikawa; Yasumichi Aoki; Jonathan M. Flynn; Taku Izubuchi; Oleg Loktik
2011-05-16T23:59:59.000Z
We discuss perturbative O(g^2a) matching with static heavy quarks and domain-wall light quarks for lattice operators relevant to B-meson decays and $B^0$-$\\bar{B}^0$ mixing. The chiral symmetry of the light domain-wall quarks does not prohibit operator mixing at O(a) for these operators. The O(a) corrections to physical quantities are non-negligible and must be included to obtain high-precision simulation results for CKM physics. We provide results using plaquette, Symanzik, Iwasaki and DBW2 gluon actions and applying APE, HYP1 and HYP2 link-smearing for the static quark action.
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.; Įlvarez Gonzįlez, 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.; dAscenzo, N.; Datta, M.; de Barbaro, P.; DellOrso, M.; Demortier, L.; Deninno, M.; Devoto, F.; dErrico, M.; Di Canto, A.; Di Ruzza, B.; Dittmann, J. R.; DOnofrio, 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.; Gonzįlez, 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.; Martķnez, 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 ttÆg. 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.
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.; Įlvarez Gonzįlez, 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 ttÆg. 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
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
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.; Rodrķguez-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 QCDs DysonSchwinger equations and exemplified via the pions 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 pions valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to definemore »the pions 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, |b?|), which provide a qualitatively sound picture of the pions dressed-quark structure at a hadronic scale. We evolve the distributions to a scale ? = 2 GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.« less
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.
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.
Multi-Quark Energies in SU(2) Lattice Gauge Theory
A. M. Green; C. Michael; J. E. Paton; M. E. Sainio
1993-01-15T23:59:59.000Z
Energies of four-quark systems have been extracted in a quenched SU(2) lattice Monte Carlo calculation for two different geometries, rectangular and colinear, with $\\beta=2.4$ and lattice size $16^3\\times 32$. Also, by going to a lattice $24^3\\times 32$ and to $\\beta=2.5$, the effect of the finite lattice size and scaling are checked. An attempt is made to understand these results in terms of a model based on interquark two-body potentials but modified very significantly by a phenomenological gluon-field overlap factor.
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.
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.
Higgs boson pair production: top quark mass effects at NLO and NNLO
Grigo, Jonathan; Steinhauser, Matthias
2015-01-01T23:59:59.000Z
We compute next-to-next-to-leading order QCD corrections to the gluon-induced production cross section of Higgs boson pairs in the large top quark mass limit using the soft-virtual approximation. In the limit of infinitely-heavy top quark we confirm the results in the literature. We add two more expansion terms in the inverse top quark mass to the $M_t\\to\\infty$ result. Since the $1/M_t$ expansion converges poorly, we try to improve on it by factorizing the exact leading order cross section. We discuss two ways of doing that and conclude that the finite top quark mass effects shift the cross section at most by about 10\\% at next-to-leading order and by about 5\\% at next-to-next-to-leading order.
Continuum extrapolation of energies of a four-quark system in lattice gauge theory
Petrus Pennanen
1997-01-12T23:59:59.000Z
A continuum extrapolation of static two- and four-quark energies calculated in quenched SU(2) lattice Monte Carlo is carried out based on Sommer's method of setting the scale. The beta-function is obtained as a side product of the extrapolations. Four-quark binding energies are found to be essentially constant at beta >= 2.35 unlike the two-body potentials. A model for four-quark energies, with explicit gluonic degrees of freedom removed, is fitted to these energies and the behaviour of the parameters of the model is investigated. An extension of the model using the first excited states of the two-body gluon field as additional basis states is found to be necessary for quarks at the corners of regular tetrahedra.
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
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...
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.
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
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.
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.
Gluons in our future | Jefferson Lab
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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:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5 TablesExports(Journal Article)41clothThe Bonneville Power AdministrationHawaiiEnergyFloridaOutlook Mary Novak Managing Director IHS1InitiativesGluons in
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.
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.
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.
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...
Phenomenological analysis of Higgs boson production through gluon fusion in association with jets
Nicolas Greiner; Stefan Hoeche; Gionata Luisoni; Marek Schonherr; Jan-Christopher Winter; Valery Yundin
2015-06-02T23:59:59.000Z
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 taking the difference between the inclusive H+2 jets and the inclusive H+3 jets result.
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.
Qi Liu; Norman H. Christ; Chulwoo Jung
2012-06-01T23:59:59.000Z
We present a systematic study of the effectiveness of light quark mass reweighting. This method allows a single lattice QCD ensemble, generated with a specific value of the dynamical light quark mass, to be used to determine results for other, nearby light dynamical quark masses. We study two gauge field ensembles generated with 2+1 flavors of dynamical domain wall fermions with light quark masses m_l=0.02 (m_\\pi=620 MeV) and m_l=0.01 (m_\\pi=420 MeV). We reweight each ensemble to determine results which could be computed directly from the other and check the consistency of the reweighted results with the direct results. The large difference between the 0.02 and 0.01 light quark masses suggests that this is an aggressive application of reweighting as can be seen from fluctuations in the magnitude of the reweighting factor by four orders of magnitude. Never-the-less, a comparison of the reweighed topological charge, average plaquette, residual mass, pion mass, pion decay constant, and scalar correlator between these two ensembles shows agreement well described by the statistical errors. The issues of the effective number of configurations and finite sample size bias are discussed. An examination of the topological charge distribution implies that it is more favorable to reweight from heavier mass to lighter quark mass.
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.
ALICE ATLAS Cover 3 decades of energy
= nuclear particles = mesons, baryons Courtesy Nat. Geographic, Vol. 185, No. 1, 1994 Ā Graphics by Chuck Harris (Yale) 6th Odense Winter School on Theoretical Physics, 20 Quark-Gluon Plasma Ā· Standard Model?" #12;How to Make Quark Soup!! Nuclear particles (quarks are confined) Melt the particlesQuark Gluon
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.
Geek-Up[12.03.2010]: Halomonadaceae Bacteria and the Return of Quark Gluon
Broader source: Energy.gov (indexed) [DOE]
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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...
The study of quark-gluon matter in high-energy nucleus-nucleus collisions
A. Andronic
2012-10-30T23:59:59.000Z
A short overview is given on the study of hot matter produced in relativistic nucleus-nucleus collisions, with emphasis on recent measurements at the LHC.
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%.
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 $N_\\tau \\le 22$.
Lorentz and CPT Violation in Top-Quark Production and Decay
Berger, Micheal S; Liu, Zhi
2015-01-01T23:59:59.000Z
The prospects are explored for testing Lorentz and CPT symmetry in the top-quark sector. We present the relevant Lagrange density, discuss physical observables, and describe the signals to be sought in experiments. For top-antitop pair production via quark or gluon fusion with subsequent semileptonic or hadronic decays, we obtain the matrix element in the presence of Lorentz violation using the narrow-width approximation. The issue of testing CPT symmetry in the top-quark sector is also addressed. We demonstrate that single-top production and decay is well suited to a search for CPT violation, and we present the matrix elements for single-top production in each of the four tree-level channels. Our results are applicable to searches for Lorentz violation and studies of CPT symmetry in collider experiments, including notably high-statistics top-antitop and single-top production at the Large Hadron Collider.
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.
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.
INSTITUTE COLLOQUIA AND SEMINARS
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Quark-Gluon Plasma in pp Collision at LHC? April 28 Professor Wolfgang Mittig, NSCL, Michigan State University, East Lansing, Michigan Nuclear Power and Global Energy Problems...
Nuclear and Particle Physics, Astrophysics, and Cosmology
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
(often as probes of fundamental physics) Nuclear Astrophysics (neutron stars, supernovae, nucleosynthesis,...) QCD and RHICLHC (quark-gluon plasma, jets and energy...
ABSTRACTS FOR PAPERS SUBMITTED
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
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...
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.
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.
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 $x\\sim 1$.
Rapidity evolution of gluon TMD from low to moderate x
I. Balitsky; A. Tarasov
2015-09-29T23:59:59.000Z
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 $x \\sim 1$.
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.
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.
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?
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.
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 $\\tan\\beta \\agt 10$.
