Nuclear Physics from Lattice Quantum Chromodynamics
Savage, Martin J
2015-01-01T23:59:59.000Z
Quantum Chromodynamics and Quantum Electrodynamics, both renormalizable quantum field theories with a small number of precisely constrained input parameters, dominate the dynamics of the quarks and gluons - the underlying building blocks of protons, neutrons, and nuclei. While the analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they encounter difficulties when applied to low-energy nuclear structure and reactions, and dense systems. Expected increases in computational resources into the exascale during the next decade will provide the ability to determine a range of important strong interaction processes directly from QCD using the numerical technique of Lattice QCD. This will complement the nuclear physics experimental program, and in partnership with new thrusts in nuclear many-body theory, will enable unprecedented understanding and refinement of nuclear forces and, more generally, the visible matter in our universe. In th...
Resonances in Coupled ?K??K Scattering from Quantum Chromodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; Wilson, David J.
2014-10-01T23:59:59.000Z
Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled ?K, ?K scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.
Resonances in Coupled ?K-?K Scattering from Quantum Chromodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; Wilson, David J.
2014-10-01T23:59:59.000Z
Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled ?K, ?K scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.
Testing quantum chromodynamics in electroproduction
Brodsky, S.J.
1987-05-01T23:59:59.000Z
The exclusive channels in electroproduction are discussed. The study of color transparency, the formation zone, and other novel aspects of QCD by measuring exclusive reactions inside nuclear targets is covered. Diffractive electroproduction channels are discussed, and exclusive nuclear processes in QCD are examined. Non-additivity of nuclear structure functions (EMC effect) is also discussed, as well as jet coalescence in electroproduction. (LEW)
Quantum Electro and Chromodynamics treated by Thompson's heuristic approach
Claudio Nassif; P. R. Silva
2005-06-20T23:59:59.000Z
In this work we apply Thompson's method (of the dimensions and scales) to study some features of the Quantum Electro and Chromodynamics. This heuristic method can be considered as a simple and alternative way to the Renormalisation Group (R.G.) approach and when applied to QED-lagrangian is able to obtain in a first approximation both the running coupling constant behavior of alpha(mu) and the mass m(mu).The calculations are evaluated just at d_c=4, where d_c is the upper critical dimension of the problem, so that we obtain the logarithmic behavior both for the coupling alpha and the excess of mass Delta m on the energy scale mu. Although our results are well-known in the vast literature of field theories,it seems that one of the advantages of Thompson's method, beyond its simplicity is that it is able to extract directly from QED-lagrangian the physical (finite) behavior of alpha(mu) and m(mu), bypassing hard problems of divergences which normally appear in the conventional renormalisation schemes applied to field theories like QED. Quantum Chromodynamics (QCD) is also treated by the present method in order to obtain the quark condensate value. Besides this, the method is also able to evaluate the vacuum pressure at the boundary of the nucleon. This is done by assumming a step function behavior for the running coupling constant of the QCD, which fits nicely to some quantities related to the strong interaction evaluated through the MIT-bag model.
High Energy Resummation in Quantum Chromo–Dynamics
Marzani, Simone
2008-01-01T23:59:59.000Z
In this thesis I discuss different aspects of high energy resummation in Quantum Chromo-Dynamics and its relevance for precision physics at hadron colliders. The high energy factorisation theorem is presented and discussed ...
Resonances in coupled pi K, eta K scattering from quantum chromodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Dudek, Jozef J [JLAB; Edwards, Robert G [JLAB; Thomas, Christopher E; Wilson, David J
2014-10-01T23:59:59.000Z
Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled pi K, eta K scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.
On Flavor Symmetry in Lattice Quantum Chromodynamics
El Hassan Saidi
2012-03-27T23:59:59.000Z
Using a well established method to engineer non abelian symmetries in superstring compactifications, we study the link between the point splitting method of Creutz et al of refs [1,2] for implementing flavor symmetry in lattice QCD; and singularity theory in complex algebraic geometry. We show amongst others that Creutz flavors for naive fermions are intimately related with toric singularities of a class of complex Kahler manifolds that are explicitly built here. In the case of naive fermions of QCD$_{2N}$, Creutz flavors are shown to live at the poles of real 2-spheres and carry quantum charges of the fundamental of $[SU(2)]^{2N}$. We show moreover that the two Creutz flavors in Karsten-Wilczek model, with Dirac operator in reciprocal space of the form $i\\gamma_1 F_1+i\\gamma_2 F_2 + i\\gamma_3 F_3+\\frac{i}{\\sin \\alpha}\\gamma_4 F_4$, are related with the small resolution of conifold singularity that live at $\\sin \\alpha =0$. Other related features are also studied.
The CT14 Global Analysis of Quantum Chromodynamics
Sayipjamal Dulat; Tie Jiun Hou; Jun Gao; Marco Guzzi; Joey Huston; Pavel Nadolsky; Jon Pumplin; Carl Schmidt; Daniel Stump; C. P. Yuan
2015-08-02T23:59:59.000Z
We present new parton distribution functions (PDFs) up to next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged lepton rapidity asymmetry data, as well as the use of more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various $\\alpha_s$ values and additional sets in general-mass variable flavor number (GM-VFN) schemes, to deal with heavy partons, with up to 3, 4, and 6 active flavors.
The CT14 Global Analysis of Quantum Chromodynamics
Dulat, Sayipjamal; Gao, Jun; Guzzi, Marco; Huston, Joey; Nadolsky, Pavel; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C P
2015-01-01T23:59:59.000Z
We present new parton distribution functions (PDFs) up to next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged lepton rapidity asymmetry data, as well as the use of more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various $\\alpha_s$ values and additional sets in heavy-quark scheme with up to 3, 4, and 6 active flavors.
Non-perturbative Studies in Quantum Chromodynamics
Dipankar Chakrabarti
2004-03-22T23:59:59.000Z
In this thesis, two nonperturbative techniques, namely, similarity renormalization group (SRG) approach and light-front transverse lattice (LFTL) approach are studied in the the context of hadron bound state problem in light-front QCD. We first investigate the meson bound state problem in (2+1) dimensional QCD using Bloch effective Hamiltonian which serves as a benchmark for comparative study of the SRG Hamiltonian. In the SRG scheme we compare three different choices for the similarity factor. In (2+1) dimensions, in the lowest order, SRG produces linear confinement along the transverse direction but only square root confinement along the longitudinal direction and thus breaks the rotational symmetry. In the LFTL approach, we first investigate the problem associated with fermion formulation on a LFTL. When the symmetric lattice derivative is used, the doublers arise due to decoupling of even and odd sub-lattices. We have discussed Wilson fermion and staggered fermion to remove the doublers. We propose another way of formulating fermions on LFTL by using asymmetric lattice derivatives in such a way that the Hermiticity of the Hamiltonian is preserved. There are no doublers in this method. We also discuss the symmetry relevant for fermion doubling on LFTL. We also compare these two methods of fermion formulations in the context of meson bound state problem in (3+1) dimensional QCD with at most one link approximation.
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Nuclear Force from Monte Carlo Simulations of Lattice Quantum Chromodynamics
S. Aoki; T. Hatsuda; N. Ishii
2008-10-24T23:59:59.000Z
The nuclear force acting between protons and neutrons is studied in the Monte Carlo simulations of the fundamental theory of the strong interaction, the quantum chromodynamics defined on the hypercubic space-time lattice. After a brief summary of the empirical nucleon-nucleon (NN) potentials which can fit the NN scattering experiments in high precision, we outline the basic formulation to derive the potential between the extended objects such as the nucleons composed of quarks. The equal-time Bethe-Salpeter amplitude is a key ingredient for defining the NN potential on the lattice. We show the results of the numerical simulations on a $32^4$ lattice with the lattice spacing $a \\simeq 0.137 $fm (lattice volume (4.4 fm)$^4$) in the quenched approximation. The calculation was carried out using the massively parallel computer Blue Gene/L at KEK. We found that the calculated NN potential at low energy has basic features expected from the empirical NN potentials; attraction at long and medium distances and the repulsive core at short distance. Various future directions along this line of research are also summarized.
Light Nuclei and HyperNuclei from Quantum Chromodynamics in the Limit of SU(3) Flavor Symmetry
Beane, S R; Cohen, S D; Detmold, W; Lin, H W; Luu, T C; Orginos, K; Parreno, A; Savage, M J
2013-02-01T23:59:59.000Z
The binding energies of a range of nuclei and hypernuclei with atomic number A <= 4 and strangeness |s| <= 2, including the deuteron, di-neutron, H-dibaryon, {sup 3}He, {sub {Lambda}}{sup 3}He, {sub {Lambda}}{sup 4}He, and {sub {Lambda}{Lambda}}{sup 4}He, are calculated in the limit of flavor-SU(3) symmetry at the physical strange quark mass with quantum chromodynamics (without electromagnetic interactions). The nuclear states are extracted from Lattice QCD calculations performed with n{sub f}=3 dynamical light quarks using an isotropic clover discretization of the quark-action in three lattice volumes of spatial extent L ~ 3.4 fm, 4.5 fm and 6.7 fm, and with a single lattice spacing b ~ 0.145 fm.
Miransky, Vladimir A
2015-01-01T23:59:59.000Z
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chira...
Lattice Quantum Chromodynamics (SPI, mapping, site ordering, and QPX in
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Magnetic Moments of Light Nuclei from Lattice Quantum Chromodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Beane, S. R.; Chang, E.; Cohen, S.; Detmold, W.; Lin, H W.; Orginos, K.; Parreno, A; Savage, M J.; Tiburzi, B C.
2014-12-01T23:59:59.000Z
We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and 3He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to m_pi ~ 800 MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. In particular, we find that the magnetic moment of 3He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutron captures its dominant structure. Similarly a shell-model-like moment is found for the triton, mu_^3H ~ mu_p. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.
Magnetic Moments of Light Nuclei from Lattice Quantum Chromodynamics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Beane, S.? R.; Chang, E.; Cohen, S.; Detmold, W.; Lin, H.? W.; Orginos, K.; Parreño, A.; Savage, M.? J.; Tiburzi, B.? C.
2014-12-01T23:59:59.000Z
We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and 3He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to m? ~ 800 MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. In particular, we find that the magnetic moment of 3He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutronmore »captures its dominant structure. Similarly a shell-model-like moment is found for the triton, ?3H ~ ?p. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.« less
Vladimir A. Miransky; Igor A. Shovkovy
2015-04-10T23:59:59.000Z
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...
Adams, Allan
Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical and that do not have a simple description in terms of weakly interacting quasiparticles. Two systems that have recently ...
Haddad, Laith H
2015-01-01T23:59:59.000Z
We study superconductivity in the hadron-quark mixed phase of planar quantum chromodynamics within the large $N$ limit of a Gross-Neveu model modified by a repulsive vector term. At zero temperature, we find that reducing the quark density through a critical point destroys superconductivity via a Berezinskii-Kosterlitz-Thouless (BKT) phase transition. Dissolution of logarithmically bound diquarks is caused by chiral mixing in the quark field associated with $\\mathbb{Z}_2 \\otimes \\mathbb{Z}_2 \\to \\mathbb{Z}_2$ chiral symmetry breaking of the Fermi surface. We conjecture that a similar mechanism may underlie holographic BKT transitions.
Color transparency and the structure of the proton in quantum chromodynamics
Brodsky, S.J.
1989-06-01T23:59:59.000Z
Many anomalies suggest that the proton itself is 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-nontrivial 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-trivial 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. As we shall see in this lecture, the apparent discrepancies with experiment are not so much a failure of QCD, but rather symptoms of the complexity and richness of the theory. An important tool for analyzing this complexity is the light-cone Fock state representation of hadron wavefunctions, which provides a consistent but convenient framework for encoding the features of relativistic many-body systems in quantum field theory. 121 refs., 44 figs., 1 tab.
Studies in hadron structure using lattice QCD with quark masses that almost reach the physical point
Green, Jeremy Russell
2013-01-01T23:59:59.000Z
Lattice QCD allows us to study the structure of hadrons from first-principles calculations of quantum chromodynamics. We present calculations that shed light on the behavior of quarks inside hadrons in both qualitative and ...
Quantum chaos in QCD and hadrons
Harald Markum; Willibald Plessas; Rainer Pullirsch; Bianka Sengl; Robert F. Wagenbrunn
2005-05-13T23:59:59.000Z
This article is the written version of a talk delivered at the Workshop on Nonlinear Dynamics and Fundamental Interactions in Tashkent and starts with an introduction into quantum chaos and its relationship to classical chaos. The Bohigas-Giannoni-Schmit conjecture is formulated and evaluated within random-matrix theory. In accordance to the title, the presentation is twofold and begins with research results on quantum chromodynamics and the quark-gluon plasma. We conclude with recent research work on the spectroscopy of baryons. Within the framework of a relativistic constituent quark model we investigate the excitation spectra of the nucleon and the delta with regard to a possible chaotic behavior for the cases when a hyperfine interaction of either Goldstone-boson-exchange or one-gluon-exchange type is added to the confinement interaction. Agreement with predictions from the experimental hadron spectrum is established.
Brodsky, S.J.
1983-11-01T23:59:59.000Z
A number of novel features of QCD are reviewed, including the consequences of formation zone and color transparency phenomena in hadronic collisions, the use of automatic scale setting for perturbative predictions, null-zone phenomena as a fundamental test of gauge theory, and the relationship of intrinsic heavy colored particle Fock state components to new particle production. We conclude with a review of the applications of QCD to nuclear multiquark systems. 74 references.
Hyperon-Nucleon Interactions and the Composition of Dense Nuclear Matter from Quantum Chromodynamics
Beane, S R; Cohen, S D; Detmold, W; Lin, H -W; Luu, T C; Orginos, K; Parreno, A; Savage, M J
2012-10-01T23:59:59.000Z
The low-energy neutron-{Sigma}{sup -} interactions determine, in part, the role of the strange quark in dense matter, such as that found in astrophysical environments. The scattering phase shifts for this system are obtained from a numerical evaluation of the QCD path integral using the technique of Lattice QCD. Our calculations, performed at a pion mass of m{sub pi} ~ 389 MeV in two large lattice volumes, and at one lattice spacing, are extrapolated to the physical pion mass using effective field theory. The interactions determined from QCD are consistent with those extracted from hyperon-nucleon experimental data within uncertainties, and strengthen theoretical arguments that the strange quark is a crucial component of dense nuclear matter.
Hyperon-Nucleon Interactions and the Composition of Dense Nuclear Matter from Quantum Chromodynamics
S. R. Beane; E. Chang; S. D. Cohen; W. Detmold; H. -W. Lin; T. C. Luu; K. Orginos; A. Parreno; M. J. Savage; A. Walker-Loud
2012-04-16T23:59:59.000Z
The low-energy neutron-Sigma^- interactions determine, in part, the role of the strange quark in dense matter, such as that found in astrophysical environments. The scattering phase shifts for this system are obtained from a numerical evaluation of the QCD path integral using the technique of Lattice QCD. Our calculations, performed at a pion mass of m_pi ~ 389 MeV in two large lattice volumes, and at one lattice spacing, are extrapolated to the physical pion mass using effective field theory. The interactions determined from QCD are consistent with those extracted from hyperon-nucleon experimental data within uncertainties, and strengthen theoretical arguments that the strange quark is a crucial component of dense nuclear matter.
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.
Hyperon-Nucleon Interactions and the Composition of Dense Matter from Quantum Chromodynamics
Konstantinos Orginos, Silas Beane, Emmanuel Chang, Saul Cohen, Huey-Wen Lin, Tom Luu, Assumpta Parreno, Martin Savage, Andre Walker-Loud, William Detmold
2012-10-01T23:59:59.000Z
The low-energy n{Sigma}{sup -} interactions determine, in part, the role of the strange quark in dense matter, such as that found in astrophysical environments. The scattering phase-shifts for this system are determined from a numerical evaluation of the QCD path integral using the technique of Lattice QCD. Our results, performed at a pion mass of m{sub {pi}} ~ 389 MeV in two large lattice volumes, and at one lattice spacing, are extrapolated to the physical pion mass using effective field theory. The calculated interactions indicate that the strange quark plays an important role in dense matter.