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.
Simulations with dynamical HISQ quarks
A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Laiho; L. Levkova; M. Oktay; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water
2010-12-06T23:59:59.000Z
We report on the status of a program of generating and using configurations with four flavors of dynamical quarks, using the HISQ action. We study the lattice spacing dependence of physical quantities in these simulations, using runs at several lattice spacings, but with the light quark mass held fixed at two tenths of the strange quark mass. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses. We also discuss methods for setting the scale, or assigning a lattice spacing to ensembles run at unphysical parameters.
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.
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, D80805 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.
Cold quark matter in compact stars
Franzon, B.; Fogaca, D. A.; Navarra, F. S. [Instituto de Fisica, Universidade de Sao Paulo Rua do Matao, Travessa R, 187, 05508-090 Sao Paulo, SP (Brazil); Horvath, J. E. [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao, 1226, 05508-090, Sao Paulo, SP (Brazil)
2013-03-25T23:59:59.000Z
We used an equation of state for the cold quark matter to the study of properties of quark stars. We also discuss the absolute stability of quark matter and compute the mass-radius relation for self-bound stars.
Heavy Quark production at HERA and Heavy Quark contributions
Detlef Bartsch, University of Bonn on behalf of the ZEUS and H1 Collaborations Ā· Introduction Ā· 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
Gluon mass and freezing of the QCD coupling
A. C. Aguilar; J. Papavassiliou
2007-11-06T23:59:59.000Z
Infrared finite solutions for the gluon propagator of pure QCD are obtained from the gauge-invariant non-linear Schwinger-Dyson equation formulated in the Feynman gauge of the background field method. These solutions may be fitted using a massive propagator, with the special characteristic that the effective mass employed drops asymptotically as the inverse square of the momentum transfer, in agreement with general operator-product expansion arguments. Due to the presence of the dynamical gluon mass the strong effective charge extracted from these solutions freezes at a finite value, giving rise to an infrared fixed point for QCD.
Experimental studies of unbiased gluon jets from e^+e^? annihilations using the jet boost algorithm
Wilson, Graham Wallace; Abbiendi, G.; Ainsley, C.; Å kesson, P. F.; Alexander, G.; Allison, J.; Amaral, P.; Anagnostou, G.; Anderson, K.J.; Arcelli, S.; Asai, S.; Axen, D.; Azuelos, G.; Bailey, I.; Barberio, E.
2004-02-25T23:59:59.000Z
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 ...
Higgs-boson production through gluon fusion at NNLO QCD with...
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Higgs-boson production through gluon fusion at NNLO QCD with parton showers Citation Details In-Document Search Title: Higgs-boson production through gluon fusion at NNLO QCD with...
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}.
Quantum Collapse in Quark Stars?
Perez Martinez, A.; Perez Rojas, H. [ICIMAF, Calle E esq 15 No. 309 Vedado (Cuba); Mosquera Cuesta, H. J. [Centro Brasileiro de Pesquisas Fisicas, Laboratorio de Cosmologia e Fisica Experimental de Altas Energias, Rua Dr. Xavier Sigaud 150, Urca, CEP 22290-180, Rio de Janeiro (Brazil)
2006-06-19T23:59:59.000Z
Quark matter is expected to exist in the interior of compact stellar objects as neutron stars or even the more exotic strange stars. Bare strange quark stars and (normal) strange quark-matter stars, those possessing a baryon (electron-supported) crust, are hypothesized as good candidates to explain the properties of a set of peculiar stellar sources. In this presentation, we modify the MIT Bag Model by including the electromagnetic interaction. We also show that this version of the MIT model implies the anisotropy of the Bag pressure due to the presence of the magnetic field. The equations of state of degenerate quarks gases are studied in the presence of ultra strong magnetic fields. The behavior of a system made-up of quarks having (or not) anomalous magnetic moment is reviewed. A structural instability is found, which is related to the anisotropic nature of the pressures in this highly magnetized matter.
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.
Leading soft gluon production in high energy nuclear collisions
Xiaofeng Guo
1999-02-23T23:59:59.000Z
The leading soft gluon p_T distribution in heavy ion collisions was obtained by Kovner, McLerran, and Weigert after solving classical Yang-Mills equations. I show explicitly this result can be understood in terms of conventional QCD perturbation theory. I also demonstrate that the key logarithm in their result represents the logarithm in DGLAP evolution equations.
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.
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.
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.
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.
Color structure for soft gluon resummation - a general recipe
Malin Sjodahl
2009-07-31T23:59:59.000Z
A strategy for calculating the color structure needed for soft gluon resummation for processes with any number of colored partons is introduced using a N_c --> infinity inspired basis. In this basis a general formalism can be found at the same time as the calculations are simplified. The advantages are illustrated by recalculating the soft anomalous dimension matrix for the processes gg --> gg, q\\qbar --> q \\qbar g and q\\qbar --> ggg.
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.
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.
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.
Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange
Llanes-Estrada, Felipe J; Swanson, Eric S; Szczepaniak, Adam P; Llanes-Estrada, Felipe J.; Cotanch, Stephen R.; Szczepaniak, Adam P.; Swanson, Eric S.
2004-01-01T23:59:59.000Z
Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both $S$ and $D$ waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the $\\pi$-$\\rho$ mass difference. A good, consistent description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the $\\pi$ mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The $\\eta_b$ mass is predicted to be around 9400 MeV consistent w...
Nuclear Matter with Relativistic Quark Dynamics
Suisso, E.F.; Batista, E.F.; Araujo, W.R.B. de; Frederico, T.; Carlson, B.V. [Dep. de Fisica, Instituto Tecnologico da Aeronautca, Centro Tecnico Aeroespacial, 12.228-901, Sao Jose dos Campos, Sao Paulo (Brazil)
2004-12-02T23:59:59.000Z
We investigate a quark-meson coupling model of the nuclear matter with a light-front nucleon model, where the quarks interact with flavor independent contact force. We found results comparable to the ones obtained with a confining interaction.
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.
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 ...
Top Quark Production at the LHC
Francesco Spanņ; 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.
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
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.
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.
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.
Non-Perturbative Corrections to Heavy Quark Fragmentation in e^+e^- Annihilation
P. Nason; B. R. Webber
1996-12-13T23:59:59.000Z
We estimate the non-perturbative power-suppressed corrections to heavy flavour fragmentation and correlation functions in e^+e^- annihilation, using a model based on the analysis of one-loop Feynman graphs containing a massive gluon. This approach corresponds to the study of infrared renormalons in the large-n_f limit of QCD, or to the assumption of an infrared-finite effective coupling at low scales. We find that the leading corrections to the heavy quark fragmentation function are of order $\\lambda/M$, where $\\lambda$ is a typical hadronic scale ($\\lambda\\sim 0.4$ GeV) and M is the heavy quark mass. The inclusion of higher corrections corresponds to convolution with a universal function of M(1-x) concentrated at values of its argument of order $\\lambda$, in agreement with intuitive expectations. On the other hand, corrections to heavy quark correlations are very small, of the order of $(\\lambda/Q)^p$, where Q is the centre-of-mass energy and $p \\ge 2$.
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.
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...
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. GoĀ“mez,5 G. GoĀ“mez
Three lectures on the physics of small x and high gluon density
McLerran, Larry [Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
1999-10-25T23:59:59.000Z
In these lectures, I shall discuss small x physics and the consequences of the high gluon density which arises as x decreases. I argue that an understanding of this problem would lead to knowledge of the high energy asymptotics of hadronic processes. The high gluon density should allow a first principles computation of these asymptotics from QCD.
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.
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.
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...
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.
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.
Hershcovitch, Ady (Mount Sinai, NY); Sharma, Sushil (Hinsdale, IL); Noonan, John (Naperville, IL); Rotela, Elbio (Clarendon Hills, IL); Khounsary, Ali (Hinsdale, IL)
2003-01-01T23:59:59.000Z
A plasma valve includes a confinement channel and primary anode and cathode disposed therein. An ignition cathode is disposed adjacent the primary cathode. Power supplies are joined to the cathodes and anode for rapidly igniting and maintaining a plasma in the channel for preventing leakage of atmospheric pressure through the channel.
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 properties at the Tevatron
Andreas Werner Jung
2014-12-12T23:59:59.000Z
Recent measurements of top-quark properties at the Tevatron, including top quark production asymmetries and properties, are presented. Latest updates of measurements of top quark production asymmetries include the measurement of the $t\\bar{t}$ production asymmetry by D0 employing the full Run II data set, in the lepton + jets and dilepton decay channel. Within their uncertainties the results from all these measurements agree with their respective Standard Model expectation.
Detecting Fourth Generation Quarks at Hadron Colliders
David Atwood; Sudhir Kumar Gupta; Amarjit Soni
2011-07-13T23:59:59.000Z
We consider the phenomenology of the fourth generation heavy quarks which would be pair produced at the LHC. We show that if such a quark with a mass in the phenomenologically interesting range of 400 GeV--600 GeV decays to a light quark and a W-boson, it will produce a signal in a number of channels which can be seen above the background from the three generation Standard Model processes. In particular, such quarks could be seen in channels where multiple jets are present with large missing momentum and either a single hard lepton, an opposite sign hard lepton pair or a same sign lepton pair. In the same sign dilepton channel there is little background and so an excess of such pairs at large invariant mass will indicate the presence of heavy down type quarks. More generally, in our study, the main tool we use to determine the mass of the heavy quark in each of the channels we consider is to use the kinematics of the decay of such quarks to resolve the momenta of the unobserved neutrinos. We show how this can be carried out, even in cases where the kinematics is under-determined by use of the approximation, which holds quite well, that the two heavy quarks are nearly at rest in the center of mass frame. Since it is very likely that at least the lightest heavy quark decays in the mode we consider, this means that it should be observed at the LHC. Indeed, it is expected that the mass splitting between the quarks is less than $m_W$ so that if the Cabbibo-Kobayshi-Maskawa (CKM) matrix element between the fourth and lower generations are not too small, both members of the fourth generation quark doublet will decay in this way. If this is so, the combined signal of these two quarks will make the signal for the fourth generation somewhat more prominent.
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
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 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.
Zhang, Guang-Peng
2015-01-01T23:59:59.000Z
The back-to-back $J/\\psi$ and $\\pi$ associated production at $e^+ e^-$ colliders is proposed to detect the gluon transverse momentum dependent(TMD) fragmentation functions. TMD factorization is assumed for this process. With spinless pion, unpolarized and linearly polarized gluon TMD fragmentation functions can be defined. It is found at parton level the hadronic tensor can be described by four structure functions. As a result, there are three independent angular distributions, of which a $\\cos{2\\phi}$ azimuthal asymmetry is sensitive to the linearly polarized gluon fragmentation function.
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.
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.
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.
A measurement of the top quark's charge
Unalan, Zeynep Gunay; /Michigan State U.
2007-11-01T23:59:59.000Z
The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative 'exotic' model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using {approx} 1 fb{sup -1} of data. The data were collected by the CDF detector from proton anti-proton (p{bar p}) collisions at {radical}s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear 'SM-like' or 'exotic-like' with a SM-like event decaying as t {yields} W{sup +}b and an exotic event as t {yields} W{sup -}b. We find the p-value under the Standard Model hypothesis to be 0:35 which is consistent with the Standard Model. We exclude the exotic quark hypothesis at an 81% confidence level, for which we have chosen a priori that the probability of incorrectly rejecting the SM would be 1%. The calculated Bayes Factor (BF) is 2 x Ln(BF)=8.54 which is interpreted as the data strongly favors the Standard Model over the exotic quark hypothesis.
D-meson enhancement in pp collisions at the LHC due to nonlinear gluon evolution
Dainese, A.; Vogt, R.; Bondila, M.; Eskola, K.J.; Kolhinen, V.J.
2004-08-22T23:59:59.000Z
When nonlinear effects on the gluon evolution are included with constraints from HERA, the gluon distribution in the free proton is enhanced at low momentum fractions, x {approx}< 0.01, and low scales, Q{sup 2} {approx}< 10 GeV{sup 2}, relative to standard, DGLAP-evolved, gluon distributions. Consequently, such gluon distributions can enhance charm production in pp collisions at center of mass energy 14 TeV by up to a factor of five at midrapidity, y {approx} 0, and transverse momentum p{sub T} {yields} 0 in the most optimistic case. We show that most of this enhancement survives hadronization into D mesons. Assuming the same enhancement at leading and next-to-leading order, we show that the D enhancement may be measured by D{sup 0} reconstruction in the K{sup -}{pi}{sup +} decay channel with the ALICE detector.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Gluon saturation and Feynman scaling in leading neutron production
Carvalho, F; Spiering, D; Navarra, F S
2015-01-01T23:59:59.000Z
In this paper we extend the color dipole formalism to the study of leading neutron production in $e + p \\rightarrow e + n + X$ collisions at high energies and estimate the related observables, which were measured at HERA and may be analysed in future electron-proton ($ep$) colliders. In particular, we calculate the Feynman $x_F$ distribution of leading neutrons, which is expressed in terms of the pion flux and the photon-pion total cross section. In the color dipole formalism, the photon-pion cross section is described in terms of the dipole-pion scattering amplitude, which contains information about the QCD dynamics at high energies and gluon saturation effects. We consider different models for the scattering amplitude, which have been used to describe the inclusive and diffractive $ep$ HERA data. Moreover, the model dependence of our predictions with the description of the pion flux is analysed in detail. We show that the recently released H1 leading neutron spectra can be reproduced using the color dipole ...
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.
Systematic Studies of Jet Quenching in Hot Nuclear Matter
Delgado, Andrea
2011-05-04T23:59:59.000Z
The early universe was filled with a primordial form of matter called Quark Gluon Plasma that only exists at extremely high temperatures and densities, many times hotter than the core temperature of suns. By colliding heavy nuclei at top energies...
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.
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.
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....
XLV International Winter Meeting on Nuclear Physics BORMIO, Italy, January 14-21, 2007
Paris-Sud XI, UniversitĆ© 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
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...
Mueller, B.; Springer, R.P.
1994-05-15T23:59:59.000Z
This report briefly discusses the following topics: quark-gluon plasma and high-energy collisions; hadron structure and chiral dynamics; nonperturbative studies and nonabelian gauge theories; and studies in quantum field theory.
Inserting Group Variables into Fluid Mechanics
R. Jackiw
2004-10-28T23:59:59.000Z
A fluid, like a quark-gluon plasma, may possess degrees of freedom indexed by a group variable, which retains its identity even in the fluid/continuum description. Conventional Eulerian fluid mechanics is extended to encompass this possibility.
STAR Heavy Flavor Tracker Detects Signs of Charm at RHIC | U...
Office of Science (SC) Website
of properties of the quark-gluon plasma and will stimulate new theoretical studies. The energy deposited when RHIC collides gold ions at nearly the speed of light creates...
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.
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.
Search for Fourth Generation Quarks at CMS
Michael M. H. Luk
2011-10-26T23:59:59.000Z
We summarise the analyses that search for fourth generation quarks at the Central Muon Solenoid (CMS) experiment. Such particles provide a natural extension to the Standard Model (SM) and are still consistent with precision electroweak measurements. Our searches are not limited to fourth generation chiral quarks and are relevant to many Beyond the Standard Model theories. No excess over the expected SM background is observed in any of these analyses and limits are set on the masses of the $b^\\prime$ and $t^\\prime$ quarks at 95% confidence level at 361 GeV/$c^2$ and 450 GeV/$c^2$, respectively.
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.
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.
Static strings in Randall-Sundrum scenarios and the quark anti-quark potential: Erratum
Henrique Boschi-Filho; Nelson R. F. Braga; Cristine N. Ferreira
2006-10-11T23:59:59.000Z
We correct the energy of the static strings in hep-th/0512295, for large quark anti-quark separation. This energy is a smooth function of the quark separation for any position of the infrared brane. The asymptotic behavior of this energy is that of the Cornell potential as stated in the article. However, this identification does not fixes the AdS radius.
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.
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...
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.
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.
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.
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.