Andreas Stathopoulos; Kostas Orginos
2008-06-12T23:59:59.000Z
We present a new algorithm that computes eigenvalues and eigenvectors of a Hermitian positive definite matrix while solving a linear system of equations with Conjugate Gradient (CG). Traditionally, all the CG iteration vectors could be saved and recombined through the eigenvectors of the tridiagonal projection matrix, which is equivalent theoretically to unrestarted Lanczos. Our algorithm capitalizes on the iteration vectors produced by CG to update only a small window of vectors that approximate the eigenvectors. While this window is restarted in a locally optimal way, the CG algorithm for the linear system is unaffected. Yet, in all our experiments, this small window converges to the required eigenvectors at a rate identical to unrestarted Lanczos. After the solution of the linear system, eigenvectors that have not accurately converged can be improved in an incremental fashion by solving additional linear systems. In this case, eigenvectors identified in earlier systems can be used to deflate, and thus accelerate, the convergence of subsequent systems. We have used this algorithm with excellent results in lattice QCD applications, where hundreds of right hand sides may be needed. Specifically, about 70 eigenvectors are obtained to full accuracy after solving 24 right hand sides. Deflating these from the large number of subsequent right hand sides removes the dreaded critical slowdown, where the conditioning of the matrix increases as the quark mass reaches a critical value. Our experiments show almost a constant number of iterations for our method, regardless of quark mass, and speedups of 8 over original CG for light quark masses.
Quantum chaos in QCD at finite temperature
H. Markum; R. Pullirsch; K. Rabitsch; T. Wettig
1997-09-24T23:59:59.000Z
We study complete eigenvalue spectra of the staggered Dirac matrix in quenched QCD on a $6^3\\times 4$ lattice. In particular, we investigate the nearest-neighbor spacing distribution $P(s)$ for various values of $\\beta$ both in the confinement and deconfinement phase. In both phases except far into the deconfinement region, the data agree with the Wigner surmise of random matrix theory which is indicative of quantum chaos. No signs of a transition to Poisson regularity are found, and the reasons for this result are discussed.
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.
Sekhar Chivukula
2010-01-08T23:59:59.000Z
The symmetries of a quantum field theory can be realized in a variety of ways. Symmetries can be realized explicitly, approximately, through spontaneous symmetry breaking or, via an anomaly, quantum effects can dynamically eliminate a symmetry of the theory that was present at the classical level. Quantum Chromodynamics (QCD), the modern theory of the strong interactions, exemplify each of these possibilities. The interplay of these effects determine the spectrum of particles that we observe and, ultimately, account for 99% of the mass of ordinary matter.
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.
Aspects of the Structure of the QCD Radiation Field
Reinhold Brueckner
2001-02-12T23:59:59.000Z
We consider the classical radiative solution to the QCD (quantum chromodynamics) dynamical equations and find trivial solutions similar to the electrodynamic situation when one considers singlet (colorless) radiation sources. We transpose the findings to quantum fields and identify radiation from hadron (meson) sources with gluon packages of 3 (2) gluons. Invoking the singlet character of the QCD matter and radiation field, we deduce that the blank (singlet) gluon packages are the elementary building blocks of QCD radiation, just as blank hadrons and mesons are the building blocks of baryon matter. Colorlessness of the gluon packages suggests a possibly simpler quasi-abelian behaviour, as far as linear superposition is involved, of the QCD singlet radiation field.
P. Nason; B. R. Webber; D. Ward; D. Lanske; L. A. del Pozo; F. Fabbri; B. Poli; G. Cowan; C. Padilla; M. Seymour; F. Hautmann; Yu. L. Dokshitzer; V. A. Khoze
1996-02-13T23:59:59.000Z
We discuss QCD studies that will be possible at LEP2. We examine both experimental and theoretical aspects of jets, fragmentation functions, multiplicities and particle spectra.
Improving the Dirac Operator in Lattice QCD
Christof Gattringer; C. B. Lang
2001-11-22T23:59:59.000Z
Recently various new concepts for the construction of Dirac operators in lattice Quantum Chromodynamics (QCD) have been introduced. These operators satisfy the so-called Ginsparg-Wilson condition (GWC), thus obeying the Atiyah-Singer index theorem and violating chiral symmetry only in a modest and local form. Here we present studies in 4-d for SU(3) gauge configurations with non-trivial topological content. We study the flow of eigenvalues and we compare the numerical stability and efficiency of a recently suggested chirally improved operator with that of others in this respect.
Dark matter, Mach's ether and the QCD vacuum
Cohen-Tannoudji, Gilles
2015-01-01T23:59:59.000Z
Here is proposed the idea of linking the dark matter issue, (considered as a major problem of contemporary research in physics) with two other open theoretical questions, one, almost centenary about the existence of an unavoidable ether in general relativity agreeing with the Mach's principle, and one more recent about the properties of the quantum vacuum of the quantum field theory of strong interactions, QuantumChromodynamics (QCD). According to this idea, on the one hand, dark matter and dark energy that, according to the current standard model of cosmology represent about 95% of the universe content, can be considered as two distinct forms of the Mach's ether, and, on the other hand, dark matter, as a perfect fluid emerging from the QCD vacuum could be modeled as a Bose Einstein condensate.
Nuclear reactions from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Briceno, Raul A. [JLAB; Davoudi, Zohreh; Luu, Thomas C.
2015-02-01T23:59:59.000Z
One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Nuclear Reactions from Lattice QCD
Raúl A. Briceño; Zohreh Davoudi; Thomas C. Luu
2014-11-25T23:59:59.000Z
One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Nuclear reactions from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
2015-02-01T23:59:59.000Z
One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some ofmore »the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less
Hadron Physics and QCD: Just the Basic Facts
Roberts, Craig D
2015-01-01T23:59:59.000Z
With discovery of the Higgs boson, the Standard Model of Particle Physics became complete. Its formulation is a remarkable story; and the process of verification is continuing, with the most important chapter being the least well understood. Quantum Chromodynamics (QCD) is that part of the Standard Model which is supposed to describe all of nuclear physics and yet, almost fifty years after the discovery of quarks, we are only just beginning to understand how QCD moulds the basic bricks for nuclei: pious, neutrons, protons. QCD is characterized by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB), whose implications are extraordinary. This contribution describes how DCSB, not the Higgs boson, generates more than 98% of the visible mass in the Universe, explains why confinement guarantees that condensates, those quantities that were commonly viewed as constant mass-scales that fill all spacetime, are instead wholly contained within hadrons, and elucidates a range of observable co...
Which Chiral Symmetry is Restored in High Temperature QCD?
Claude Bernard; Tom Blum; Carleton DeTar; Steven Gottlieb; Urs M. Heller; James E. Hetrick; K. Rummukainen; R. Sugar; D. Toussaint; Matthew Wingate
1996-11-27T23:59:59.000Z
Sigma models for the high temperature phase transition in quantum chromodynamics (QCD) suggest that at high temperature the SU(N_f) x SU(N_f) chiral symmetry becomes exact, but the anomalous axial U(1) symmetry need not be restored. In numerical lattice simulations, traditional methods for detecting symmetry restoration have sought multiplets in the screening mass spectrum. However, these methods were imprecise and the results, so far, incomplete. With improved statistics and methodology, we are now able to offer evidence for a restoration of the SU(2) x SU(2) chiral symmetry just above the crossover, but not of the axial U(1) chiral symmetry.
DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]
Huston, Joey [Co-Spokesperson; Ownes, Joseph [Co-Spokesperson
The Coordinated Theoretical-Experimental Project on QCD is a multi-institutional collaboration devoted to a broad program of research projects and cooperative enterprises in high-energy physics centered on Quantum Chromodynamics (QCD) and its implications in all areas of the Standard Model and beyond. The Collaboration consists of theorists and experimentalists at 18 universities and 5 national laboratories. More than 65 sets of Parton Distribution Functions are available for public access. Links to many online software tools, information about Parton Distribution Functions, papers, and other resources are also available.
Twenty-first Century Lattice Gauge Theory: Results from the QCD Lagrangian
Kronfeld, Andreas S.; /Fermilab
2012-03-01T23:59:59.000Z
Quantum chromodynamics (QCD) reduces the strong interactions, in all their variety, to an elegant nonabelian gauge theory. It clearly and elegantly explains hadrons at short distances, which has led to its universal acceptance. Since its advent, however, many of its long-distance, emergent properties have been believed to be true, without having been demonstrated to be true. This paper reviews a variety of results in this regime that have been established with lattice gauge theory, directly from the QCD Lagrangian. This body of work sheds light on the origin of hadron masses, its interplay with dynamical symmetry breaking, as well as on other intriguing features such as the phase structure of QCD. In addition, nonperturbative QCD is quantitatively important to many aspects of particle physics (especially the quark flavor sector), nuclear physics, and astrophysics. This review also surveys some of the most interesting connections to those subjects.
Hernández-Pinto, R J
2014-01-01T23:59:59.000Z
Quantum Chromodynamics is the most successful theory in particle physics. The understanding of all different signals at hadron colliders have been achieved due to the correct interpretation of the theory. In this paper we review some basic features of the theory of strong interactions and how it could be used in order to provide phenomenological distributions for the Large Hadron Collider. The main results presented in here can be found in Ref [1].
R. J. Hernández-Pinto
2014-10-24T23:59:59.000Z
Quantum Chromodynamics is the most successful theory in particle physics. The understanding of all different signals at hadron colliders have been achieved due to the correct interpretation of the theory. In this paper we review some basic features of the theory of strong interactions and how it could be used in order to provide phenomenological distributions for the Large Hadron Collider. The main results presented in here can be found in Ref [1].
Monte Carlo Methods in Quantum Field Theory
I. Montvay
2007-05-30T23:59:59.000Z
In these lecture notes some applications of Monte Carlo integration methods in Quantum Field Theory - in particular in Quantum Chromodynamics - are introduced and discussed.
QCD, Tevatron results and LHC prospects
Elvira, V.Daniel; /Fermilab
2008-08-01T23:59:59.000Z
We present a summary of the most recent measurements relevant to Quantum Chromodynamics (QCD) delivered by the D0 and CDF Tevatron experiments by May 2008. CDF and D0 are moving toward precision measurements of QCD based on data samples in excess of 1 fb-1. The inclusive jet cross sections have been extended to forward rapidity regions and measured with unprecedented precision following improvements in the jet energy calibration. Results on dijet mass distributions, bbbar dijet production using tracker based triggers, underlying event in dijet and Drell-Yan samples, inclusive photon and diphoton cross sections complete the list of measurements included in this paper. Good agreement with pQCD within errors is observed for jet production measurements. An improved and consistent theoretical description is needed for photon+jets processes. Collisions at the LHC are scheduled for early fall 2008, opening an era of discoveries at the new energy frontier, 5-7 times higher than that of the Tevatron.
Use of correlation matrices in lattice QCD
Lepzelter, David, 1981-
2004-01-01T23:59:59.000Z
This thesis explores the use of correlation matrices in analyzing Monte Carlo calculations from lattice quantum chromodynamics. Correlation matrices are a powerful tool for examining many problems in which significant ...
Hadron Physics and QCD: Just the Basic Facts
Craig D. Roberts
2015-02-01T23:59:59.000Z
With discovery of the Higgs boson, the Standard Model of Particle Physics became complete. Its formulation is a remarkable story; and the process of verification is continuing, with the most important chapter being the least well understood. Quantum Chromodynamics (QCD) is that part of the Standard Model which is supposed to describe all of nuclear physics and yet, almost fifty years after the discovery of quarks, we are only just beginning to understand how QCD moulds the basic bricks for nuclei: pious, neutrons, protons. QCD is characterized by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB), whose implications are extraordinary. This contribution describes how DCSB, not the Higgs boson, generates more than 98% of the visible mass in the Universe, explains why confinement guarantees that condensates, those quantities that were commonly viewed as constant mass-scales that fill all spacetime, are instead wholly contained within hadrons, and elucidates a range of observable consequences of confinement and DCSB whose measurement is the focus of a vast international experimental programme.
Formal Developments for Lattice QCD with Applications to Hadronic Systems
Zohreh Davoudi
2014-09-05T23:59:59.000Z
Lattice quantum chromodynamics (QCD) will soon become the primary theoretical tool in rigorous studies of single- and multi-hadron sectors of QCD. It is truly ab initio meaning that its only parameters are those of standard model. The result of a lattice QCD calculation corresponds to that of nature only in the limit when the volume of spacetime is taken to infinity and the spacing between discretized points on the lattice is taken to zero. A better understanding of these discretization and volume effects not only provides the connection to the infinite-volume continuum observables, but also leads to optimized calculations that can be performed with available computational resources. This thesis includes various formal developments in this direction, along with proposals for improvements, to be applied to the upcoming lattice QCD studies of nuclear and hadronic systems. Among these developments are i) an analytical investigation of the recovery of rotational symmetry with the use of suitably-formed smeared operators toward the continuum limit, ii) an extension of the Luscher finite-volume method to two-nucleon systems with arbitrary angular momentum, spin, parity and center of mass momentum, iii) the application of such formalism in extracting the scattering parameters of the 3S1-3D1 coupled channels, iv) an investigation of twisted boundary conditions in the single- and two-hadron sectors, with proposals for improving the volume-dependence of the deuteron binding energy upon proper choices of boundary conditions, and v) exploring the volume dependence of the masses of hadrons and light-nuclei due to quantum electrodynamic interactions, including the effects arising from particles' compositeness. The required background as well as a brief status report of the field pertinent to the discussions in this thesis are presented.
Transversity from First Principles in QCD
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
2012-02-16T23:59:59.000Z
Transversity observables, such as the T-odd Sivers single-spin asymmetry measured in deep inelastic lepton scattering on polarized protons and the distributions which are measured in deeply virtual Compton scattering, provide important constraints on the fundamental quark and gluon structure of the proton. In this talk I discuss the challenge of computing these observables from first principles; i.e.; quantum chromodynamics, itself. A key step is the determination of the frame-independent light-front wavefunctions (LFWFs) of hadrons - the QCD eigensolutions which are analogs of the Schroedinger wavefunctions of atomic physics. The lensing effects of initial-state and final-state interactions, acting on LFWFs with different orbital angular momentum, lead to T-odd transversity observables such as the Sivers, Collins, and Boer-Mulders distributions. The lensing effect also leads to leading-twist phenomena which break leading-twist factorization such as the breakdown of the Lam-Tung relation in Drell-Yan reactions. A similar rescattering mechanism also leads to diffractive deep inelastic scattering, as well as nuclear shadowing and non-universal antishadowing. It is thus important to distinguish 'static' structure functions, the probability distributions computed the target hadron's light-front wavefunctions, versus 'dynamical' structure functions which include the effects of initial- and final-state rescattering. I also discuss related effects such as the J = 0 fixed pole contribution which appears in the real part of the virtual Compton amplitude. AdS/QCD, together with 'Light-Front Holography', provides a simple Lorentz-invariant color-confining approximation to QCD which is successful in accounting for light-quark meson and baryon spectroscopy as well as hadronic LFWFs.
Seth, K K
1989-01-01T23:59:59.000Z
This report discusses experiments dealing with: quantum chromodynamics; nuclear physics with QCD overtones; and nuclear structure. (LSP).
Lattice QCD ensembles with four flavors of highly improved staggered quarks
The MILC Collaboration; A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Komijani; J. Laiho; L. Levkova; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water; Ran Zhou
2013-05-16T23:59:59.000Z
We present results from our simulations of quantum chromodynamics (QCD) with four flavors of quarks: u, d, s, and c. These simulations are performed with a one-loop Symanzik improved gauge action, and the highly improved staggered quark (HISQ) action. We are generating gauge configurations with four values of the lattice spacing ranging from 0.06 fm to 0.15 fm, and three values of the light quark mass, including the value for which the Goldstone pion mass is equal to the physical pion mass. We discuss simulation algorithms, scale setting, taste symmetry breaking, and the autocorrelations of various quantities. We also present results for the topological susceptibility which demonstrate the improvement of the HISQ configurations relative to those generated earlier with the asqtad improved staggered action.
Nuclear Forces from Lattice Quantum Chromodynamics Martin J. Savage
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ANL/ALCF/ESP-13/11 Lattice Quantum Chromodynamics
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5 QPX in QLA We added a few QPX routines using XLC intrinsics in QLA. QLA is a linear algebra library in the USQCD SciDAC modules 2. One of most important calculations in...
Lattice Quantum Chromodynamics Project and SCience Gateway at NERSC
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Nuclear Forces from Lattice Quantum Chromodynamics Martin J....
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500 K cores, wallclock limited, as many as needed * IO will be integrated database(s), SQL, hdf5 Monday, April 28, 2014 Compute (3) * Chroma exploits GPU * development is ongoing...