Collider signature of T-quarks
Carena, Marcela; Hubisz, Jay; /Fermilab; Perelstein, Maxim; /Cornell U., LEPP; Verdier, Patrice; /Lyon, IPN
2006-10-01T23:59:59.000Z
Little Higgs models with T Parity contain new vector-like fermions, the T-odd quarks or ''T-quarks'', which can be produced at hadron colliders with a QCD-strength cross section. Events with two acoplanar jets and large missing transverse energy provide a simple signature of T-quark production. We show that searches for this signature with the Tevatron Run II data can probe a significant part of the Little Higgs model parameter space not accessible to previous experiments, exploring T-quark masses up to about 400 GeV. This reach covers parts of the parameter space where the lightest T-odd particle can account for the observed dark matter relic abundance. We also comment on the prospects for this search at the Large Hadron Collider (LHC).
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.
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.
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).
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Laser Plasma Interactions Laser Plasma Interactions Understanding and controlling laser produced plasmas for fusion and basic science Contact David Montgomery (505) 665-7994 Email...
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.
White, C D; Thorne, Robert S
) = ?S ? ? 0 dk2 k2 hi(k2/Q2)f(N, k2, Q20)gB(N,Q 2 0), (1) where gB is the bare gluon distribution at momentum scale Q20, and the strong coupling ?S is fixed at LL order. The hi(k2/Q2) are the impact factors coupling the virtual photon to the gluon... )gB(N,Q 2 0), (2) which serves to define the impact factor h2. In a general factorisation scheme, one loses the simple inter- pretation of h2 as the coefficient function relating the gluon distribution to the structure function. Instead it represents...
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
Gluon saturation and pseudo-rapidity distributions of charged hadrons at RHIC energy regions
Xin-Bin Wei; Sheng-Qin Feng
2014-11-20T23:59:59.000Z
We modified the gluon saturation model by rescaling the momentum fraction according to saturation momentum and introduced the Cooper-Frye hydrodynamic evolution to systematically study the pseudo-rapidity distributions of final charged hadrons at different energies and different centralities for Au-Au collisions in relativistic heavy-ion collisions at BNL Relativistic Heavy Ion Collider (RHIC). The features of both gluon saturation and hydrodynamic evolution at different energies and different centralities for Au-Au collisions are investigated in this paper.
Gluon Sivers Function and Single Spin Asymmetry in $e+p^\\uparrow \\rightarrow e+J/\\psi + X$
Godbole, Rohini M; Mukherjee, Asmita; Rawoot, Vaibhav S
2012-01-01T23:59:59.000Z
We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/\\psi $ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies.
Gluon Sivers Function and Single Spin Asymmetry in $e+p^\\uparrow \\rightarrow e+J/?+ X$
Rohini M. Godbole; Anuradha Misra; Asmita Mukherjee; Vaibhav S. Rawoot
2012-10-03T23:59:59.000Z
We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/\\psi $ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies.
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.
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:1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level:5(Million Cubic Feet) Oregon (Including Vehicle Fuel) (Million Cubic Feet)sets safety record |PersonalPhotos Browse ByPlasma Camp December 12,38 (1996)4
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.
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.
Physics Beyond the Single Top Quark Observation
Heinson, A.P.; Collaboration, for the DZero
2010-10-01T23:59:59.000Z
In March 2009, the D0 Collaboration first observed the electroweak production of single top quarks at 5{sigma} significance. We measured the cross section for the combined s-channel and t-channel production modes, and set a lower limit on the CKM matrix element |V{sub tb}|. Since then, we have used the same dataset to measure the t-channel production mode independently, the combined cross section in the hadronically-decaying tau lepton final state, and the width and lifetime of the top quark, and we have set upper limits on contributions from anomalous flavor-changing neutral currents. This paper describes these new measurements, as presented at the 3rd International Workshop on Top Quark Physics, held in Brugge, Belgium, May 31-June 4, 2010.
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.
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.
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.
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.
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.
Jorgen D'hondt
2007-07-10T23:59:59.000Z
The Large Hadron Collider (LHC) is expected to provide proton-proton collisions at a centre-of-mass energy of 14 TeV, yielding millions of of top quark events. The top-physics potential of the two general purpose experiments, ATLAS and CMS, is discussed according to state-of-the-art simulation of both physics and detectors. An overview is given of the most important results with emphasis on the expected improvements in our understanding of physics connected to the top quark.
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.
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.
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.
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
On static quark anti-quark potential at non-zero temperature
A. Bazavov; P. Petreczky
2012-10-23T23:59:59.000Z
We study Wilson loops at non-zero temperature and extract the static quark potential from them. The extracted potentials are larger than the singlet free energies and do not show screening for $T<190$ MeV.
Heavy-quark symmetry and chiral dynamics
Yan, T. (Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (Taiwan, Province of China) Floyd R. Newman Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853 (United States)); Cheng, H.; Cheung, C.; Lin, G. (Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (Taiwan, Province of China)); Lin, Y.C. (Physics Department, National Central University, Chung-li, Taiwan 32054 (Taiwan, Province of China)); Yu, H. (Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (Taiwan, Province of China))
1992-08-01T23:59:59.000Z
The flavor and spin symmetry of the heavy quarks and the spontaneously broken approximate SU(3){sub {ital L}}{times} SU(3){sub {ital R}} chiral symmetry of the light quarks are exploited to formulate a theory describing the low-energy interactions of the heavy mesons ({ital Q{bar q}} bound states) and heavy baryons ({ital Qq}{sub 1}{ital q2} bound states) with the Goldstone bosons {pi}, {ital K}, and {eta}. The theory contains only three parameters independent of the number of heavy-quark species involved. They can be determined by the decays {ital D}{sup *}{r arrow}{ital D}+{pi}, {Sigma}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}+{pi}, and {Sigma}{sub {ital c}}{sup *}{r arrow}{Sigma}{sub {ital c}}+{pi}. Theoretically, these coupling constants are related, through partial conservation of axial-vector current, to the axial charges of the heavy mesons and the heavy baryons. They are all calculable in the nonrelativistic quark model by using the spin wave functions of these particles alone. The theory is applied to strong decays and semileptonic weak decays of the heavy mesons and baryons. The implications are also discussed.
Diquark and light four-quark states
Zhang Ailin [Department of Physics, Shanghai University, Shanghai, 200444 (China); Huang Tao [Institute of High Energy Physics, Chinese Academy of Science, P. O. Box 918 (4), Beijing, 100049 (China); Steele, Tom G. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SK, S7N 5E2 (Canada)
2007-08-01T23:59:59.000Z
Four-quark states with different internal clusters are discussed within the constituent quark model. It is pointed out that the diquark concept is not meaningful in the construction of a tetraquark interpolating current in the QCD sum-rule approach, and hence existing sum-rule studies of four-quark states are incomplete. An updated QCD sum-rule determination of the properties of diquark clusters is then used as input for the constituent quark model to obtain the masses of light 0{sup ++} tetraquark states (i.e. a bound state of two diquark clusters). The results support the identification of {sigma}(600), f{sub 0}(980), and a{sub 0}(980) as the 0{sup ++} light tetraquark states, and seem to be inconsistent with the tetraquark state interpretation of the new BES observations of the near-threshold pp enhancements, X(1835) and X(1812), with the possible exception that X(1576) may be an exotic first orbital excitation of f{sub 0}(980) or a{sub 0}(980)
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.
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.
Effective Field Theory for Top Quark Physics
Cen Zhang; Scott Willenbrock
2010-08-18T23:59:59.000Z
Physics beyond the standard model can affect top-quark physics indirectly. We describe the effective field theory approach to describing such physics, and contrast it with the vertex-function approach that has been pursued previously. We argue that the effective field theory approach has many fundamental advantages and is also simpler.
B-physics with dynamical domain-wall light quarks and relativistic b-quarks
Ruth S. Van de Water; Oliver Witzel
2011-01-24T23:59:59.000Z
We report on our progress in calculating the B-meson decay constants and B^0-bar B^0 mixing parameters using domain-wall light quarks and relativistic b-quarks. We present our computational method and show some preliminary results obtained on the coarser (a approx 0.11fm) 24^3 lattices. This work is presented on behalf of the RBC and UKQCD collaborations.
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.
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
C. G. Duan; N. Liu; G. L. Li
2008-11-05T23:59:59.000Z
By means of two different parametrizations of quark energy loss and the nuclear parton distributions determined only with lepton-nuclear deep inelastic scattering experimental data, a leading order phenomenological analysis is performed on the nuclear Drell-Yan differential cross section ratios as a function of the quark momentum fraction in the beam proton and target nuclei for E772 experimental data. It is shown that there is the quark energy loss effect in nuclear Drell-Yan process apart from the nuclear effects on the parton distribution as in deep inelastic scattering. The uncertainties due to quark energy loss effect is quantified on determining nuclear sea quark distribution by using nuclear Drell-Yan data. It is found that the quark energy loss effect on nuclear Drell-Yan cross section ratios make greater with the increase of quark momentum fraction in the target nuclei. The uncertainties from quark energy loss become bigger as the nucleus A come to be heavier. The Drell-Yan data on proton incident middle and heavy nuclei versus deuterium would result in an overestimate for nuclear modifications on sea quark distribution functions with neglecting the quark energy loss. Our results are hoped to provide good directional information on the magnitude and form of nuclear modifications on sea quark distribution functions by means of the nuclear Drell-Yan experimental data.
Free energies of heavy quarks in full-QCD lattice simulations with Wilson-type quark action
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya; H. Ohno; T. Umeda
2009-09-16T23:59:59.000Z
The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature in lattice QCD with 2+1 flavors of improved Wilson quarks. From the simulations on $32^3 \\times 12$, 10, 8, 6, 4 lattices in the high temperature phase, based on the fixed scale approach, we find that, the heavy-quark free energies at short distance converge to the heavy-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 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 free energy is compared with the results of thermal perturbation theory.
S. G. Matinyan; B. Mueller; D. H. Rischke
1997-08-28T23:59:59.000Z
We investigate the space-time structure of the classical gluon field produced in an ultrarelativistic collision between color charges. The classical solution which was computed previously in a perturbative approach is shown to become unstable on account of the non-Abelian self-interaction neglected in the perturbative solution scheme. The time scale for growth of the instabilities is found to be of the order of the distance between the colliding color charges. We argue that these instabilities will eventually lead to thermalization of gluons produced in an ultrarelativistic collision between heavy nuclei. The rate of thermalization is estimated to be of order $g^2 \\mu$, where $g$ is the strong coupling constant and $\\mu^2$ the transverse color charge density of an ultrarelativistic nucleus.
Higgs boson as a gluon trigger: the study of QCD in high pile-up environments
H. Van Haevermaet; P. Cipriano; S. Dooling; A. Grebenyuk; P. Gunnellini; F. Hautmann; H. Jung; P. Katsas
2014-07-10T23:59:59.000Z
In the forthcoming high-luminosity phase of the LHC many of the most interesting measurements for precision QCD studies are hampered by large pile-up conditions, especially at not very high transverse momenta. However, with the recently discovered Higgs boson, which couples in the heavy top limit directly to gluons, we have access to a novel production process to probe QCD by a colour-singlet current. In this study we compare observables in Higgs boson and Drell-Yan production and investigate whether measuring ratios or subtractions can yield results that are stable in high pile-up environments, and yet sensitive to (small-$p_{\\text{T}}$) QCD physics in gluon fusion processes. We present results of Monte Carlo event generator calculations for a few specific examples.
Bootstrapping six-gluon scattering in planar ${\\cal N}=4$ super-Yang-Mills theory
Lance J. Dixon; James M. Drummond; Claude Duhr; Matt von Hippel; Jeffrey Pennington
2014-07-25T23:59:59.000Z
We describe the hexagon function bootstrap for solving for six-gluon scattering amplitudes in the large $N_c$ limit of ${\\cal N}=4$ super-Yang-Mills theory. In this method, an ansatz for the finite part of these amplitudes is constrained at the level of amplitudes, not integrands, using boundary information. In the near-collinear limit, the dual picture of the amplitudes as Wilson loops leads to an operator product expansion which has been solved using integrability by Basso, Sever and Vieira. Factorization of the amplitudes in the multi-Regge limit provides additional boundary data. This bootstrap has been applied successfully through four loops for the maximally helicity violating (MHV) configuration of gluon helicities, and through three loops for the non-MHV case.
On P_T-distribution of gluon production rate in constant chromoelectric field
D. G. Pak
2007-02-22T23:59:59.000Z
A complete expression for the p_T-distribution of the gluon production rate in the homogeneous chromoelectric field has been obtained. Our result contains a new additional term proportional to the singular function \\delta(p_T^2). We demonstrate that the presence of this term is consistent with the dual symmetry of QCD effective action and allows to reproduce the known result for the total imaginary part of the effective action after integration over transverse momentum.
Asymptotic freedom and IR freezing in QCD: the role of gluon paramagnetism
Yu. A. Simonov
2010-11-24T23:59:59.000Z
Paramagnetism of gluons is shown to play the basic role in establishing main properties of QCD: IR freezing and asymptotic freedom (AF). Starting with Polyakov background field approach the first terms of background perturbation theory are calculated and shown to ensure not only the classical result of AF but also IR freezing. For the latter only the confining property of the background is needed, and the effective mass entering the IR freezing logarithms is calculated in good agreement with phenomenology and lattice data.
The high-energy limit of H+2 jet production via gluon fusion
V. Del Duca; W. B. Kilgore; C. Oleari; C. R. Schmidt; D. Zeppenfeld
2002-03-16T23:59:59.000Z
We consider Higgs + 2 jet production via gluon fusion in the limit where either one of the Higgs-jet or the dijet invariant masses become much larger than the typical momentum transfers in the scattering. These limits also occur naturally in Higgs production via weak-boson fusion. We show that the scattering amplitudes factorize in the high energy limit, and we obtain the relevant effective vertices.
Measuring the Gluon Density in e + A Collisions: KLN CGC, DGLAP Glauber, or Neither?
W. A. Horowitz
2011-02-24T23:59:59.000Z
We predict readily experimentally measurable differences in the diffractive cross section in the coherent exclusive photoproduction of J/psi mesons in e + A collisions at eRHIC and LHeC energies for nuclear gluon distributions assumed to 1) evolve in x with DGLAP dynamics and have a spatial distribution proportional to the Glauber nuclear thickness function and 2) evolve in x and b according to the KLN prescription of CGC dynamics. We find that CGC physics predicts that the nuclear gluon density widens significantly as a function of x yielding diffractive peaks and minima that evolve dramatically with x; on the other hand the DGLAP Glauber distribution yields peaks and minima constant in x. We also find that the dipole cross section at the level of two gluon exchange within the KLN parameterization of the CGC satisfies the black disk limit whereas this limit is violated when DGLAP evolution is used; the normalization of the diffractive cross section grows more slowly in x by several orders of magnitude when using the KLN parameterization as compared to the result when employing DGLAP evolution.
Measuring the Gluon Density in e + A Collisions: KLN CGC, DGLAP Glauber, or Neither?
Horowitz, W A
2011-01-01T23:59:59.000Z
We predict readily experimentally measurable differences in the diffractive cross section in the coherent exclusive photoproduction of J/psi mesons in e + A collisions at eRHIC and LHeC energies for nuclear gluon distributions assumed to 1) evolve in x with DGLAP dynamics and have a spatial distribution proportional to the Glauber nuclear thickness function and 2) evolve in x and b according to the KLN prescription of CGC dynamics. We find that CGC physics predicts that the nuclear gluon density widens significantly as a function of x yielding diffractive peaks and minima that evolve dramatically with x; on the other hand the DGLAP Glauber distribution yields peaks and minima constant in x. We also find that the dipole cross section at the level of two gluon exchange within the KLN parameterization of the CGC satisfies the black disk limit whereas this limit is violated when DGLAP evolution is used; the normalization of the diffractive cross section grows more slowly in x by several orders of magnitude when u...