Lattice Quantum Chromodynamics (SPI, mapping, site ordering, and QPX in
Office of Scientific and Technical Information (OSTI)
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Contemporary continuum QCD approaches to excited hadrons
Bruno El-Bennich; Eduardo Rojas
2015-09-09T23:59:59.000Z
Amongst the bound states produced by the strong interaction, radially excited meson and nucleon states offer an important phenomenological window into the long-range behavior of the coupling constant in Quantum Chromodynamics. We here report on some technical details related to the computation of the bound state's eigenvalue spectrum in the framework of Bethe-Salpeter and Faddeev equations.
Henner, V K; Belozerova, T S
2015-01-01T23:59:59.000Z
The first part of our analysis uses the wavelet method to compare the Quantum Chromodynamic (QCD) prediction for the ratio of hadronic to muon cross sections in electron-positron collisions, $R$, with experimental data for $R$ over a center of mass energy range up to 7.5 GeV. A direct comparison of the raw experimental data and the QCD prediction is difficult because the data have a wide range of structures and large statistical errors and the QCD description contains sharp quark-antiquark thresholds. However, a meaningful comparison can be made if a type of "smearing" procedure is used to smooth out rapid variations in both the theoretical and experimental values of $R$. A wavelet analysis (WA) can be used to achieve this smearing effect. In the second part of the analysis we concentrate on the 3.0 - 6.0 GeV energy region containing the relatively wide charmonium resonances $\\psi(1^-)$. We use the wavelet methodology to distinguish these resonances from experimental noise, background and from each other, and...
V. K. Henner; C. L. Davis; T. S. Belozerova
2015-06-12T23:59:59.000Z
The first part of our analysis uses the wavelet method to compare the Quantum Chromodynamic (QCD) prediction for the ratio of hadronic to muon cross sections in electron-positron collisions, $R$, with experimental data for $R$ over a center of mass energy range up to 7.5 GeV. A direct comparison of the raw experimental data and the QCD prediction is difficult because the data have a wide range of structures and large statistical errors and the QCD description contains sharp quark-antiquark thresholds. However, a meaningful comparison can be made if a type of "smearing" procedure is used to smooth out rapid variations in both the theoretical and experimental values of $R$. A wavelet analysis (WA) can be used to achieve this smearing effect. In the second part of the analysis we concentrate on the 3.0 - 6.0 GeV energy region containing the relatively wide charmonium resonances $\\psi(1^-)$. We use the wavelet methodology to distinguish these resonances from experimental noise, background and from each other, and are thus able to determine more reliably the parameters of these states. These two analyses are examples of the usefulness of WA in extracting information in a model independent way from high energy physics data.
T. Alho; M. Jarvinen; K. Kajantie; E. Kiritsis; K. Tuominen
2015-03-26T23:59:59.000Z
We consider the finite temperature phase diagram of holographic QCD in the Veneziano limit (Nc large, Nf large with xf=Nf/Nc fixed) and calculate one string-loop corrections to the free energy in certain approximations. Such corrections, especially due to the pion modes are unsuppressed in the Veneziano limit. We find that under some extra assumptions the first order transition following from classical gravity solutions can become second order. If stringy asymptotics are of a special form and there are residual interactions it may even become of third order. Operationally these computations imply modelling the low temperature chiral symmetry breaking phase with a hadron gas containing Nf^2 massless Goldstone bosons and an exponential spectrum of massive hadrons. A third order transition is possible only if repulsive hadron interactions via the excluded volume effect are included.
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
2011-08-12T23:59:59.000Z
I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spin asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the square of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of searches for new physics at the LHC. Other novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates.
Karsch,F.; Kharzeev, D.; Molnar, K.; Petreczky, P.; Teaney, D.
2008-04-21T23:59:59.000Z
The interpretation of relativistic heavy-ion collisions at RHIC energies with thermal concepts is largely based on the relative success of ideal (nondissipative) hydrodynamics. This approach can describe basic observables at RHIC, such as particle spectra and momentum anisotropies, fairly well. On the other hand, recent theoretical efforts indicate that dissipation can play a significant role. Ideally viscous hydrodynamic simulations would extract, if not only the equation of state, but also transport coefficients from RHIC data. There has been a lot of progress with solving relativistic viscous hydrodynamics. There are already large uncertainties in ideal hydrodynamics calculations, e.g., uncertainties associated with initial conditions, freezeout, and the simplified equations of state typically utilized. One of the most sensitive observables to the equation of state is the baryon momentum anisotropy, which is also affected by freezeout assumptions. Up-to-date results from lattice quantum chromodynamics on the transition temperature and equation of state with realistic quark masses are currently available. However, these have not yet been incorporated into the hydrodynamic calculations. Therefore, the RBRC workshop 'Hydrodynamics in Heavy Ion Collisions and QCD Equation of State' aimed at getting a better understanding of the theoretical frameworks for dissipation and near-equilibrium dynamics in heavy-ion collisions. The topics discussed during the workshop included techniques to solve the dynamical equations and examine the role of initial conditions and decoupling, as well as the role of the equation of state and transport coefficients in current simulations.
Robi Peschanski
2006-10-02T23:59:59.000Z
When quarks and gluons are led to form a dense medium, like in high energy or/and heavy-ion collisions, it is interesting to ask the question which are the relevant degrees of freedom that Quantum Chromodynamics predict. The present notes correspond to two lectures given at Zakopane in the (rainy) summer of 2006, where this question is adressed concretely in two cases, one in the regime of weak coupling, the other one at strong coupling. Each case corresponds to the study of a dynamically important transient phase of quarks and gluons expected to appear from Quantum Chromodynamics. In lecture I, we examine the dynamical phase space of gluon transverse momenta near the so-called ``saturation'' phase including its fluctuation pattern. In lecture II, we study the dynamics of strongly interacting gauge-theory matter (modelling quark-gluon plasma) using the AdS/CFT duality between gauge field theory at strong coupling and a gravitational background in Anti-de Sitter space.
QCD Phase Transitions, Volume 15
Schaefer, T.; Shuryak, E.
1999-03-20T23:59:59.000Z
The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.
Thomas Gehrmann
2010-07-28T23:59:59.000Z
In this talk, I review recent developments in perturbative QCD and their applications to collider physics.
Z. Fodor
2007-11-02T23:59:59.000Z
Recent results on QCD thermodynamics are presented. The nature of the T>0 transition is determined, which turns out to be an analytic cross-over. The absolute scale for this transition is calculated. The temperature dependent static potential is given. The results were obtained by using a Symanzik improved gauge and stout-link improved fermionic action. In order to approach the continuum limit four different sets of lattice spacings were used with temporal extensions N_t=4, 6, 8 and 10 (they correspond to lattice spacings a \\sim 0.3, 0.2, 0.15 and 0.12 fm). A new technique is presented, which --in contrast to earlier methods-- enables one to determine the equation of state at very large temperatures.
Murray Gell-Mann, the Eightfold Way, Quarks, and Quantum Chromodynamics
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QCDOC -Quantum Chromodynamics on a Chip at BNL | U.S. DOE Office of Science
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Light Nuclei and HyperNuclei from Quantum Chromodynamics in the Limit of
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Book Review: Tian Yu Cao, From Current Algebra to Quantum Chromodynamics: A Case
Wüthrich, Christian
the best theory of the strong nuclear force and the hadrons it governs, such as the protons and neutrons, a diffractive production process, incoherent scattering, a deep inelastic scattering process, the gauge
The hadron spectrum from lattice QCD
Peardon, Mike [School of Mathematics, Trinity College Dublin (Ireland)
2010-08-05T23:59:59.000Z
Lattice spectroscopy is becoming increasingly sophisticated. This review will introduce the methodology and describe progress made recently probing the spectrum of excitations of QCD. The focus will be on describing new developments that enable excited states, exotic quantum numbers and resonances to be explored.
Ruck, H.M.
2010-01-01T23:59:59.000Z
Energy under Contract W-7405-ENG-48. REFERENCES: H.M. Ruck,under Contract W-7405-ENG-48 POLYNOMIAL CHROMODYNAMICSof Energy under Contract W-7405-ENG-48. 2. STRUCTURE OF
Matching NLO QCD computations and parton shower simulations.
Frixione, Stefano; Webber, Bryan R
Research Council and by the EU Fourth Framework Programme ‘Training and Mobility of Researchers’, Network ‘Quantum Chromodynamics and the Deep Structure of Elementary Particles’, contract FMRX-CT98-0194 (DG 12 - MIHT). †On leave of absence from INFN, Sez... suggests the following procedure: • Pick at random 0 ? x ? 1. • Generate an MC event with xM(x) as maximum energy available to the photon in the first branching; attach to this event the weight wEV = aR(x)/x. 9 • Generate another MC event (a “counter...
Dense QCD: Overhauser or BCS pairing?
Park, Byung-Yoon [School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea (Korea, Republic of) [School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea (Korea, Republic of); Department of Physics, Chungnam National University, Taejon 305-764, Korea (Korea, Republic of); Rho, Mannque [School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea (Korea, Republic of) [School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea (Korea, Republic of); Service de Physique Theorique, CE Saclay, 91191 Gif-sur-Yvette, (France); Wirzba, Andreas [Department of Physics and Astronomy, SUNY-Stony Brook, New York 11794 (United States) [Department of Physics and Astronomy, SUNY-Stony Brook, New York 11794 (United States); FZ Juelich, Institut fuer Kernphysik (Theorie), D-52425 Juelich, (Germany); Zahed, Ismail [School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea (Korea, Republic of) [School of Physics, Korea Institute for Advanced Study, Seoul 130-012, Korea (Korea, Republic of); Department of Physics and Astronomy, SUNY-Stony Brook, New York 11794 (United States)
2000-08-01T23:59:59.000Z
We discuss the Overhauser effect (particle-hole pairing) versus the BCS effect (particle-particle or hole-hole pairing) in QCD at large quark density. In weak coupling and to leading logarithm accuracy, the pairing energies can be estimated exactly. For a small number of colors, the BCS effect overtakes the Overhauser effect, while for a large number of colors the opposite takes place, in agreement with a recent renormalization group argument. In strong coupling with large pairing energies, the Overhauser effect may be dominant for any number of colors, suggesting that QCD may crystallize into an insulator at a few times nuclear matter density, a situation reminiscent of dense Skyrmions. The Overhauser effect is dominant in QCD in 1+1 dimensions, although susceptible to quantum effects. It is sensitive to temperature in all dimensions. (c) 2000 The American Physical Society.
QCD Evolution Workshop: Introduction
Alexei Prokudin
2012-10-15T23:59:59.000Z
The introduction talk given at the beginning of QCD Evolution workshop held in Thomas Jefferson National Accelerator Facility (Jefferson Lab) on May 14 -17, 2012.
U. van Kolck
2008-12-20T23:59:59.000Z
Effective field theories provide a bridge between QCD and nuclear physics. I discuss light nuclei from this perspective, emphasizing the role of fine-tuning.
B R Webber
1994-10-12T23:59:59.000Z
The current status of the QCD coupling constant $\\alpha_S$ and experimental and theoretical studies of hadronic jets are reviewed.
QCD PHASE TRANSITIONS-VOLUME 15.
SCHAFER,T.
1998-11-04T23:59:59.000Z
The title of the workshop, ''The QCD Phase Transitions'', in fact happened to be too narrow for its real contents. It would be more accurate to say that it was devoted to different phases of QCD and QCD-related gauge theories, with strong emphasis on discussion of the underlying non-perturbative mechanisms which manifest themselves as all those phases. Before we go to specifics, let us emphasize one important aspect of the present status of non-perturbative Quantum Field Theory in general. It remains true that its studies do not get attention proportional to the intellectual challenge they deserve, and that the theorists working on it remain very fragmented. The efforts to create Theory of Everything including Quantum Gravity have attracted the lion share of attention and young talent. Nevertheless, in the last few years there was also a tremendous progress and even some shift of attention toward emphasis on the unity of non-perturbative phenomena. For example, we have seen some. efforts to connect the lessons from recent progress in Supersymmetric theories with that in QCD, as derived from phenomenology and lattice. Another example is Maldacena conjecture and related development, which connect three things together, string theory, super-gravity and the (N=4) supersymmetric gauge theory. Although the progress mentioned is remarkable by itself, if we would listen to each other more we may have chance to strengthen the field and reach better understanding of the spectacular non-perturbative physics.
Jefferson Lab - QCD Evolution 2015
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
functions, and the associated progress in perturbative QCD, lattice QCD and effective field theory techniques we look forward with great enthusiasm to the 2015 meeting. We will...
Weyl symmetric structure of QCD vacuum
Y. M. Cho; D. G. Pak; P. M. Zhang; L. P. Zou
2012-09-12T23:59:59.000Z
We consider Weyl symmetric structure of the classical vacuum in quantum chromodynamics. In the framework of formalism of gauge invariant Abelian projection we show that classical vacuums can be constructed in terms of Killing vector fields on the group SU(3). Consequently, homotopic classes of Killing vector fields determine the topological structure of the vacuum. In particular, the second homotopy group \\pi_2(SU(3)/U(1)\\times U(1)) describes all topologically non-equivalent vacuums which are classified by two topological numbers. For each given Killing vector field one can construct six vacuums forming Weyl sextet representation. An interesting feature of SU(3) gauge theory is that it admits a Weyl symmetric vacuum represented by a linear superposition of the six vacuums from the Weyl vacuum sextet. A non-trivial manifestation of Weyl symmetry is demonstrated on monopole solutions. We construct a family of finite energy monopole solutions in Yang-Mills-Higgs theory which includes Weyl monopole sextet. From the analysis of the classical vacuum structure and monopole solutions we conjecture that a similar Weyl symmetric vacuum structure can be realized in quantum theory.
Inhomogeneous color superconductivity and the cooling of compact stars
M. Ruggieri
2007-04-13T23:59:59.000Z
In this talk I discuss the inhomogeneous (LOFF) color superconductive phases of Quantum Chromodynamics (QCD). In particular, I show the effect of a core of LOFF phase on the cooling of a compact star.
Forward Di-hadron Asymmetries from p + p at ?s = 200 GeV at STAR
Drachenberg, James Lucas
2012-07-16T23:59:59.000Z
One unresolved question in hadronic physics is the origin of large transverse single-spin asymmetries, AN, observed in hadron production from high-energy polarized-proton collisions. Collinear perturbative Quantum Chromodynamics (pQCD) predicts...
Jet quenching in heavy-ion collisions at LHC with CMS detector
Yilmaz, Yetkin
2013-01-01T23:59:59.000Z
The collision of highly relativistic nuclei can produce a volume of high energy density which can be used to learn about the behavior of quantum chromodynamics (QCD) at extreme conditions, such as those of the universe at ...
I. G. Knowles; T. Sjostrand; A. Blondel; A. Boehrer; C. D. Buchanan; D. G. Charlton; S. -L. Chu; S. Chun; G. Dissertori; D. Duchesneau; J. W. Gary; M. Gibbs; A. Grefrath; G. Gustafson; J. Hakkinen; K. Hamacher; K. Kato; L. Lonnblad; W. Metzger; R. Moller; T. Munehisa; R. Odorico; Y. Pei; G. Rudolph; S. Sarkar; M. H. Seymour; J. C. Thompson; S. Todorova; B. R. Webber
1996-01-04T23:59:59.000Z
This report is a survey on QCD Event Generator issues of relevance for LEP 2. It contains four main sections: a summary of experience from LEP 1, extrapolations to LEP 2 energies, Monte Carlo descriptions and standardization issues.
Exact Amplitude--Based Resummation QCD Predictions and LHC Data
Ward, B F L; Yost, S A
2014-01-01T23:59:59.000Z
We present the current status of the comparisons with the respective data of the predictions of our approach of exact amplitude-based resummation in quantum field theory as applied to precision QCD calculations as needed for LHC physics, using the MC Herwiri1.031. The agreement between the theoretical predictions and the data exhibited continues to be encouraging.
Matching Hagedorn mass spectrum with Lattice QCD
Lo, Pok Man; Redlich, Krzysztof; Sasaki, Chihiro
2015-01-01T23:59:59.000Z
Based on recent Lattice QCD (LQCD) results obtained at finite temperature, we discuss modeling of the hadronic phase of QCD in the framework of Hadron Resonance Gas (HRG) with discrete and continuous mass spectra. We focus on fluctuations of conserved charges, and show how a common limiting temperature can be used to constrain the Hagedorn exponential mass spectrum in different sectors of quantum number, through a matching of HRG and LQCD. For strange baryons, the extracted spectra are found to be consistent with all known and expected states listed by the Particle Data Group (PDG). The strange-mesonic sector, however, requires additional states in the intermediate mass range beyond that embodied in the database.
Matching Hagedorn mass spectrum with Lattice QCD
Pok Man Lo; Micha? Marczenko; Krzysztof Redlich; Chihiro Sasaki
2015-07-23T23:59:59.000Z
Based on recent Lattice QCD (LQCD) results obtained at finite temperature, we discuss modeling of the hadronic phase of QCD in the framework of Hadron Resonance Gas (HRG) with discrete and continuous mass spectra. We focus on fluctuations of conserved charges, and show how a common limiting temperature can be used to constrain the Hagedorn exponential mass spectrum in different sectors of quantum number, through a matching of HRG and LQCD. For strange baryons, the extracted spectra are found to be consistent with all known and expected states listed by the Particle Data Group (PDG). The strange-mesonic sector, however, requires additional states in the intermediate mass range beyond that embodied in the database.
Multigrid Preconditioning for the Overlap Operator in Lattice QCD
James Brannick; Andreas Frommer; Karsten Kahl; Björn Leder; Matthias Rottmann; Artur Strebel
2014-10-27T23:59:59.000Z
The overlap operator is a lattice discretization of the Dirac operator of quantum chromodynamics, the fundamental physical theory of the strong interaction between the quarks. As opposed to other discretizations it preserves the important physical property of chiral symmetry, at the expense of requiring much more effort when solving systems with this operator. We present a preconditioning technique based on another lattice discretization, the Wilson-Dirac operator. The mathematical analysis precisely describes the effect of this preconditioning in the case that the Wilson-Dirac operator is normal. Although this is not exactly the case in realistic settings, we show that current smearing techniques indeed drive the Wilson-Dirac operator towards normality, thus providing a motivation why our preconditioner works well in computational practice. Results of numerical experiments in physically relevant settings show that our preconditioning yields accelerations of up to one order of magnitude.
Fourier analysis of the flux-tube distribution in SU(3) lattice QCD
Arata Yamamoto
2010-04-16T23:59:59.000Z
This letter presents a novel analysis of the action/energy density distribution around a static quark-antiquark pair in SU(3) lattice quantum chromodynamics. Using the Fourier transformation of the link variable, we remove the high-momentum gluon and extract the flux-tube component from the action/energy density. When the high-momentum gluon is removed, the statistical fluctuation is drastically suppressed, and the singularities from the quark self-energy disappear. The obtained flux-tube component is broadly distributed around the line connecting the quark and the antiquark.
Determination of alpha_s from the QCD static energy: an update
Alexei Bazavov; Nora Brambilla; Xavier Garcia i Tormo; Peter Petreczky; Joan Soto; Antonio Vairo
2014-11-04T23:59:59.000Z
We present an update of our determination of the strong coupling alpha_s from the quantum chromodynamics static energy. This updated analysis includes new lattice data, at smaller lattice spacings and reaching shorter distances, the use of better suited perturbative expressions to compare with data in a wider distance range, and a comprehensive and detailed estimate of the error sources that contribute to the uncertainty of the final result. Our updated value for alpha_s at the Z-mass scale, M_Z, is alpha_s(M_Z)=0.1166^{+0.0012}_{-0.0008}, which supersedes our previous result.
Renormalization of Hamiltonian QCD
A. Andrasi; J. C. Taylor
2007-04-11T23:59:59.000Z
We study to one-loop order the renormalization of QCD in the Coulomb gauge using the Hamitonian formalism. Divergences occur which might require counter-terms outside the Hamiltonian formalism, but they can be cancelled by a redefinition of the Yang-Mills electric field.
Feryal Ozel; Dimitrios Psaltis; Scott Ransom; Paul Demorest; Mark Alford
2010-10-27T23:59:59.000Z
The recent measurement of the Shapiro delay in the radio pulsar PSR J1614-2230 yielded a mass of 1.97 +/- 0.04 M_sun, making it the most massive pulsar known to date. Its mass is high enough that, even without an accompanying measurement of the stellar radius, it has a strong impact on our understanding of nuclear matter, gamma-ray bursts, and the generation of gravitational waves from coalescing neutron stars. This single high mass value indicates that a transition to quark matter in neutron-star cores can occur at densities comparable to the nuclear saturation density only if the quarks are strongly interacting and are color superconducting. We further show that a high maximum neutron-star mass is required if short duration gamma-ray bursts are powered by coalescing neutron stars and, therefore, this mechanism becomes viable in the light of the recent measurement. Finally, we argue that the low-frequency (<= 500 Hz) gravitational waves emitted during the final stages of neutron-star coalescence encode the properties of the equation of state because neutron stars consistent with this measurement cannot be centrally condensed. This will facilitate the measurement of the neutron star equation of state with Advanced LIGO/Virgo.
Wesley Smith, U. Wisconsin, January 11, 2007 Aspen Winter Conference: Experimental QCD - 1 QCD results from collidersQCD results from collidersQCD results from colliders 2007 Aspen Winter Conference This talk is available on: http://www.hep.wisc.edu/wsmith/files/exp_qcd_smith_aspen07.pdf #12;Wesley Smith
Infrared freezing of Euclidean observables and analyticity in perturbative QCD
Irinel Caprini; Jan Fischer
2006-12-21T23:59:59.000Z
The renormalization-group improved finite order expansions of the QCD observables have an unphysical singularity in the Euclidean region, due to the Landau pole of the running coupling. Recently it was claimed that, by using a modified Borel representation, the leading one-chain term in a skeleton expansion of the Euclidean QCD observables is finite and continuous across the Landau pole, and then exhibits an infrared freezing behaviour, vanishing at $Q^2=0$. In the present paper we show, using for illustration the Adler-${\\cal D}$ function, that the above Borel prescription violates the causality properties expressed by energy-plane analyticity: the function ${\\cal D}(Q^2)$ thus defined is the boundary value of a piecewise analytic function in the complex plane, instead of being a standard analytic function. So, the price to be paid for the infrared freezing of Euclidean QCD observables is the loss of a fundamental property of local quantum field theory.
Gupta, R.
1998-12-31T23:59:59.000Z
The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.
Bjorken, J.D.
1996-10-01T23:59:59.000Z
New directions for exploring QCD at future high-energy colliders are sketched. These include jets within jets. BFKL dynamics, soft and hard diffraction, searches for disoriented chiral condensate, and doing a better job on minimum bias physics. The new experimental opportunities include electron-ion collisions at HERA, a new collider detector at the C0 region of the TeVatron, and the FELIX initiative at the LHC.
Bryan R. Webber
2010-09-29T23:59:59.000Z
I discuss the calculation of QCD jet rates in e+e- annihilation as a testing ground for parton shower simulations and jet finding algorithms.
Lattice QCD calculations for nuclear physics
Parreño, A. [Dept. d'Estructura i Constituents de la Matèria. Institut de Ciències del Cosmos (ICC), Universitat de Barcelona, Martí i Franquès 1, E08028 (Spain)
2014-07-23T23:59:59.000Z
I present some recent results regarding the use of numerical Lattice QCD techniques to describe light nuclear systems from the underlying theory of the strong interaction, QCD.
QCD coupling constants and VDM
Erkol, G.; Ozpineci, A.; Zamiralov, V. S. [Laboratory for Fundamental Research, Ozyegin University, Istanbul (Turkey); Physics Department, Middle East Technical University, 06531, Ankara (Turkey); Skobeltsyn Institute of Nuclear Physics, Lomonosov MSU, Moscow (Russian Federation)
2012-10-23T23:59:59.000Z
QCD sum rules for coupling constants of vector mesons with baryons are constructed. The corresponding QCD sum rules for electric charges and magnetic moments are also derived and with the use of vector-meson-dominance model related to the coupling constants. The VDM role as the criterium of reciprocal validity of the sum rules is considered.
Equilibrium Thermodynamics of Lattice QCD
D. K. Sinclair
2007-02-03T23:59:59.000Z
Lattice QCD allows us to simulate QCD at non-zero temperature and/or densities. Such equilibrium thermodynamics calculations are relevant to the physics of relativistic heavy-ion collisions. I give a brief review of the field with emphasis on our work.
Feng Wu
2010-04-13T23:59:59.000Z
Based on the uniqueness and universality of gravity, it is clear that theories with different dynamical exponents are related in the holographic approach. Concretely, we construct an M-theory background from pure QCD dual and show that a deformed $Sch_{6}^{4}$ geometry is obtained by compactification from the same background. The deformed $Sch_{6}^{4}$ geometry is considered as the geometrical realization of a four-dimensional nonrelativistic field theory. Several aspects of this nonrelativistic field theory are studied in the holographic picture.
John B. Kogut
2002-08-30T23:59:59.000Z
I review present challenges that QCD in extreme environments presents to lattice gauge theory. Recent data and impressions from RHIC are emphasized. Physical pictures of heavy ion wavefunctions, collisions and the generation of the Quark Gluon Plasma are discussed, with an eye toward engaging the lattice and its numerical methods in more interaction with the experimental and phenomenological developments. Controversial, but stimulating scenarios which can be confirmed or dismissed by lattice methods are covered. In the second half of the talk, several promising developments presented at the conference Lattice 2002 are reviewed.
None
2011-10-06T23:59:59.000Z
Modern QCD - Lecture 1 Starting from the QCD Lagrangian we will revisit some basic QCD concepts and derive fundamental properties like gauge invariance and isospin symmetry and will discuss the Feynman rules of the theory. We will then focus on the gauge group of QCD and derive the Casimirs CF and CA and some useful color identities.
Rethinking the QCD collisional energy loss
A. Peshier
2006-07-25T23:59:59.000Z
It is shown that to leading order the collisional energy loss of an energetic parton in the hot quark gluon plasma reads $dE/dx \\sim \\alpha(m_D^2)T^2$, where the scale of the coupling is determined by the (parametrically soft) Debye screening mass. Compared to previous expressions derived by Bjorken and other authors, $dE^B/dx \\sim \\alpha^2 T^2 \\ln(ET/m_D^2)$, the rectified result takes into account the running of the coupling, as dictated by quantum corrections beyond tree level. As one significant consequence, due to asymptotic freedom, the QCD collisional energy loss becomes independent of the jet energy in the limit $E \\gg T$. It is advocated that this resummation improved perturbative result might be useful to (re-)estimate the collisional energy loss for temperatures relevant in heavy ion phenomenology.
Spin and Resonant States in QCD
Kirchbach, M
2003-01-01T23:59:59.000Z
I make the case that the nucleon excitations do not exist as isolated higher spin states but are fully absorbed by (K/2,K/2)x [(1/2,0)+(0,1/2)] multiplets taking their origin from the rotational and vibrational excitations of an underlying quark--diquark string. The Delta(1232) spectrum presents itself as the exact replica (up to Delta (1600)) of the nucleon spectrum with the K- clusters being shifted upward by about 200 MeV. QCD inspired arguments support legitimacy of the quark-diquark string. The above K multiplets can be mapped (up to form-factors) onto Lorentz group representation spaces of the type \\psi_{\\mu_1...\\mu_K}, thus guaranteeing covariant description of resonant states. The quantum \\psi_{\\mu_1...\\mu_K} states are of multiple spins at rest, and of undetermined spins elsewhere.
Stanley J. Brodsky; Abhay L. Deshpande; Haiyan Gao; Robert D. McKeown; Curtis A. Meyer; Zein-Eddine Meziani; Richard G. Milner; Jianwei Qiu; David G. Richards; Craig D. Roberts
2015-02-19T23:59:59.000Z
This document presents the recommendations and scientific conclusions from the Town Meeting on QCD and Hadronic Physics that took place in the period 13-15 September 2014 at Temple University as part of the NSAC 2014 Long Range Planning process. It highlights progress in hadron physics in the seven years since the 2007 Long Range Plan (LRP07), and presents a vision for the future by identifying key questions and plausible paths to solutions which should define our next decade. In defining the priority of outstanding physics opportunities for the future, both prospects for the short (roughly 5 years) and longer term (beyond 10 years) are identified together with the facilities, personnel and other resources needed to maximize the discovery potential in hadronic physics worldwide. In this connection, the potential of an electron ion collider is highlighted.
Excited Baryons in Holographic QCD
de Teramond, Guy F.; /Costa Rica U.; Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins
2011-11-08T23:59:59.000Z
The light-front holographic QCD approach is used to describe baryon spectroscopy and the systematics of nucleon transition form factors. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. The transition from the hard-scattering perturbative domain to the non-perturbative region is sensitive to the detailed dynamics of confined quarks and gluons. Computations of such phenomena from first principles in QCD are clearly very challenging. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time; however, dynamical observables in Minkowski space-time, such as the time-like hadronic form factors are not amenable to Euclidean numerical lattice computations.
Chiral dynamics in the low-temperature phase of QCD
Bastian B. Brandt; Anthony Francis; Harvey B. Meyer; Daniel Robaina
2014-06-21T23:59:59.000Z
We investigate the low-temperature phase of QCD and the crossover region with two light flavors of quarks. The chiral expansion around the point $(T,m=0)$ in the temperature vs. quark-mass plane indicates that a sharp real-time excitation exists with the quantum numbers of the pion. An exact sum rule is derived for the thermal modification of the spectral function associated with the axial charge density; the (dominant) pion pole contribution obeys the sum rule. We determine the two parameters of the pion dispersion relation using lattice QCD simulations and test the applicability of the chiral expansion. The time-dependent correlators are also analyzed using the Maximum Entropy Method, yielding consistent results. Finally, we test the predictions of the chiral expansion around the point $(T=0,m=0)$ for the temperature dependence of static observables.
Cheng, M.; Christ, N. H.; Mawhinney, R. D. [Physics Department, Columbia University, New York, New York 10027 (United States); Datta, S.; Jung, C.; Schmidt, C.; Umeda, T. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Heide, J. van der; Kaczmarek, O.; Laermann, E.; Miao, C. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Karsch, F. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Petreczky, P. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973 (United States); Petrov, K. [Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)
2006-09-01T23:59:59.000Z
We present a detailed calculation of the transition temperature in QCD with two light and one heavier (strange) quark mass on lattices with temporal extent N{sub {tau}}=4 and 6. Calculations with improved staggered fermions have been performed for various light to strange quark mass ratios in the range, 0.05{<=}m-circumflex{sub l}/m-circumflex{sub s}{<=}0.5, and with a strange quark mass fixed close to its physical value. From a combined extrapolation to the chiral (m-circumflex{sub l}{yields}0) and continuum (aT{identical_to}1/N{sub {tau}}{yields}0) limits we find for the transition temperature at the physical point T{sub c}r{sub 0}=0.457(7) where the scale is set by the Sommer-scale parameter r{sub 0} defined as the distance in the static quark potential at which the slope takes on the value (dV{sub qq}(r)/dr){sub r=r{sub 0}}=1.65/r{sub 0}{sup 2}. Using the currently best known value for r{sub 0} this translates to a transition temperature T{sub c}=192(7)(4) MeV. The transition temperature in the chiral limit is about 3% smaller. We discuss current ambiguities in the determination of T{sub c} in physical units and also comment on the universal scaling behavior of thermodynamic quantities in the chiral limit.
anQCD: Fortran programs for couplings at complex momenta in various analytic QCD models
Ayala, Cesar
2015-01-01T23:59:59.000Z
We provide three Fortran programs which evaluate the QCD analytic (holomorphic) couplings $\\mathcal{A}_{\
mc4qcd: Online Analysis Tool for Lattice QCD
Massimo Di Pierro; Yaoqian Zhong; Brian Schinazi
2010-05-19T23:59:59.000Z
mc4qcd is a web based collaboration tool for analysis of Lattice QCD data. Lattice QCD computations consists of a large scale Markov Chain Monte Carlo. Multiple measurements are performed at each MC step. Our system acquires the data by uploading log files, parses them for results of measurements, filters the data, mines for required information by aggregating results, represents the results as plots and histograms, and it further allows refining and interaction by fitting the results. The system computes moving averages and autocorrelations, builds bootstrap samples and bootstrap errors, and allows modeling the data using Bayesian correlated constrained linear and non-linear fits. It can be scripted to allow real time visualization of results form an ongoing computation. The system is modular and it can be adapted to automating the analysis workflow of different types of MC computations.