B-quark production at hadron colliders
Meng, Ruibin [Argonne National Lab., IL (United States); Riemersma, S. [Southern Methodist Univ., Dallas, TX (United States)
1993-08-01T23:59:59.000Z
Studying B-physics at hadron accelerators requires a good understanding of the total and differential cross sections for b-quark production. This knowledge gives those involved in B{bar B} mixing, rare B decays, and those trying to determine the CKM angles {alpha}, {beta}, and {gamma} an idea of how many events they can expect, given the luminosity and the branching ratios. It is particularly important for those studying rare B decays as they set limits on where we can hope to see new physics. For these reasons and others, the complete {Omicron}({alpha}{sub s}{sup 3}) corrections to heavy-quark production at hadron accelerators were calculated in. Also three groups have attempted to calculate heavy-quark production using resummation techniques in the small-x kinematic region. These resummation techniques are necessary since the b-quark mass m{sub b} is small relative to the center-of-mass energies {radical}S of the TeVatron and the SSC. While these techniques offer some hope of obtaining reasonable predictions for b-production at these machines, the current results can best be considered as preliminary. Thus we must turn to fixed-order perturbative QCD for guidance, as we have no other real choice at this point. However, let us submit a caveat here: fixed-order perturbative QCD works best when all the scales are roughly comparable, i.e. {radical}s {approx} m{sub b} {approx} p{sub t}, {radical}s being the partonic center-of-mass energy. When we are not in this regime, for example at the TeVatron and the SSC, our predictions will then be less reliable. Bearing this in mind, let use continue to the results section.
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
Color superconducting quark matter in compact stars
D. B. Blaschke; T. Klahn; F. Sandin
2007-12-02T23:59:59.000Z
Recent indications for high neutron star masses (M \\sim 2 M_sun) and large radii (R > 12 km) could rule out soft equations of state and have provoked a debate whether the occurence of quark matter in compact stars can be excluded as well. We show that modern quantum field theoretical approaches to quark matter including color superconductivity and a vector meanfield allow a microscopic description of hybrid stars which fulfill the new, strong constraints. For these objects color superconductivity turns out to be an essential ingredient for a successful description of the cooling phenomenology in accordance with recently developed tests. We discuss the energy release in the neutrino untrapping transition as a new aspect of the problem that hybrid stars masquerade themselves as neutron stars. Quark matter searches in future generations of low-temperature/high-density nucleus-nucleus collision experiments such as low-energy RHIC and CBM @ FAIR might face the same problem of an almost crossover behavior of the deconfinement transition. Therefore, diagnostic tools shall be derived from effects of color superconductivity.
Top quark physics at the Tevatron
Antonio Sidoti
2004-03-17T23:59:59.000Z
After the successful Run I of the Tevatron (1992-1996),with the top quark discovery, both CDF and D0 experiments were extensively upgraded to meet the challenges of the Tevatron Run II collider. The energy of p{bar p} collisions at the Tevatron was increased from {radical}s = 1.8 TeV to {radical}s = 1.96 TeV. t{bar t} production cross section is expected to increase by a factor of {approx} 30%. Major upgrades in the Tevatron accelerator chain will increase the Run II instantaneous luminosity: the goal is to achieve L = 5 - 20 x 10{sup 31} cm{sup 2}s{sup -1} while the highest luminosity reached up to now (September 2003) is 5.2 x 10{sup 31} cm{sup 2} s{sup -1}. In this paper we will present the top quark properties measured by both CDF and D0 with the first physics-quality data collected during the Run II (March 2002-January 2003). First we will review t{bar t} cross section measurements in the various decay channels; then top quark mass measurements will be presented.
The Top Quark - 2006 and Beyond
John Womersley
2006-04-04T23:59:59.000Z
We know there is new physics at the electroweak scale, but we don't know what it is. Right now, the top quark is our only window on to this physics. In almost all models of electroweak symmetry breaking, top either couples strongly to new particles or its properties are modified in some way. Top is being studied in detail at the Fermilab Tevatron. Its production cross section has been measured in a variety of channels; its mass has been determined to better than 2%, and can be used to constrain the mass of the Higgs. Top quark decays have been tested and non-standard production mechanisms searched for. Single top production probes the electroweak properties of top, and has not yet been observed; searches are now closing in on this process and it should be seen soon. So far, all of the top quark's properties are consistent with the Standard Model. However, the data still to come at the Tevatron will increase the precision of all these measurements, and the enormous statistics available at the LHC will open up new possibilities such as observation of spin correlations and perhaps even CP violation in the top sector.
Quark Nova Model for Fast Radio Bursts
Zachary Shand; Amir Ouyed; Nico Koning; Rachid Ouyed
2015-05-29T23:59:59.000Z
FRBs are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via $\\beta$-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm$^{-3}$ pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of $\\beta$-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies ($\\sim$ 10$^{41}$ ergs), spectra shapes and provide a theoretical framework for determining distances.
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.
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...
Top-quark mass measurements: Alternative techniques (LHC + Tevatron)
Stefanie Adomeit
2014-11-28T23:59:59.000Z
Measurements of the top-quark mass employing alternative techniques are presented, performed by the D0 and CDF collaborations at the Tevatron as well as the ATLAS and CMS experiments at the LHC. The alternative methods presented include measurements using the lifetime of $B$-hadrons, the transverse momentum of charged leptons and the endpoints of kinematic distributions in top quark anti-quark pair ($t\\bar{t}$) final states. The extraction of the top-quark pole mass from the $t\\bar{t}$ production cross-section and the normalized differential $t\\bar{t}$ + 1-jet cross-section are discussed as well as the top-quark mass extraction using fixed-order QCD predictions at detector level. Finally, a measurement of the top-quark mass using events enhanced in single top t-channel production is presented.
Static quark anti-quark pair in SU(2) gauge theory
A. Bazavov; P. Petreczky; A. Velytsky
2008-09-11T23:59:59.000Z
We study singlet and triplet correlation functions of static quark anti-quark pair defined through gauge invariant time-like Wilson loops and Polyakov loop correlators in finite temperature SU(2) gauge theory. We use the Luescher-Weisz multilevel algorithm, which allows to calculate these correlators at very low temperatures. We observe that the naive separation of singlet and triplet states in general does not hold non-perturbatively, however, is recovered in the limit of small separation and the temperature dependence of the corresponding correlators is indeed very different.
Top quark mass measurements at the D0 experiment
Alexander Grohsjean
2009-05-30T23:59:59.000Z
The most recent measurements of the top quark mass at the D0 experiment are summarized. Different techniques and final states are used and the top quark mass is determined to be mtop=172.8+-1.6(stat+syst)GeV/c^2. In addition, a new, indirect measurement comparing the measured cross section to theoretical calculations is discussed. Both, the direct and the indirect measurement of the top quark mass are in good agreement.
The Top Quark Forward Backward Asymmetry at CDF
Yen-Chu Chen for the CDF collaboration
2011-07-01T23:59:59.000Z
It has been more than 15 years since the discovery of the top quark. Great strides have been made in the measurement of the top quark mass and the properties of it. Most results show consistency with the standard model. However, using 5 fb$^{-1}$ data, recent measurements of the asymmetry in the production of top and anti-top quark pair have demonstrated surprisingly large values at CDF. Using 4 fb$^{-1}$ data, D0 also has similar effect.
Thermodynamics of QCD at large quark chemical potential
Andreas Gerhold; Andreas Ipp; Anton Rebhan
2005-12-21T23:59:59.000Z
We review the existing weak-coupling results on the thermodynamic potential of deconfined QCD at small and large quark chemical potential and compare with results from lattice gauge theory as well as the exactly solvable case of large-N_f QCD. We also discuss the new analytical results on non-Fermi-liquid effects in entropy and specific heat as well as in dispersion laws of quark quasiparticles at large quark chemical potential.
QCD Thermodynamics with an almost realistic quark mass spectrum
C. Schmidt
2006-01-25T23:59:59.000Z
We will report on the status of a new large scale calculation of thermodynamic quantities in QCD with light up and down quarks corresponding to an almost physical light quark mass value and a heavier strange quark mass. These calculations are currently being performed on the QCDOC Teraflops computers at BNL. We will present new lattice calculations of the transition temperature and various susceptibilities reflecting properties of the chiral transition. All these quantities are of immediate interest for heavy ion phenomenology.