QCD Thermodynamics on the Lattice: Recent Results
Carleton DeTar
2010-12-31T23:59:59.000Z
I give a brief introduction to the goals, challenges, and technical difficulties of lattice QCD thermodynamics and present some recent results from the HotQCD collaboration for the crossover temperature, equation of state, and other observables.
Understanding Parton Distributions from Lattice QCD
Dru B. Renner
2005-08-04T23:59:59.000Z
I examine the past lattice QCD calculations of three representative observables, the transverse quark distribution, momentum fraction, and axial charge, and emphasize the prospects for not only quantitative comparison with experiment but also qualitative understanding of QCD.
Generalized Parton Distributions from Lattice QCD
D. B. Renner
2005-01-05T23:59:59.000Z
I review the LHPC Collaboration's lattice QCD calculations of the generalized parton distributions of the nucleon and highlight those aspects of nucleon structure best illuminated by lattice QCD, the nucleon's spin decomposition and transverse quark structure.
Lattice QCD with Domain Decomposition on Intel Xeon Phi Co-Processors
Simon Heybrock; Bálint Joó; Dhiraj D. Kalamkar; Mikhail Smelyanskiy; Karthikeyan Vaidyanathan; Tilo Wettig; Pradeep Dubey
2014-12-08T23:59:59.000Z
The gap between the cost of moving data and the cost of computing continues to grow, making it ever harder to design iterative solvers on extreme-scale architectures. This problem can be alleviated by alternative algorithms that reduce the amount of data movement. We investigate this in the context of Lattice Quantum Chromodynamics and implement such an alternative solver algorithm, based on domain decomposition, on Intel Xeon Phi co-processor (KNC) clusters. We demonstrate close-to-linear on-chip scaling to all 60 cores of the KNC. With a mix of single- and half-precision the domain-decomposition method sustains 400-500 Gflop/s per chip. Compared to an optimized KNC implementation of a standard solver [1], our full multi-node domain-decomposition solver strong-scales to more nodes and reduces the time-to-solution by a factor of 5.
Spectral density of the Dirac operator in two-flavour QCD
Georg P. Engel; Leonardo Giusti; Stefano Lottini; Rainer Sommer
2014-11-24T23:59:59.000Z
We compute the spectral density of the (Hermitean) Dirac operator in Quantum Chromodynamics with two light degenerate quarks near the origin. We use CLS/ALPHA lattices generated with two flavours of O(a)-improved Wilson fermions corresponding to pseudoscalar meson masses down to 190 MeV, and with spacings in the range 0.05-0.08 fm. Thanks to the coverage of parameter space, we can extrapolate our data to the chiral and continuum limits with confidence. The results show that the spectral density at the origin is non-zero because the low modes of the Dirac operator do condense as expected in the Banks-Casher mechanism. Within errors, the spectral density turns out to be a constant function up to eigenvalues of approximately 80 MeV. Its value agrees with the one extracted from the Gell-Mann-Oakes-Renner relation.
Lattice QCD with Domain Decomposition on Intel Xeon Phi Co-Processors
Heybrock, Simon; Joo, Balint; Kalamkar, Dhiraj D.; Smelyanskiy, Mikhail; Vaidyanathan, Karthikeyan; Wettig, Tilo; Dubey, Pradeep
2014-12-01T23:59:59.000Z
The gap between the cost of moving data and the cost of computing continues to grow, making it ever harder to design iterative solvers on extreme-scale architectures. This problem can be alleviated by alternative algorithms that reduce the amount of data movement. We investigate this in the context of Lattice Quantum Chromodynamics and implement such an alternative solver algorithm, based on domain decomposition, on Intel Xeon Phi co-processor (KNC) clusters. We demonstrate close-to-linear on-chip scaling to all 60 cores of the KNC. With a mix of single- and half-precision the domain-decomposition method sustains 400-500 Gflop/s per chip. Compared to an optimized KNC implementation of a standard solver [1], our full multi-node domain-decomposition solver strong-scales to more nodes and reduces the time-to-solution by a factor of 5.
Progress in lattice QCD at finite temperature
Peter Petreczky
2006-06-09T23:59:59.000Z
I review current status of lattice QCD calculations of the deconfining transition at finite temperature and quarkonia spectral functions.
Chris Meyer; for the ATLAS Collaboration
2014-09-15T23:59:59.000Z
Recent QCD results from ATLAS taken at 7 TeV center-of-mass energy using the LHC are presented, including: dijet production, isolated photon production, isolated photon production associated with jets, jet shapes in top-quark pair events, the production cross-section of the phi(1020) meson, and underlying event in jet events. Good agreement with theory predictions is seen, in particular with those made by next-to-leading-order generators. These measurements highlight the importance of precision QCD measurements for improving state-of-the-art theoretical tools and searching for new physics.
Applications of chiral perturbation theory to lattice QCD
Maarten Golterman
2010-05-06T23:59:59.000Z
These notes contain the written version of lectures given at the 2009 Les Houches Summer School "Modern perspectives in lattice QCD: Quantum field theory and high performance computing." The goal is to provide a pedagogical introduction to the subject, and not a comprehensive review. Topics covered include a general introduction, the inclusion of scaling violations in chiral perturbation theory, partial quenching and mixed actions, chiral perturbation theory with heavy kaons, and the effects of finite volume, both in the p- and epsilon-regimes.
Highly Excited and Exotic Meson Spectrum from Dynamical Lattice QCD
Dudek, Jozef J. [Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States); Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States); Edwards, Robert G.; Richards, David G.; Thomas, Christopher E. [Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States); Peardon, Michael J. [School of Mathematics, Trinity College, Dublin 2 (Ireland)
2009-12-31T23:59:59.000Z
Using a new quark-field construction algorithm and a large variational basis of operators, we extract a highly excited isovector meson spectrum on dynamical anisotropic lattices. We show how carefully constructed operators can be used to reliably identify the continuum spin of extracted states, overcoming the reduced cubic symmetry of the lattice. Using this method we extract, with confidence, excited states, states with exotic quantum numbers (0{sup +-}, 1{sup -+}, and 2{sup +-}), and states of high spin, including, for the first time in lattice QCD, spin-four states.
First-principles Calculation of Excited State Spectra in QCD
Dudek, Jozef J. [Jefferson Laboratory, 12000 Jefferson Avenue Suite 1, Newport News, VA 23606 (United States); Department of Physics, Old Dominion University, Norfolk, VA 23529 (United States); Edwards, Robert G.; Richards, David G.; Thomas, Christopher E. [Jefferson Laboratory, 12000 Jefferson Avenue Suite 1, Newport News, VA 23606 (United States); Peardon, Michael J. [School of Mathematics, Trinity College, Dublin 2 (Ireland)
2011-05-24T23:59:59.000Z
Recent progress at understanding the excited state spectra of mesons and baryons is described. I begin by outlining the application of the variational method to compute the spectrum of QCD, and then present results for the excited meson spectrum, with continuum quantum numbers of the states clearly delineated. I emphasise the need to extend the calculation to encompass multi-hadron contributions, and describe a recent calculation of the I = 2{pi}{pi} energy-dependent phase shifts as a precursor to the study of channels with resonant behavior. I conclude with recent results for the low lying baryon spectrum, and the prospects for future calculations.
Thomas D. Cohen
2010-03-15T23:59:59.000Z
It is shown that large Nc QCD must have a Hagedorn spectrum (i.e. a spectrum of hadron which grows exponentially with the hadrons mass) provided that certain technical assumptions concerning the applicability of perturbation theory to a certain class of correlation functions apply. The basic argument exploits the interplay of confinement and asymptotic freedom.
QCD Radiation off Heavy Particles
Torbjörn Sjöstrand
2000-12-15T23:59:59.000Z
An algorithm for an improved description of final-state QCD radiation is introduced. It is matched to the first-order matrix elements for gluon emission in a host of decays, for processes within the Standard Model and the Minimal Supersymmetric extension thereof.
Renormalization in Coulomb gauge QCD
A. Andrasi; J. C. Taylor
2010-10-28T23:59:59.000Z
In the Coulomb gauge of QCD, the Hamiltonian contains a non-linear Christ-Lee term, which may alternatively be derived from a careful treatment of ambiguous Feynman integrals at 2-loop order. We investigate how and if UV divergences from higher order graphs can be consistently absorbed by renormalization of the Christ-Lee term. We find that they cannot.
Basics of QCD Perturbation Theory
Davison E. Soper
1997-01-31T23:59:59.000Z
This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. I also cover some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions.
Behavior of single-scale hard small-x processes in QCD near the black disk limit
Blok, B.; Frankfurt, L. [Department of Physics, Technion--Israel Institute of Technology, 32000 Haifa (Israel); School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Tel Aviv (Israel)
2006-03-01T23:59:59.000Z
We argue that at sufficiently small Bjorken x where pQCD amplitudes rapidly increase with energy and violate probability conservation the shadowing effects in the single-scale small x hard QCD processes can be described by an effective quantum field theory of interacting quasiparticles--perturbative QCD ladders. We find, within the WKB approximation, that the smallness of the QCD coupling constant ensures the hierarchy among many-quasiparticle interactions evaluated within the physical vacuum and, in particular, the dominance in the Lagrangian of the triple quasiparticle interaction. It is explained that the effective field theory considered near the perturbative QCD vacuum contains a tachyon relevant for the divergency of the perturbative QCD series at sufficiently small x. We solve the equations of motion of the effective field theory within the WKB approximation and find the physical vacuum and the transitions between the false (perturbative) and physical vacua. Classical solutions which dominate transitions between the false and physical vacua are kinks that cannot be decomposed into perturbative series over the powers of {alpha}{sub s}. These kinks lead to color inflation and the Bose-Einstein condensation of quasiparticles. The account of the quantum fluctuations around the WKB solution reveals the appearance of the ''massless'' particles--phonons. It is explained that phonons are relevant for the black disk behavior of cross sections of small x processes. The Bose-Einstein condensation of the ladders produces a color network occupying a ''macroscopic'' longitudinal volume. We discuss briefly the possible detection of new QCD effects. We outline albeit briefly the relationship between the small x hard QCD processes and the coherent critical phenomena.
Transition Radiation in QCD matter
Magdalena Djordjevic
2005-12-22T23:59:59.000Z
In ultrarelativistic heavy ion collisions a finite size QCD medium is created. In this paper we compute radiative energy loss to zeroth order in opacity by taking into account finite size effects. Transition radiation occurs on the boundary between the finite size medium and the vacuum, and we show that it lowers the difference between medium and vacuum zeroth order radiative energy loss relative to the infinite size medium case. Further, in all previous computations of light parton radiation to zeroth order in opacity, there was a divergence caused by the fact that the energy loss is infinite in the vacuum and finite in the QCD medium. We show that this infinite discontinuity is naturally regulated by including the transition radiation.
Bhattacharya, Tanmoy
2015-01-01T23:59:59.000Z
Results for the equation of state in 2+1 flavor QCD at zero net baryon density using the Highly Improved Staggered Quark (HISQ) action by the HotQCD collaboration are presented. The strange quark mass was tuned to its physical value and the light (up/down) quark masses fixed to $m_l = 0.05m_s$ corresponding to a pion mass of 160 MeV in the continuum limit. Lattices with temporal extent $N_t=6$, 8, 10 and 12 were used. Since the cutoff effects for $N_t>6$ were observed to be small, reliable continuum extrapolations of the lattice data for the phenomenologically interesting temperatures range $130 \\mathord{\\rm MeV} < T < 400 \\mathord{\\rm MeV}$ could be performed. We discuss statistical and systematic errors and compare our results with other published works.
Tanmoy Bhattacharya; for the HotQCD collaboration
2015-01-30T23:59:59.000Z
Results for the equation of state in 2+1 flavor QCD at zero net baryon density using the Highly Improved Staggered Quark (HISQ) action by the HotQCD collaboration are presented. The strange quark mass was tuned to its physical value and the light (up/down) quark masses fixed to $m_l = 0.05m_s$ corresponding to a pion mass of 160 MeV in the continuum limit. Lattices with temporal extent $N_t=6$, 8, 10 and 12 were used. Since the cutoff effects for $N_t>6$ were observed to be small, reliable continuum extrapolations of the lattice data for the phenomenologically interesting temperatures range $130 \\mathord{\\rm MeV} < T < 400 \\mathord{\\rm MeV}$ could be performed. We discuss statistical and systematic errors and compare our results with other published works.
FermiQCD: A tool kit for parallel lattice QCD applications
Massimo Di Pierro
2001-10-15T23:59:59.000Z
We present here the most recent version of FermiQCD, a collection of C++ classes, functions and parallel algorithms for lattice QCD, based on Matrix Distributed Processing. FermiQCD allows fast development of parallel lattice applications and includes some SSE2 optimizations for clusters of Pentium 4 PCs.
None
2011-10-06T23:59:59.000Z
Modern QCD - Lecture 2 We will start discussing the matter content of the theory and revisit the experimental measurements that led to the discovery of quarks. We will then consider a classic QCD observable, the R-ratio, and use it to illustrate the appearance of UV divergences and the need to renormalize the coupling constant of QCD. We will then discuss asymptotic freedom and confinement. Finally, we will examine a case where soft and collinear infrared divergences appear, will discuss the soft approximation in QCD and will introduce the concept of infrared safe jets.
Light-Front Holographic QCD and Emerging Confinement
Stanley J. Brodsky; Guy F. de Teramond; Hans Gunter Dosch; Joshua Erlich
2015-02-13T23:59:59.000Z
In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here gives a precise interpretation of holographic variables and quantities in AdS in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound states in physical space-time. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large $q^2$ the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low $q^2$ the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.
Light-front holographic QCD and emerging confinement
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Brodsky, Stanley J.; de Téramond, Guy F.; Dosch, Hans Günter; Erlich, Joshua
2015-07-01T23:59:59.000Z
In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. Themore »light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.« less
Light-front holographic QCD and emerging confinement
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Brodsky, Stanley J. [SLAC National Accelerator Laboratory, Stanford, CA (United States); de Téramond, Guy F. [Universidad de Costa Rica, San José, (Costa Rica); Dosch, Hans Günter [Institut für Theoretische Physik, Heidelberg (Germany); Erlich, Joshua [College of William and Mary, Williamsburg, VA (United States)
2015-07-01T23:59:59.000Z
In this report we explore the remarkable connections between light-front dynamics, its holographic mapping to gravity in a higher-dimensional anti-de Sitter (AdS) space, and conformal quantum mechanics. This approach provides new insights into the origin of a fundamental mass scale and the physics underlying confinement dynamics in QCD in the limit of massless quarks. The result is a relativistic light-front wave equation for arbitrary spin with an effective confinement potential derived from a conformal action and its embedding in AdS space. This equation allows for the computation of essential features of hadron spectra in terms of a single scale. The light-front holographic methods described here give a precise interpretation of holographic variables and quantities in AdS space in terms of light-front variables and quantum numbers. This leads to a relation between the AdS wave functions and the boost-invariant light-front wave functions describing the internal structure of hadronic bound-states in physical spacetime. The pion is massless in the chiral limit and the excitation spectra of relativistic light-quark meson and baryon bound states lie on linear Regge trajectories with identical slopes in the radial and orbital quantum numbers. In the light-front holographic approach described here currents are expressed as an infinite sum of poles, and form factors as a product of poles. At large q 2 the form factor incorporates the correct power-law fall-off for hard scattering independent of the specific dynamics and is dictated by the twist. At low q 2 the form factor leads to vector dominance. The approach is also extended to include small quark masses. We briefly review in this report other holographic approaches to QCD, in particular top-down and bottom-up models based on chiral symmetry breaking. We also include a discussion of open problems and future applications.
Quantum field theory and the Standard Model
W. Hollik
2010-12-17T23:59:59.000Z
In this lecture we discuss the basic ingredients for gauge invariant quantum field theories. We give an introduction to the elements of quantum field theory, to the construction of the basic Lagrangian for a general gauge theory, and proceed with the formulation of QCD and the electroweak Standard Model with electroweak symmetry breaking via the Higgs mechanism. The phenomenology of W and Z bosons is discussed and implications for the Higgs boson are derived from comparison with experimental precision data.
Manifest Verification of QCD Gauge Theory
Yu Kun Qian
2008-10-29T23:59:59.000Z
We analyze the magnetic moment of gluon, find if QCD is nongauge SU(3) theory then the magnetic moment of gluon varnishes, but if QCD is gauge theory then the magnetic moment of gluon will not vanishes. The magnetic moment of gluon can be measured by investigate the E-M decay of gluball.
On the behaviour of single scale hard small $x$ processes in QCD near the black disc limit
B. Blok; L. Frankfurt
2006-03-08T23:59:59.000Z
We argue that at sufficiently small Bjorken $x$ where pQCD amplitude rapidly increases with energy and violates probability conservation the shadowing effects in the single-scale small $x$ hard QCD processes can be described by an effective quantum field theory of interacting quasiparticles. The quasiparticles are the perturbative QCD ladders. We find, within the WKB approximation, that the smallness of the QCD coupling constant ensures the hierarchy among many-quasiparticle interactions evaluated within physical vacuum and in particular, the dominance in the Lagrangian of the triple quasiparticle interaction. It is explained that the effective field theory considered near the perturbative QCD vacuum contains a tachyon relevant for the divergency of the perturbative QCD series at sufficiently small $x$. We solve the equations of motion of the effective field theory within the WKB approximation and find the physical vacuum and the transitions between the false (perturbative) and physical vacua. Classical solutions which dominate transitions between the false and physical vacua are kinks that cannot be decomposed into perturbative series over the powers of $\\alpha_s$. These kinks lead to color inflation and the Bose-Einstein condensation of quasiparticles. The account of the quantum fluctuations around the WKB solution reveals the appearance of the "massless" particles-- "phonons". It is explained that "phonons" are relevant for the black disc behaviour of small $x$ processes, leading to a Froissart rise of the cross-section. The condensation of the ladders produces a color network occupying a "macroscopic" longitudinal volume. We discuss briefly the possible detection of new QCD effects.
Lattice QCD and NERSC requirements
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 TablesExports(Journal Article)41clothThe Bonneville PowerTariff Pages default Sign In AboutIsrelocatesLaser Seeding YieldsConference:W56News Â»QCD and
Nuclear Physics from Lattice QCD
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) Natural Gas DeliveredStents -(NEI) SummitNuclearSpringfrom Lattice QCD
QCD Thermodynamics with Improved Actions
Karsch, Frithjof; Engels, J; Joswig, R; Laermann, E; Peikert, A; Petersson, B
1996-01-01T23:59:59.000Z
The thermodynamics of the SU(3) gauge theory has been analyzed with tree level and tadpole improved Symanzik actions. A comparison with the continuum extrapolated results for the standard Wilson action shows that improved actions lead to a drastic reduction of finite cut-off effects already on lattices with temporal extent $N_\\tau=4$. Results for the pressure, the critical temperature, surface tension and latent heat are presented. First results for the thermodynamics of four-flavour QCD with an improved staggered action are also presented. They indicate similarly large improvement factors for bulk thermodynamics.
Nuclear Force from Lattice QCD
Noriyoshi ISHII; Sinya AOKI; Tetsuo HATSUDA
2006-09-30T23:59:59.000Z
The first lattice QCD result on the nuclear force (the NN potential) is presented in the quenched level. The standard Wilson gauge action and the standard Wilson quark action are employed on the lattice of the size 16^3\\times 24 with the gauge coupling beta=5.7 and the hopping parameter kappa=0.1665. To obtain the NN potential, we adopt a method recently proposed by CP-PACS collaboration to study the pi pi scattering phase shift. It turns out that this method provides the NN potentials which are faithful to those obtained in the analysis of NN scattering data. By identifying the equal-time Bethe-Salpeter wave function with the Schroedinger wave function for the two nucleon system, the NN potential is reconstructed so that the wave function satisfies the time-independent Schroedinger equation. In this report, we restrict ourselves to the J^P=0^+ and I=1 channel, which enables us to pick up unambiguously the ``central'' NN potential V_{central}(r). The resulting potential is seen to posses a clear repulsive core of about 500 MeV at short distance (r < 0.5 fm). Although the attraction in the intermediate and long distance regions is still missing in the present lattice set-up, our method is appeared to be quite promising in reconstructing the NN potential with lattice QCD.
AdS/QCD at finite density and temperature
Kim, Y., E-mail: ykim@apctp.org [Pohang University of Science and Technology, Asia Pacific Center for Theoretical Physics and Department of Physics (Korea, Republic of)
2012-07-15T23:59:59.000Z
We review some basics of AdS/QCD following a non-standard path and list a few results from AdS/QCD or holographic QCD. The non-standard path here is to use the analogy of the way one obtains an effective model of QCD like linear sigma model and the procedure to construct an AdS/QCD model based on the AdS/CFT dictionary.
J/psi production and polarization
Maddalena Frosini; for the LHCb Collaboration
2012-08-31T23:59:59.000Z
The study of the production of heavy quarkonium is crucial for a thorough understanding of Quantum Chromodynamics (QCD). This note reports the measurements of the J\\psi, \\chi_c and double charm production cross section, and discusses the prospects for the J/psi polarization at LHCb.
The Matrix Element Method and QCD Radiation
J. Alwall; A. Freitas; O. Mattelaer
2011-04-22T23:59:59.000Z
The matrix element method (MEM) has been extensively used for the analysis of top-quark and W-boson physics at the Tevatron, but in general without dedicated treatment of initial state QCD radiation. At the LHC, the increased center of mass energy leads to a significant increase in the amount of QCD radiation, which makes it mandatory to carefully account for its effects. We here present several methods for inclusion of QCD radiation effects in the MEM, and apply them to mass determination in the presence of multiple invisible particles in the final state. We demonstrate significantly improved results compared to the standard treatment.
Recent Progress in Lattice QCD Thermodynamics
Carleton DeTar
2008-11-14T23:59:59.000Z
This review gives a critical assessment of the current state of lattice simulations of QCD thermodynamics and what it teaches us about hot hadronic matter. It outlines briefly lattice methods for studying QCD at nonzero temperature and zero baryon number density with particular emphasis on assessing and reducing cutoff effects. It discusses a variety of difficulties with methods for determining the transition temperature. It uses results reported recently in the literature and at this conference for illustration, especially those from a major study carried out by the HotQCD collaboration.
Chiral dynamics in the low-temperature phase of QCD
Bastian B. Brandt; Anthony Francis; Harvey B. Meyer; Daniel Robaina
2014-10-22T23:59:59.000Z
We investigate the low-temperature phase of QCD and the crossover region with two light flavors of quarks. The chiral expansion around the point $(T, m_q = 0)$ in the temperature vs. quark-mass plane indicates that a sharp real-time excitation exists with the quantum numbers of the pion. We determine its dispersion relation and test the applicability of the chiral expansion. The time-dependent correlators are also analyzed using the Maximum Entropy Method (MEM), yielding consistent results. Finally, we test the predictions of ordinary chiral perturbation theory around the point $(T = 0, m_q = 0)$ for the temperature dependence of static observables. Around the crossover temperature, we find that all quantities considered depend only mildly on the quark mass in the considered range 8MeV $\\leq \\bar{m}^{\\bar{\\text{MS}}} \\leq$ 15MeV.
Toward the excited meson spectrum of dynamical QCD
Dudek, Jozef J. [Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States); Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States); Edwards, Robert G.; Richards, David G.; Thomas, Christopher E. [Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States); Peardon, Michael J. [School of Mathematics, Trinity College, Dublin 2 (Ireland)
2010-08-01T23:59:59.000Z
We present a detailed description of the extraction of the highly excited isovector meson spectrum on dynamical anisotropic lattices using a new quark-field construction algorithm and a large variational basis of operators. With careful operator construction, the combination of these techniques is used to identify the continuum spin of extracted states reliably, overcoming the reduced rotational symmetry of the cubic lattice. Excited states, states with exotic quantum numbers (0{sup +-}, 1{sup -+} and 2{sup +-}), and states of high spin are resolved, including, for the first time in a lattice QCD calculation, spin-four states. The determinations of the spectrum of isovector mesons and kaons are performed on dynamical lattices with two volumes and with pion masses down to {approx}400 MeV, with statistical precision typically at or below 1% even for highly excited states.
QCD. What else is needed for the Proton Structure Function?
Y. S. Kim
2014-08-18T23:59:59.000Z
While QCD can provide corrections to the parton distribution function, it cannot produce the distribution. Where is then the starting point for the proton structure function? The only known source is the quark-model wave function for the proton at rest. The harmonic oscillator is used for the trial wave function. When Lorentz-boosted, this wave function exhibits all the peculiarities of Feynman's parton picture. The time-separation between the quarks plays the key role in the boosting process. This variable is hidden in the present form of quantum mechanics, and the failure to measure it leads to an increase in entropy. This leads to a picture of boiling quarks which become partons in their plasma state.
QCD Collisional Energy Loss Reexamined
Peshier, A. [Institut fuer Theoretische Physik, Universitaet Giessen, 35392 Giessen (Germany)
2006-11-24T23:59:59.000Z
It is shown that at a large temperature and E{yields}{infinity} the QCD collisional energy loss reads dE/dx{approx}{alpha}(m{sub D}{sup 2})T{sup 2}. Compared to previous approaches, which led to dE{sup B}/dx{approx}{alpha}{sup 2}T{sup 2}ln(ET/m{sub D}{sup 2}) similar to the Bethe-Bloch formula in QED, we take into account the running of the strong coupling. As one significant consequence, due to asymptotic freedom, dE/dx becomes E independent for large parton energies. Some implications with regard to heavy ion collisions are pointed out.
T. T. Takahashi; T. Doi; H. Suganuma
2006-01-05T23:59:59.000Z
We perform the quenched lattice QCD analysis on the nuclear force (baryon-baryon interactions). We employ $20^3\\times 24$ lattice at $\\beta=5.7$ ($a\\simeq 0.19$ fm) with the standard gauge action and the Wilson quark action with the hopping parameters $\\kappa=0.1600, 0.1625, 0.1650$, and generate about 200 gauge configurations. We measure the temporal correlators of the two-baryon system which consists of heavy-light-light quarks. We extract the inter-baryon force as a function of the relative distance $r$. We also evaluate the contribution to the nuclear force from each ``Feynman diagram'' such as the quark-exchange diagram individually, and single out the roles of Pauli-blocking effects or quark exchanges in the inter-baryon interactions.
QCD Matrix Elements + Parton Showers
S. Catani; F. Krauss; R. Kuhn; B. R. Webber
2001-09-25T23:59:59.000Z
We propose a method for combining QCD matrix elements and parton showers in Monte Carlo simulations of hadronic final states in $e^+e^-$ annihilation. The matrix element and parton shower domains are separated at some value $y_{ini}$ of the jet resolution, defined according to the $k_T$-clustering algorithm. The matrix elements are modified by Sudakov form factors and the parton showers are subjected to a veto procedure to cancel dependence on $y_{ini}$ to next-to-leading logarithmic accuracy. The method provides a leading-order description of hard multi-jet configurations together with jet fragmentation, while avoiding the most serious problems of double counting. We present first results of an approximate implementation using the event generator APACIC++.
Simplifying Multi-Jet QCD Computation
Peskin, Michael E.; /SLAC
2011-11-04T23:59:59.000Z
These lectures give a pedagogical discussion of the computation of QCD tree amplitudes for collider physics. The tools reviewed are spinor products, color ordering, MHV amplitudes, and the Britto-Cachazo-Feng-Witten recursion formula.
None
2011-10-06T23:59:59.000Z
Modern QCD - Lecture 4 We will consider some processes of interest at the LHC and will discuss the main elements of their cross-section calculations. We will also summarize the current status of higher order calculations.
Lattice QCD at the end of 2003
Thomas DeGrand
2003-12-17T23:59:59.000Z
I review recent developments in lattice QCD. I first give an overview of its formalism, and then discuss lattice discretizations of fermions. We then turn to a description of the quenched approximation and why it is disappearing as a vehicle for QCD phenomenology. I describe recent claims for progress in simulations which include dynamical fermions and the interesting theoretical problems they raise. I conclude with brief descriptions of the calculations of matrix elements in heavy flavor systems and for kaons.
Two Dimensional QCD is a String Theory
David J. Gross; Washington Taylor
1993-01-18T23:59:59.000Z
The partition function of two dimensional QCD on a Riemann surface of area $A$ is expanded as a power series in $1/N$ and $A$. It is shown that the coefficients of this expansion are precisely determined by a sum over maps from a two dimensional surface onto the two dimensional target space. Thus two dimensional QCD has a simple interpretation as a closed string theory.
Thermodynamics of (2+1)-flavor QCD
C. Schmidt; T. Umeda
2006-09-21T23:59:59.000Z
We report on the status of our QCD thermodynamics project. It is performed on the QCDOC machine at Brookhaven National Laboratory and the APEnext machine at Bielefeld University. Using a 2+1 flavor formulation of QCD at almost realistic quark masses we calculated several thermodynamical quantities. In this proceeding we show the susceptibilites of the chiral condensate and the Polyakov loop, the static quark potential and the spatial string tension.
Quantum Chaos & Quantum Computers
D. L. Shepelyansky
2000-06-15T23:59:59.000Z
The standard generic quantum computer model is studied analytically and numerically and the border for emergence of quantum chaos, induced by imperfections and residual inter-qubit couplings, is determined. This phenomenon appears in an isolated quantum computer without any external decoherence. The onset of quantum chaos leads to quantum computer hardware melting, strong quantum entropy growth and destruction of computer operability. The time scales for development of quantum chaos and ergodicity are determined. In spite the fact that this phenomenon is rather dangerous for quantum computing it is shown that the quantum chaos border for inter-qubit coupling is exponentially larger than the energy level spacing between quantum computer eigenstates and drops only linearly with the number of qubits n. As a result the ideal multi-qubit structure of the computer remains rather robust against imperfections. This opens a broad parameter region for a possible realization of quantum computer. The obtained results are related to the recent studies of quantum chaos in such many-body systems as nuclei, complex atoms and molecules, finite Fermi systems and quantum spin glass shards which are also reviewed in the paper.
Jet physics and strong coupling at HERA
Maxime Gouzevitch
2009-06-05T23:59:59.000Z
Jet production in electron-proton scattering at HERA provides an important testing ground for Quantum Chromodynamics (QCD). The inclusive jet and multi-jet cross sections recently measured by H1 and ZEUS collaborations allow a precise determination of the strong coupling and test of its running. Additionally, a measurement of the angular correlations in the 3-jet events gives a handle on the fundamental gauge structure of the QCD.
Heavy Flavour Production at HERA
Benno List; for the H1; ZEUS Collaborations
2006-05-19T23:59:59.000Z
The production of charm and beauty quarks in ep collisions at HERA has been studied by the H1 and ZEUS collaborations. Charm production is generally well described in total rate and in shape by next to leading order (NLO) calculations in perturbative quantum chromodynamics (QCD), although in specific phase space corners the NLO calculations underestimate the observed cross sections. More and more beauty production data are becoming available. For this process, NLO QCD predictions tend to be lower than the measurements.
Study of hadronic event-shape variables in multijet final states in pp collisions at ?s = 7 TeV
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Khachatryan, Vardan
2014-10-14T23:59:59.000Z
Event-shape variables, which are sensitive to perturbative and nonperturbative aspects of quantum chromodynamic (QCD) interactions, are studied in multijet events recorded in proton-proton collisions at ?s = 7 TeV. Events are selected with at least one jet with transverse momentum pT > 110 GeV and pseudorapidity |?| –1. The distributions of five event-shape variables in various leading jet pT ranges are compared to predictions from different QCD Monte Carlo event generators.
Electromagnetically superconducting phase of QCD vacuum induced by strong magnetic field
Chernodub, M. N. [CNRS, Laboratoire de Mathematiques et Physique Theorique, Universite Francois-Rabelais Tours, Federation Denis Poisson, Parc de Grandmont, 37200 Tours (France); Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium)
2011-05-23T23:59:59.000Z
In this talk we discuss our recent suggestion that the QCD vacuum in a sufficiently strong magnetic field (stronger than 10{sup 16} Tesla) may undergo a spontaneous transition to an electromagnetically superconducting state. The possible superconducting state is anisotropic (the vacuum exhibits superconductivity only along the axis of the uniform magnetic field) and inhomogeneous (in the transverse directions the vacuum structure shares similarity with the Abrikosov lattice of an ordinary type-II superconductor). The electromagnetic superconductivity of the QCD vacuum is suggested to occur due to emergence of specific quark-antiquark condensates which carry quantum numbers of electrically charged rho mesons. A Lorentz-covariant generalization of the London transport equations for the magnetic-field-induced superconductivity is given.