Kirsch, Matthias; /Aachen, Tech. Hochsch.
2009-06-01T23:59:59.000Z
At particle accelerators the Standard Model has been tested and will be tested further to a great precision. The data analyzed in this thesis have been collected at the world's highest energetic-collider, the Tevatron, located at the Fermi National Accelerator Laboratory (FNAL) in the vicinity of Chicago, IL, USA. There, protons and antiprotons are collided at a center-of-mass energy of {radical}s = 1.96 TeV. The discovery of the top quark was one of the remarkable results not only for the CDF and D0 experiments at the Tevatron collider, but also for the Standard Model, which had predicted the existence of the top quark because of symmetry arguments long before already. Still, the Tevatron is the only facility able to produce top quarks. The predominant production mechanism of top quarks is the production of a top-antitop quark pair via the strong force. However, the Standard Model also allows the production of single top quarks via the electroweak interaction. This process features the unique opportunity to measure the |V{sub tb}| matrix element of the Cabbibo-Kobayashi-Maskawa (CKM) matrix directly, without assuming unitarity of the matrix or assuming that the number of quark generations is three. Hence, the measurement of the cross section of electroweak top quark production is more than the technical challenge to extract a physics process that only occurs one out of ten billion collisions. It is also an important test of the V-A structure of the electroweak interaction and a potential window to physics beyond the Standard Model in the case where the measurement of |V{sub tb}| would result in a value significantly different from 1, the value predicted by the Standard Model. At the Tevatron two production processes contribute significantly to the production of single top quarks: the production via the t-channel, also called W-gluon fusion, and the production via the s-channel, known as well as W* process. This analysis searches for the combined s+t channel production cross section, assuming the ratio of s-channel production over t-channel production is realized in nature as predicted by the Standard Model. A data set of approximately 1 fb{sup -1} is analyzed, the data set used by the D0 collaboration to claim evidence for single top quark production. Events with two, three, and four jets are used in the analysis if they contain one or two jets that were tagged as originating from the decay of a b hadron, an isolated muon or electron, and a significant amount of missing transverse energy. This selection of events follows the signature that the single top quark events are expected to show in the detector. In the meantime, both collaborations D0 and CDF have analyzed a larger data set and have celebrated the joint observation of single top quark production. The novelty of the analysis presented here is the way discriminating observables are determined. A so-called Multi-Process Factory evaluates each event under several hypotheses. A common analysis technique for example in top quark properties studies is to reconstruct the intermediate particles in the decay chain of the signal process from the final state objects measured in the various subdetectors. An essential part of such a method is to resolve the ambiguities that arise in the assignment of the final state objects to the partons of the decay chain. In a Multi-Process Factory this approach is extended and not only the decay chain of the signal process is reconstructed, but also the decay chains of the most important background processes. From the numerous possible event configurations for each of the signal and background decay chains the most probable configuration is selected based on a likelihood measure. Properties of this configuration, such as mass of the reconstructed top quark, are then used in a multivariate analysis technique to separate the expected signal contribution from the background processes. The technique which is used is called Boosted Decision Trees and has only recently been introduced in high energy physics analyses. A Bayesian approach is use
Evolution equation for 3-quark Wilson loop operator
R. E. Gerasimov; A. V. Grabovsky
2012-12-07T23:59:59.000Z
The evolution equation for the 3 quark Wilson loop operator has been derived in the leading logarithm approximation within Balitsky high energy operator expansion.
Proposal to support junior scientists participation of Quark Matter 2004
Huan Zhong Huang; Kenneth Barish; Hans Georg Ritter
2005-12-15T23:59:59.000Z
This report summarizes the student and post-doc support budget for quark matter 2004 conference, held at Oakland in January 2004.
Dynamical electroweak symmetry breaking and the top quark
Chivukula, R.S. [Boston Univ., MA (United States)
1997-01-01T23:59:59.000Z
In this talk, I discuss theories of dynamical electroweak symmetry breaking, with emphasis on the implications of a heavy top quark on the weak interaction {rho} parameter.
Light front approach to correlations in hot quark matter
S. Strauss; M. Beyer; S. Mattiello
2006-01-30T23:59:59.000Z
We investigate two-quark correlations in hot and dense quark matter. To this end we use the light front field theory extended to finite temperature $T$ and chemical potential $\\mu$. Therefore it is necessary to develop quantum statistics formulated on the light front plane. As a test case for light front quantization at finite $T$ and $\\mu$ we consider the NJL model. The solution of the in-medium gap equation leads to a constituent quark mass which depends on $T$ and $\\mu$. Two-quark systems are considered in the pionic and diquark channel. We compute the masses of the two-body system using a $T$-matrix approach.
Studies of top quark properties at the Tevatron
Shary, Viatcheslav
2012-05-01T23:59:59.000Z
An overview of the recent measurements of the top quark properties in proton antiproton collisions at {radical}s = 1.96 TeV is presented. These measurements are based on 5.4-8.7 fb{sup -1} of data collected with the D0 and CDF experiments at the Fermilab Tevatron collider. The top quark mass and width measurements, studies of the spin correlation in top quark pair production, W boson helicity measurement, searches for anomalous top quark couplings and Lorentz invariance violation are discussed.
Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya; N. Ukita; T. Umeda
2007-10-04T23:59:59.000Z
Thermodynamics of two-flavor QCD at finite temperature and density is studied on a $16^3 \\times 4$ lattice, using a renormalization group improved gauge action and the clover improved Wilson quark action. In the simulations along lines of constant $m_{\\rm PS}/m_{\\rm V}$, we calculate the Taylor expansion coefficients of the heavy-quark free energy with respect to the quark chemical potential ($\\mu_q$) up to the second order. By comparing the expansion coefficients of the free energies between quark($Q$)and antiquark($\\bar{Q}$), and between $Q$ and $Q$, we find a characteristic difference at finite $\\mu_q$ due to the first order coefficient of the Taylor expansion. We also calculate the quark number and isospin susceptibilities, and find that the second order coefficient of the quark number susceptibility shows enhancement around the pseudo-critical temperature.