Two-Nucleon Higher Partial-Wave Scattering from Lattice QCD
Berkowitz, Evan; Nicholson, Amy; Joo, Balint; Rinaldi, Enrico; Strother, Mark; Vranas, Pavlos M; Walker-Loud, Andre
2015-01-01T23:59:59.000Z
We present a determination of nucleon-nucleon scattering phase shifts for l>=0. The S,P,D and F phase shifts for both the spin-triplet and spin-singlet channels are computed for the first time with lattice Quantum ChromoDynamics. This required the design and implementation of novel lattice methods involving displaced sources and momentum-space cubic sinks. To demonstrate the utility of our approach, the calculations were performed in the SU(3)-flavor limit where the light quark masses have been tuned to the physical strange quark mass, corresponding to m_pi = m_K ~ 800 MeV. Two spatial volumes of V ~ (3.5 fm)^3 and V ~ (4.6 fm)^3 were used. The finite-volume spectrum is extracted from the exponential falloff of the correlation functions. Said spectrum is mapped onto the infinite volume phase shifts using the generalization of the Luscher formalism for two-nucleon systems.
Synthetic Running Coupling of QCD
Aleksey I. Alekseev
2006-02-19T23:59:59.000Z
Based on a study of the analytic running coupling obtained from the standard perturbation theory results up to four-loop order, the QCD ``synthetic'' running coupling \\alpha_{syn} is built. In so doing the perturbative time-like discontinuity is preserved and nonperturbative contributions not only remove the nonphysical singularities of the perturbation theory in the infrared region but also decrease rapidly in the ultraviolet region. In the framework of the approach, on the one hand, the running coupling is enhanced at zero and, on the other hand, the dynamical gluon mass m_g arises. Fixing the parameter which characterize the infrared enhancement corresponding to the string tension \\sigma and normalization, say, at M_\\tau completely define the synthetic running coupling. In this case the dynamical gluon mass appears to be fixed and the higher loop stabilization property of m_g is observed. For \\sigma = (0.42 GeV)^2 and \\alpha_{syn}(M^2_\\tau) = 0.33 \\pm 0.01 it is obtained that m_g = 530 \\pm 80 MeV.
Jet Quenching from QCD Evolution
Chien, Yang-Ting; Kang, Zhong-Bo; Ovanesyan, Grigory; Vitev, Ivan
2015-01-01T23:59:59.000Z
Recent advances in soft-collinear effective theory with Glauber gluons have led to the development of a new method that gives a unified description of inclusive hadron production in reactions with nucleons and heavy nuclei. We show how this approach, based on the generalization of the DGLAP evolution equations to include final-state medium-induced parton showers, can be combined with initial-state effects for applications to jet quenching phenomenology. We demonstrate that the traditional parton energy loss calculations can be regarded as a special soft-gluon emission limit of the general QCD evolution framework. We present phenomenological comparison of the SCET$_{\\rm G}$-based results on the suppression of inclusive charged hadron and neutral pion production in $\\sqrt{s_{NN}}=2.76$ TeV lead-lead collisions at the Large Hadron Collider to experimental data. We also show theoretical predictions for the upcoming $\\sqrt{s_{NN}} \\simeq 5.1$ TeV Pb+Pb run at the LHC.
Cosmological and astrophysical aspects of finite-density QCD
Dominik J. Schwarz
1998-07-23T23:59:59.000Z
The different phases of QCD at finite temperature and density lead to interesting effects in cosmology and astrophysics. In this work I review some aspects of the cosmological QCD transition and of astrophysics at high baryon density.
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 ...
Distinguishing exotic states from scattering states in lattice QCD
Sigaev, Dmitry
2008-01-01T23:59:59.000Z
This work explores the problem of distinguishing potentially interesting new exotic states in QCD from conventional scattering states using lattice QCD, and addresses the specific case of the search for localized resonances ...
QCD at nonzero chemical potential: recent progress on the lattice
Gert Aarts; Felipe Attanasio; Benjamin Jäger; Erhard Seiler; Denes Sexty; Ion-Olimpiu Stamatescu
2014-12-02T23:59:59.000Z
We summarise recent progress in simulating QCD at nonzero baryon density using complex Langevin dynamics. After a brief outline of the main idea, we discuss gauge cooling as a means to control the evolution. Subsequently we present a status report for heavy dense QCD and its phase structure, full QCD with staggered quarks, and full QCD with Wilson quarks, both directly and using the hopping parameter expansion to all orders.
The Electron-Ion Collider Science Case
Richard G. Milner
2014-05-27T23:59:59.000Z
For the first time, physicists are in the position to precisely study a fully relativistic quantum field theory: Quantum ChromoDynamics (QCD). QCD is a central element of the Standard Model and provides the theoretical framework for understanding the strong interaction. This demands a powerful new electron microscope to probe the virtual particles of QCD. Ab initio calculations using lattice gauge theory on the world's most powerful supercomputers are essential for comparison with the data. The new accelerator and computing techniques demand aggressive development of challenging, innovative technologies.
Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.
2011-01-10T23:59:59.000Z
AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.
Lepton asymmetry and the cosmic QCD transition
Dominik J Schwarz; Maik Stuke
2010-09-29T23:59:59.000Z
We study the influence of lepton asymmetry on the evolution of the early Universe. The lepton asymmetry $l$ is poorly constrained by observations and might be orders of magnitude larger than the baryon asymmetry $b$, $|l|/b \\leq 2\\times 10^8$. We find that lepton asymmetries that are large compared to the tiny baryon asymmetry, can influence the dynamics of the QCD phase transition significantly. The cosmic trajectory in the $\\mu_B-T$ phase diagram of strongly interacting matter becomes a function of lepton (flavour) asymmetry. Large lepton asymmetry could lead to a cosmic QCD phase transition of first order.
Testing Algorithms for Finite Temperature Lattice QCD
M. Cheng; M. A. Clark; C. Jung; R. D. Mawhinney
2006-08-23T23:59:59.000Z
We discuss recent algorithmic improvements in simulating finite temperature QCD on a lattice. In particular, the Rational Hybrid Monte Carlo(RHMC) algorithm is employed to generate lattice configurations for 2+1 flavor QCD. Unlike the Hybrid R Algorithm, RHMC is reversible, admitting a Metropolis accept/reject step that eliminates the $\\mathcal{O}(\\delta t^2)$ errors inherent in the R Algorithm. We also employ several algorithmic speed-ups, including multiple time scales, the use of a more efficient numerical integrator, and Hasenbusch pre-conditioning of the fermion force.
Experimental Study of Nucleon Structure and QCD
Jian-Ping Chen
2012-03-01T23:59:59.000Z
Overview of Experimental Study of Nucleon Structure and QCD, with focus on the spin structure. Nucleon (spin) Structure provides valuable information on QCD dynamics. A decade of experiments from JLab yields these exciting results: (1) valence spin structure, duality; (2) spin sum rules and polarizabilities; (3) precision measurements of g{sub 2} - high-twist; and (4) first neutron transverse spin results - Collins/Sivers/A{sub LT}. There is a bright future as the 12 GeV Upgrade will greatly enhance our capability: (1) Precision determination of the valence quark spin structure flavor separation; and (2) Precision extraction of transversity/tensor charge/TMDs.
Automation of one-loop QCD corrections
Valentin Hirschi; Rikkert Frederix; Stefano Frixione; Maria Vittoria Garzelli; Fabio Maltoni; Roberto Pittau
2013-05-14T23:59:59.000Z
We present the complete automation of the computation of one-loop QCD corrections, including UV renormalization, to an arbitrary scattering process in the Standard Model. This is achieved by embedding the OPP integrand reduction technique, as implemented in CutTools, into the MadGraph framework. By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the fully automatic computation of any infrared-safe observable at the next-to-leading order in QCD is attained. We demonstrate the flexibility and the reach of our method by calculating the production rates for a variety of processes at the 7 TeV LHC.
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.
QCDLAB: Designing Lattice QCD Algorithms with MATLAB
Artan Borici
2006-10-09T23:59:59.000Z
This paper introduces QCDLAB, a design and research tool for lattice QCD algorithms. The tool, a collection of MATLAB functions, is based on a ``small-code'' and a ``minutes-run-time'' algorithmic design philosophy. The present version uses the Schwinger model on the lattice, a great simplification, which shares many features and algorithms with lattice QCD. A typical computing project using QCDLAB is characterised by short codes, short run times, and the ability to make substantial changes in a few seconds. QCDLAB 1.0 can be downloaded from the QCDLAB project homepage {\\tt http://phys.fshn.edu.al/qcdlab.html}.
QUANTUM CHAOS IN QUANTUM NETWORKS()
Shepelyansky, Dima
QUANTUM CHAOS IN QUANTUM NETWORKS() Chepelianskii Alexei LycÂ´ee Pierre de Fermat and Quantware MIPS Computers and Quantum Chaos", June 28 - 30, 2001, Villa Olmo, Como, Italy #12;SHORT DESCRIPTION OF THE RESULTS Quantum chaos in a quantum small world We introduce and study a quantum small world model
Jet Quenching in High Energy Heavy Ion Collisions by QCD Synchrotron-like Radiation
E. V. Shuryak; I. Zahed
2002-07-12T23:59:59.000Z
We consider synchrotron-like radiation in QCD by generalizing Schwinger's treatment of quantum synchrotron radiation in QED to the case of a constant chromomagnetic field. We suggest a novel mechanism for {\\em jet quenching} in heavy ion collisions, whereby high-$p_t$ partons get depleted through strong (classical) color fields. The latters are encountered in the color glass condensate or in the form of expanding shells of exploding sphalerons. Unlike bremsstrahlung radiation through multiple soft rescattering, synchrotron radiation converts a jet into a wide shower of soft gluons. We estimate the energy loss through this mechanism and suggest that it contributes significantly to the unexpectedly strong jet quenching observed at RHIC.
Running anti-de Sitter radius from QCD-like strings
Yu-tin Huang; Warren Siegel
2007-07-10T23:59:59.000Z
We consider renormalization effects for a bosonic QCD-like string, whose partons have $1/p^{2}$ propagators instead of Gaussian. Classically this model resembles (the bosonic part of) the projective light-cone (zero-radius) limit of a string on an AdS${}_5$ background, where Schwinger parameters give rise to the fifth dimension. Quantum effects generate dynamics for this dimension, producing an AdS${}_5$ background with a running radius. The projective light-cone is the high-energy limit: Holography is enforced dynamically.
Visualization Tools for Lattice QCD - Final Report
Massimo Di Pierro
2012-03-15T23:59:59.000Z
Our research project is about the development of visualization tools for Lattice QCD. We developed various tools by extending existing libraries, adding new algorithms, exposing new APIs, and creating web interfaces (including the new NERSC gauge connection web site). Our tools cover the full stack of operations from automating download of data, to generating VTK #12;files (topological charge, plaquette, Polyakov lines, quark and meson propagators, currents), to turning the VTK #12;files into images, movies, and web pages. Some of the tools have their own web interfaces. Some Lattice QCD visualization have been created in the past but, to our knowledge, our tools are the only ones of their kind since they are general purpose, customizable, and relatively easy to use. We believe they will be valuable to physicists working in the #12;field. They can be used to better teach Lattice QCD concepts to new graduate students; they can be used to observe the changes in topological charge density and detect possible sources of bias in computations; they can be used to observe the convergence of the algorithms at a local level and determine possible problems; they can be used to probe heavy-light mesons with currents and determine their spatial distribution; they can be used to detect corrupted gauge configurations. There are some indirect results of this grant that will benefit a broader audience than Lattice QCD physicists.
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.
Dual condensate and QCD phase transition
Zhang Bo; Bruckmann, Falk [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Fodor, Zoltan; Szabo, Kalman K. [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42119 (Germany); Gattringer, Christof [Institut fuer Physik, Universitaet Graz, Universitaetsplatz 5, A-8010 Graz (Austria)
2011-05-23T23:59:59.000Z
The dual condensate is a new QCD phase transition order parameter, which connnects confinement and chiral symmetry breaking as different mass limits. We discuss the relation between the fermion spectrum at general boundary conditions and the dual condensate and show numerical results for the latter from unquenched SU(3) lattice configurations.
Challenges facing holographic models of QCD
Thomas D. Cohen
2008-05-30T23:59:59.000Z
This paper, written in memory of Manoj Banerjee, takes a critical look at holographic models of QCD focusing on ``practical'' models in which the five dimensional theory is treated classically. A number of theoretical and phenomenological challenges to the approach are discussed.
Nuclear chiral dynamics and phases of QCD
Wolfram Weise
2012-01-04T23:59:59.000Z
This presentation starts with a brief review of our current picture of QCD phases, derived from lattice QCD thermodynamics and from models based on the symmetries and symmetry breaking patterns of QCD. Typical approaches widely used in this context are the PNJL and chiral quark-meson models. It is pointed out, however, that the modeling of the phase diagram in terms of quarks as quasiparticles misses important and well known nuclear physics constraints. In the hadronic phase of QCD governed by confinement and spontaneously broken chiral symmetry, in-medium chiral effective field theory is the appropriate framework, with pions and nucleons as active degrees of freedom. Nuclear chiral thermodynamics is outlined and the liquid-gas phase transition is described. The density and temperature dependence of the chiral condensate is deduced. As a consequence of two- and three-body correlations in the nuclear medium, no tendency towards a first-order chiral phase transition is found at least up to twice the baryon density of normal nuclear matter and up to temperatures of about 100 MeV. Isospin-asymmetric nuclear matter and neutron matter are also discussed. An outlook is given on new tightened constraints for the equation-of-state of cold and highly compressed matter as implied by a recently observed two-solar-mass neutron star.
Heavy flavor physics from lattice QCD
Tetsuya Onogi
2006-10-24T23:59:59.000Z
I review the recent status of heavy flavor physics results from lattice QCD. In particular, I focus on the heavy-light decay constants, the bag parameters, the form factors, and the bottom quark mass. New progresses in theoretical methods are also reviewed.
The QCD Running Coupling and its Measurement
Guido Altarelli
2013-03-25T23:59:59.000Z
In this lecture, after recalling the basic definitions and facts about the running coupling in QCD, I present a critical discussion of the methods for measuring $\\alpha_s$ and select those that appear to me as the most reliably precise
QCD parton model at collider energies
Ellis, R.K.
1984-09-01T23:59:59.000Z
Using the example of vector boson production, the application of the QCD improved parton model at collider energies is reviewed. The reliability of the extrapolation to SSC energies is assessed. Predictions at ..sqrt..S = 0.54 TeV are compared with data. 21 references.
None
2011-10-06T23:59:59.000Z
Modern QCD - Lecture 3 We will introduce processes with initial-state hadrons and discuss parton distributions, sum rules, as well as the need for a factorization scale once radiative corrections are taken into account. We will then discuss the DGLAP equation, the evolution of parton densities, as well as ways in which parton densities are extracted from data.
Lambda-nucleon force from lattice QCD
Nemura, H; Aoki, S; Hatsuda, T
2008-01-01T23:59:59.000Z
We study the $\\Lambda$-nucleon ($\\Lambda N$) force by using lattice QCD. The Bethe-Salpeter amplitude is calculated for the lowest scattering state of the $\\Lambda N$ so as to obtain the $\\Lambda N$ potential. The numerical calculation is twofold: (i) Full lattice QCD by using 2+1 flavor PACS-CS gauge configurations with, $\\beta=1.9$, corresponding to the lattice spacing of $a=0.0907(13)$ fm, on a $32^3\\times 64$ lattice. A set of parameter $(\\kappa_{ud},\\kappa_s)=(0.13770,0.13640)$ is used, which corresponds to $m_\\pi\\approx 300$ MeV and $m_K\\approx 594$ MeV. The spatial lattice volume corresponds to (2.86 fm)$^3$. (ii) Quenched lattice QCD with $\\beta=5.7$, the lattice spacing of $a=0.1416(9)$ fm, on the $32^3\\times48$ lattice. Two sets of hopping parameters $(\\kappa_{ud},\\kappa_s)=(0.1665,0.1643),(0.1670,0.1643)$ are used. The spatial lattice volume is (4.5 fm)$^3$. For the full QCD, we find that the $\\Lambda p$ has a relatively strong (weak) repulsive core in the $^1S_0$ ($^3S_1$) channel at short distanc...