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
Flavor Physics in the Quark Sector
Antonelli, Mario; /Frascati; Asner, David Mark; /Carleton U.; Bauer, Daniel Adams; /Imperial Coll., London; Becher, Thomas G.; /Fermilab; Beneke, M.; /Aachen, Tech. Hochsch.; Bevan, Adrian John; /Queen Mary, U. of London; Blanke, Monika; /Munich, Tech. U. /Munich, Max Planck Inst.; Bloise, C.; /Frascati; Bona, Marcella; /CERN; Bondar, Alexander E.; /Novosibirsk, IYF; Bozzi, Concezio; /INFN, Ferrara; Brod, Joachim; /Karlsruhe U.; Buras, Andrzej J.; /Munich, Tech. U.; Cabibbo, N.; /INFN, Rome /Rome U.; Carbone, A.; /INFN, Bologna; Cavoto, Gianluca; /INFN, Rome; Cirigliano, Vincenzo; /Los Alamos; Ciuchini, Marco; /INFN, Rome; Coleman, Jonathon P.; /SLAC; Cronin-Hennessy, Daniel P.; /Minnesota U.; Dalseno, J.P.; /KEK, Tsukuba /Glasgow U. /Queen Mary, U. of London /Freiburg U. /Charles U. /Pisa U. /Vienna, OAW /Imperial Coll., London /Bergen U. /INFN, Rome /Rome U. /Munich, Tech. U. /INFN, Rome /Rome U. /Southampton U. /INFN, Rome /Nara Women's U. /Florida U. /INFN, Turin /Turin U. /Edinburgh U. /Warwick U. /INFN, Rome /Rome U. /Massachusetts U., Amherst /KEK, Tsukuba /Bern U. /CERN /Munich, Tech. U. /Mainz U., Inst. Phys. /Wayne State U. /Munich, Max Planck Inst. /CERN /Frascati /Brookhaven /Mainz U., Inst. Kernphys. /Munich, Tech. U. /Siegen U. /Imperial Coll., London /Victoria U. /KEK, Tsukuba /Fermilab /Washington U., St. Louis /Frascati /Warwick U. /Indian Inst. Tech., Madras /Melbourne U. /Princeton U. /Beijing, Inst. High Energy Phys. /INFN, Rome /INFN, Rome3 /Fermilab /SLAC /York U., Canada /Brookhaven /UC, Irvine /INFN, Rome /Rome U. /Valencia U., IFIC /INFN, Padua /Padua U. /Munich, Max Planck Inst. /Barcelona U. /Warwick U. /Tata Inst. /Frascati /Mainz U., Inst. Phys. /Vienna U. /KEK, Tsukuba /Orsay, LPT /Frascati /Munich, Tech. U. /Brookhaven /Bern U. /CERN /Mainz U., Inst. Phys. /Wayne State U. /Valencia U., IFIC /CERN /Kentucky U. /Oxford U. /Iowa State U. /Bristol U. /INFN, Rome /Rutherford /CERN /Orsay, LAL /Glasgow U. /INFN, Padua /Queen Mary, U. of London /Texas U. /LPHE, Lausanne /Fermilab /UC, Santa Cruz /Vienna, OAW /Cincinnati U. /Frascati /Orsay, LAL /Ohio State U. /Purdue U. /Novosibirsk, IYF /Frascati /INFN, Rome /Padua U. /INFN, Rome /Bern U. /Karlsruhe U. /Brookhaven /CERN /Paris U., VI-VII /Zurich, ETH /Pisa U. /Frascati /Oxford U. /Orsay, LAL /INFN, Rome2 /INFN, Rome /INFN, Rome3 /Princeton U. /Fermilab /Queen's U., Kingston /KEK, Tsukuba /Melbourne U. /Brookhaven /Indiana U. /INFN, Rome /Rome U. /Pisa U. /Mainz U., Inst. Phys. /Karlsruhe U. /Oxford U. /Cambridge U., DAMTP /Edinburgh U. /CERN
2010-08-26T23:59:59.000Z
In the past decade, one of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor. In this time frame, measurements and the theoretical interpretation of their results have advanced tremendously. A much broader understanding of flavor particles has been achieved, apart from their masses and quantum numbers, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. In the past, observations of CP violation were confined to neutral K mesons, but since the early 1990s, a large number of CP-violating processes have been studied in detail in neutral B mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of K,D, and B mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments, thus a review of the status of quark flavor physics is timely. This report is the result of the work of the physicists attending the 5th CKM workshop, hosted by the University of Rome 'La Sapienza', September 9-13, 2008. It summarizes the results of the current generation of experiments that is about to be completed and it confronts these results with the theoretical understanding of the field which has greatly improved in the past decade.
Studies of top quark production at D0
Gerber, Cecilia E.; /Illinois U., Chicago
2011-07-01T23:59:59.000Z
I present recent results on top quark production in pp collisions at a center of mass energy of 1.96 TeV. The studies were performed by the D0 collaboration using approximately 5 fb{sup -1} of data taken during Run II at the Fermilab Tevatron accelerator. The top quark is the heaviest known elementary particle and completes the quark sector of the three-generation structure of the standard model (SM). It differs from the other quarks not only by its much larger mass, but also by its lifetime which is too short to build hadronic bound states. The SM predicts that top quarks are created via two independent production mechanisms at hadron colliders. The primary mode, in which a t{bar t} pair is produced from a gtt vertex via the strong interaction, was used by the D0 and CDF collaborations to establish the existence of the top quark in 1995. The second production mode of top quarks at hadron colliders is the electroweak production of a single top quark from a Wtb vertex. The predicted cross section for single top quark production is about half that of t{bar t} pairs but the signal-to-background ratio is much worse; observation of single top quark production has therefore until recently been impeded by its low rate and difficult background environment compared to the top pair production. In the following sections I will present results for the measurement of the t{bar t} pair and the single top quark production cross section using respectively 5.3 fb{sup -1} and 5.4 fb{sup -1} of data taken by the D0 experiment.
Top Quark Spin Correlations at the Tevatron
Head, Tim; /Manchester U.
2010-07-01T23:59:59.000Z
Recent measurements of the correlation between the spin of the top and the spin of the anti-top quark produced in proton anti-proton scattering at a center of mass energy of {radical}s = 1.96 Tev by the CDF and D0 collaborations are discussed. using up to 4.3 fb{sup -1} of data taken with the CDF and D0 detectors the spin correlation parameter C, the degree to which the spins are correlated, is measured in dileptonic and semileptonic final states. The measurements are found to be in agreement with Standard Model predictions.
Photon emission from bare quark stars
B. G. Zakharov
2010-08-16T23:59:59.000Z
We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures T\\sim 0.1-1 MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy for this mechanism is much larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair creation as well. We demonstrate that the LPM suppression of the photon emission is negligible.
Top quark mass measurements at the LHC
Fuster, Juan; The ATLAS collaboration
2015-01-01T23:59:59.000Z
The latest measurements of the top quark mass using the ATLAS and CMS experiments at the LHC are presented. The discussion includes the results obtained using the conventional methods (Template/Ideogram) and those derived from the so called alternative methods. Results from the conventional methods using the various top final states (lepton+jets, di-lepton and full hadronic) are reviewed. Determinations using the inclusive ttbar production, the ttbar production with an additional jet and the lepton-b-jet invariant mass distribution are also discussed.
Drag force in strongly coupled, anisotropic plasma at finite chemical potential
Somdeb Chakraborty; Najmul Haque
2014-10-26T23:59:59.000Z
We employ methods of gauge/string duality to analyze the drag force on a heavy quark moving through a strongly coupled, anisotropic \\mathcal{N}=4, SU(N) super Yang- Mills plasma in the presence of a finite U(1) chemical potential. We present numerical results valid for any value of the anisotropy parameter and the U(1) charge density and arbitrary direction of the quark velocity with respect to the direction of anisotropy. In the small anisotropy limit we are also able to furnish analytical results.
Ignatov, A.M. [Prokhorov Institute of General Physics, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991 (Russian Federation)
2005-01-15T23:59:59.000Z
The paper presents an introductory review of the basic physical processes in dusty plasmas. The topics to be addressed are dust charging, forces acting on dust grains, interaction between dust grains, and dust-plasma structures.
Higgs boson gluon-fusion production beyond threshold in N³LO QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
2015-03-01T23:59:59.000Z
In this article, we compute the gluon fusion Higgs boson cross-section at N³LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N³LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N³LO in perturbative QCD.
A manifestation of a gluon saturation in e-A DIS
Levin, E; Levin, Eugene; Maor, Uri
2000-01-01T23:59:59.000Z
This is a short presentation of our talks given at eRHIC Workshop at the BNL. We give here a status report of our attempts to understand how gluon saturation will manifest itself in deep inelastic scattering with nuclei. This summary reflects our current understanding and shows directions of our research rather then a final answer to the question. Nevertheless, we are able to share with our reader our tentative answer to the question:``Why do we need to measure DIS with nuclei and why these data will be complementary to the information obtained from proton DIS".
A manifestation of a gluon saturation in e-A DIS
Eugene Levin; Uri Maor
2000-09-19T23:59:59.000Z
This is a short presentation of our talks given at eRHIC Workshop at the BNL. We give here a status report of our attempts to understand how gluon saturation will manifest itself in deep inelastic scattering with nuclei. This summary reflects our current understanding and shows directions of our research rather then a final answer to the question. Nevertheless, we are able to share with our reader our tentative answer to the question:``Why do we need to measure DIS with nuclei and why these data will be complementary to the information obtained from proton DIS".
Higgs boson gluon-fusion production beyond threshold in N3LO QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Mistlberger, Bernhard
2015-03-01T23:59:59.000Z
In this article, we compute the gluon fusion Higgs boson cross-section at N3LO through the second term in the threshold expansion. This calculation constitutes a major milestone towards the full N3LO cross section. Our result has the best formal accuracy in the threshold expansion currently available, and includes contributions from collinear regions besides subleading corrections from soft and hard regions, as well as certain logarithmically enhanced contributions for general kinematics. We use our results to perform a critical appraisal of the validity of the threshold approximation at N3LO in perturbative QCD.
Single soft gluon emission at two loops (Journal Article) | SciTech Connect
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