Basics of QCD Perturbation Theory: TASI 2000
Davison E. Soper
2000-11-21T23:59:59.000Z
This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. I also cover some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions.
New formalism for QCD parton showers
Stefan Gieseke; Philip Stephens; Bryan Webber
2003-10-09T23:59:59.000Z
We present a new formalism for parton shower simulation of QCD jets, which incorporates the following features: invariance under boosts along jet axes, improved treatment of heavy quark fragmentation, angular-ordered evolution with soft gluon coherence, more accurate soft gluon angular distributions, and better coverage of phase space. It is implemented in the new HERWIG++ event generator.
Combining QCD Matrix Elements and Parton Showers
B. R. Webber
2000-05-04T23:59:59.000Z
A new method for combining QCD matrix elements and parton showers in Monte Carlo simulations of hadronic final states is outlined. The aim is to provide at least a leading-order description of all hard multi-jet configurations together with jet fragmentation to next-to-leading logarithmic accuracy, while avoiding the most serious problems of double counting.
Topology in QCD and the axion abundance
Kitano, Ryuichiro
2015-01-01T23:59:59.000Z
The temperature dependence of the topological susceptibility (chi_t) in QCD essentially determines the abundance of the QCD axion in the Universe, and is commonly estimated, based on the instanton picture, to be a certain negative power of temperature. While lattice QCD should be able to check the instanton picture in principle, the region of the temperature where lattice calculations of chi_t are reliable is rather limited in practice, because existing methods on the lattice will probably fail when chi_t decreases rapidly with temperatures. In this work, two exploratory studies are presented. First, to realize the limitation of temperature we perform lattice calculations of chi_t in the quenched approximation and find that it becomes difficult with a given resource when T > 2 T_c. A possible way out is proposed and some test calculations are given. The absolute value and the temperature dependence of chi_t in real QCD can be significantly different from that in the quenched approximation, and is not well est...
Topology in QCD and the axion abundance
Ryuichiro Kitano; Norikazu Yamada
2015-06-01T23:59:59.000Z
The temperature dependence of the topological susceptibility (chi_t) in QCD essentially determines the abundance of the QCD axion in the Universe, and is commonly estimated, based on the instanton picture, to be a certain negative power of temperature. While lattice QCD should be able to check the instanton picture in principle, the region of the temperature where lattice calculations of chi_t are reliable is rather limited in practice, because existing methods on the lattice will probably fail when chi_t decreases rapidly with temperatures. In this work, two exploratory studies are presented. First, to realize the limitation of temperature we perform lattice calculations of chi_t in the quenched approximation and find that it becomes difficult with a given resource when T > 2 T_c. A possible way out is proposed and some test calculations are given. The absolute value and the temperature dependence of chi_t in real QCD can be significantly different from that in the quenched approximation, and is not well established over a wide range of the temperature above its critical value. Motivated by this fact and precedent arguments which disagree with the conventional instanton picture, we estimate the axion abundance in an extreme case where chi_t decreases much faster than the conventional power-like function. We find a significant enhancement of the axion abundance in such a case.
Reweighting QCD simulations with dynamical overlap fermions
Thomas DeGrand
2008-10-03T23:59:59.000Z
I apply a recently developed algorithm for reweighting simulations of lattice QCD from one quark mass to another to simulations performed with overlap fermions in the epsilon regime. I test it by computing the condensate from distributions of the low lying eigenvalues of the Dirac operator. Results seem favorable.
QCD thermodynamics with dynamical overlap fermions
S. Borsanyi; Y. Delgado; S. Durr; Z. Fodor; S. D. Katz; S. Krieg; T. Lippert; D. Nogradi; K. K. Szabo
2012-08-02T23:59:59.000Z
We study QCD thermodynamics using two flavors of dynamical overlap fermions with quark masses corresponding to a pion mass of 350 MeV. We determine several observables on N_t=6 and 8 lattices. All our runs are performed with fixed global topology. Our results are compared with staggered ones and a nice agreement is found.
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.
QCD evolution equations from conformal symmetry
V. M. Braun; A. N. Manashov
2014-08-28T23:59:59.000Z
QCD evolution equations in $\\text{MS}$-like schemes can be recovered from the same equations in a modified theory, QCD in non-integer $d=4-2\\epsilon$ dimensions, which enjoys exact scale and conformal invariance at the critical point. Restrictions imposed by the conformal symmetry of the modified theory allow one to obtain complete evolution kernels in integer (physical) dimensions at the given order of perturbation theory from the spectrum of anomalous dimensions added by the calculation of the special conformal anomaly at one order less. We use this technique to derive two-loop evolution equations for flavor-nonsinglet quark-antiquark light-ray operators that encode the scale dependence of generalized hadron parton distributions.
Nuclear physics from strong coupling QCD
Michael Fromm; Philippe de Forcrand
2009-12-14T23:59:59.000Z
The strong coupling limit (beta_gauge = 0) of QCD offers a number of remarkable research possibilities, of course at the price of large lattice artifacts. Here, we determine the complete phase diagram as a function of temperature T and baryon chemical potential mu_B, for one flavor of staggered fermions in the chiral limit, with emphasis on the determination of a tricritical point and on the T ~ 0 transition to nuclear matter. The latter is known to happen for mu_B substantially below the baryon mass, indicating strong nuclear interactions in QCD at infinite gauge coupling. This leads us to studying the properties of nuclear matter from first principles. We determine the nucleon-nucleon potential in the strong coupling limit, as well as masses m_A of nuclei as a function of their atomic number A. Finally, we clarify the origin of nuclear interactions at strong coupling, which turns out to be a steric effect.
Report of the QCD Working Group
A. Ballestrero; P. Bambade; S. Bravo; M. Cacciari; M. Costa; W. deBoer; G. Dissertori; U. Flagmeyer; J. Fuster; K. Hamacher; F. Krauss; R. Kuhn; L. Lonnblad; S. Marti; J. Rehn; G. Rodrigo; M. H. Seymour; T. Sjostrand; Z. Trocsanyi; B. R. Webber
2000-07-04T23:59:59.000Z
The activities of the QCD working group concentrated on improving the understanding and Monte Carlo simulation of multi-jet final states due to hard QCD processes at LEP, i.e. quark-antiquark plus multi-gluon and/or secondary quark production, with particular emphasis on four-jet final states and b-quark mass effects. Specific topics covered are: relevant developments in the main event generators PYTHIA, HERWIG and ARIADNE; the new multi-jet generator APACIC++; description and tuning of inclusive (all-flavour) jet rates; quark mass effects in the three- and four-jet rates; mass, higher-order and hadronization effects in four-jet angular and shape distributions; b-quark fragmentation and gluon splitting into b-quarks.
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.
Electromagnetic and spin polarisabilities in lattice QCD
W. Detmold; B. C. Tiburzi; A. Walker-Loud
2006-10-02T23:59:59.000Z
We discuss the extraction of the electromagnetic and spin polarisabilities of nucleons from lattice QCD. We show that the external field method can be used to measure all the electromagnetic and spin polarisabilities including those of charged particles. We then turn to the extrapolations required to connect such calculations to experiment in the context of chiral perturbation theory, finding a strong dependence on the lattice volume and quark masses.
QCD, Symmetry Breaking and the Random Lattice
Saul D. Cohen
2006-02-15T23:59:59.000Z
According to the Nielsen-Ninomiya No-Go theorem, the doubling of fermions on the lattice cannot be suppressed in a chiral theory. Whereas Wilson and staggered fermions suppress doublers with explicit breaking of chiral symmetry, the random lattice does so by spontaneous chiral symmetry breaking even in the free theory. I present results for meson masses, the chiral condensate and fermionic eigenvalues from simulations of quenched QCD on random lattices in four dimensions, focusing on chiral symmetry breaking.
Fast Fits for Lattice QCD Correlators
K. Hornbostel; G. P. Lepage; C. T. H. Davies; R. J. Dowdall; H. Na; J. Shigemitsu
2011-11-06T23:59:59.000Z
We illustrate a technique for fitting lattice QCD correlators to sums of exponentials that is significantly faster than traditional fitting methods --- 10--40 times faster for the realistic examples we present. Our examples are drawn from a recent analysis of the Upsilon spectrum, and another recent analysis of the D -> pi semileptonic form factor. For single correlators, we show how to simplify traditional effective-mass analyses.
B production at the LHC / QCD aspects
Valery P. Andreev
2007-06-12T23:59:59.000Z
The LHC provides new opportunities to improve our understanding of the b quark using high statistics data samples and the 14 TeV center-of-mass energy. The prospects to measure the cross section for inclusive b production in events containing jets and at least one muon are presented. Studies of detector systematic effects and theoretical uncertainties are included. QCD aspects of the beauty production are discussed.
Dual superconducting properties of the QCD vacuum
A. D'Alessandro; M. D'Elia
2005-10-27T23:59:59.000Z
A consistent description of the confining QCD vacuum as a dual superconductor requires a determination of fundamental parameters such as the superconductor correlation length $\\xi$ and the field penetration depth $\\lambda$, which determine whether the superconductor is of type I or type II. We illustrate preliminary results of a lattice determination of $\\xi$ for the case of pure Yang-Mills with two colors, obtained by measuring the temporal correlator of a disorder parameter detecting dual superconductivity.
The Effective Action for QCD at High Energies
Lech Szymanowski
1994-11-16T23:59:59.000Z
I discuss the construction of the effective action for QCD suitable for the description of high-energy and small momentum transfer diffractive processes.
Light Baryons from 2+1 flavor DWF QCD
C. M. Maynard; RBC; UKQCD collaborations
2010-01-28T23:59:59.000Z
We present results from the RBC and UKQCD collaboration ensembles of 2+1 flavor DWF QCD for the light baryon spectrum.
Self-consistent Gaussian model of nonperturbative QCD vacuum
A. P. Bakulev; A. V. Pimikov
2006-10-05T23:59:59.000Z
We show that the minimal Gaussian model of nonlocal vacuum quark and quark-gluon condensates in QCD generates the non-transversity of vector current correlators. We suggest the improved Gaussian model of the nonperturbative QCD vacuum, which respects QCD equations of motion and minimizes the revealed gauge-invariance breakdown. We obtain the refined values of pion distribution amplitude (DA) conformal moments using the improved QCD vacuum model and construct the allowed region for Gegenbauer coefficients a_2 and a_4 of the pion DA.
Log-normal distribution for correlators in lattice QCD?
Thomas DeGrand
2012-04-20T23:59:59.000Z
Many hadronic correlators used in spectroscopy calculations in lattice QCD simulations appear to show a log-normal distribution at intermediate time separations.
Thermodynamics of strong-interaction matter from Lattice QCD
Heng-Tong Ding; Frithjof Karsch; Swagato Mukherjee
2015-04-21T23:59:59.000Z
We review results from lattice QCD calculations on the thermodynamics of strong-interaction matter with emphasis on input these calculations can provide to the exploration of the phase diagram and properties of hot and dense matter created in heavy ion experiments. This review is organized as follows: 1) Introduction, 2) QCD thermodynamics on the lattice, 3) QCD phase diagram at high temperature, 4) Bulk thermodynamics, 5) Fluctuations of conserved charges, 6) Transport properties, 7) Open heavy flavors and heavy quarkonia, 8) QCD in external magnetic fields, 9) Summary.
The Color-Flavor Transformation and Lattice QCD
B. Schlittgen; T. Wettig
2002-09-09T23:59:59.000Z
We present the color-flavor transformation for gauge group SU(N_c) and discuss its application to lattice QCD.
QCD and High Energy Interactions: Moriond 2014 Theory Summary
Thomas Gehrmann
2014-06-20T23:59:59.000Z
This article summarizes new theoretical developments, ideas and results that were presented at the 2014 Moriond "QCD and High Energy Interactions".
Quantum Chaos and Quantum Algorithms
Daniel Braun
2001-10-05T23:59:59.000Z
It was recently shown (quant-ph/9909074) that parasitic random interactions between the qubits in a quantum computer can induce quantum chaos and put into question the operability of a quantum computer. In this work I investigate whether already the interactions between the qubits introduced with the intention to operate the quantum computer may lead to quantum chaos. The analysis focuses on two well--known quantum algorithms, namely Grover's search algorithm and the quantum Fourier transform. I show that in both cases the same very unusual combination of signatures from chaotic and from integrable dynamics arises.
Michele Mosca
2008-08-04T23:59:59.000Z
This article surveys the state of the art in quantum computer algorithms, including both black-box and non-black-box results. It is infeasible to detail all the known quantum algorithms, so a representative sample is given. This includes a summary of the early quantum algorithms, a description of the Abelian Hidden Subgroup algorithms (including Shor's factoring and discrete logarithm algorithms), quantum searching and amplitude amplification, quantum algorithms for simulating quantum mechanical systems, several non-trivial generalizations of the Abelian Hidden Subgroup Problem (and related techniques), the quantum walk paradigm for quantum algorithms, the paradigm of adiabatic algorithms, a family of ``topological'' algorithms, and algorithms for quantum tasks which cannot be done by a classical computer, followed by a discussion.
Multiplicity Distributions in QCD at Very High Energies
I. M. Dremin
1994-08-18T23:59:59.000Z
Recent results in QCD on multiplicity distributions are briefly reviewed. QCD is able to predict very tiny features of multiplicity distributions which demonstrate that the negative binomial distribution (and, more generally, any infinitely divisible distribution) is inappropriate for precise description of experimental data. New fits of high energy multiplicity distributions can be derived.
Static-light meson masses from twisted mass lattice QCD
Static-light meson masses from twisted mass lattice QCD Karl Jansen, Chris Michael, Andrea Shindler of Groningen. · Spain: University of Valencia. · Switzerland: University of Bern. Marc Wagner, "Static-light meson masses from twisted mass lattice QCD", July 16, 2008 #12;Introduction · Static-light meson
The CKM matrix and flavor physics from lattice QCD
Ruth S. Van de Water
2009-11-16T23:59:59.000Z
I discuss the role of lattice QCD in testing the Standard Model and searching for physics beyond the Standard Model in the quark flavor sector. I first review the Standard Model CKM framework. I then present the current status of the CKM matrix, focusing on determinations of CKM matrix elements and constraints on the CKM unitarity triangle that rely on lattice QCD calculations of weak matrix elements. I also show the potential impact of improved lattice QCD calculations on the global CKM unitarity triangle fit. I then describe several hints of new physics in the quark flavor sector that rely on lattice QCD calculations of weak matrix elements, such as evidence of a ~2-3 sigma tension in the CKM unitarity triangle and the "f_{D_s} puzzle". I finish with a discussion of lattice QCD calculations of rare B- and K-decays needed to probe physics beyond the Standard Model at future experiments.
Ronnie Kosloff
2013-05-10T23:59:59.000Z
Quantum thermodynamics addresses the emergence of thermodynamical laws from quantum mechanics. The link is based on the intimate connection of quantum thermodynamics with the theory of open quantum systems. Quantum mechanics inserts dynamics into thermodynamics giving a sound foundation to finite-time-thermodynamics. The emergence of the 0-law I-law II-law and III-law of thermodynamics from quantum considerations is presented. The emphasis is on consistence between the two theories which address the same subject from different foundations. We claim that inconsistency is the result of faulty analysis pointing to flaws in approximations.
Neutrinoless double beta decay and QCD corrections
Namit Mahajan
2014-01-30T23:59:59.000Z
We consider one loop QCD corrections and renormalization group running of the neutrinoless double beta decay amplitude focusing on the short-range part of the amplitude (without the light neutrino exchange) and find that these corrections can be sizeable. Depending on the operator under consideration, there can be moderate to large cancellations or significant enhancements. We discuss several specific examples in this context. Such large corrections will lead to significant shifts in the half-life estimates which currently are known to be plagued with the uncertainties due to nuclear physics inputs to the physical matrix elements.
QCD on GPUs: cost effective supercomputing
M. A. Clark
2009-12-20T23:59:59.000Z
The exponential growth of floating point power in graphics processing units (GPUs), together with their low cost, has given rise to an attractive platform upon which to deploy lattice QCD calculations. GPUs are essentially many (O(100)) core chips, that are programmed using a massively threaded environment, and so are representative of the future of high performance computing (HPC). The large ratio of raw floating point operations per second to memory bandwidth that is characteristic of GPUs necessitates that unique algorithmic design choices are made to harness their full potential. We review the progress to date in using GPUs for large scale calculations, and contrast GPUs against more traditional HPC architectures
Finite Temperature Lattice QCD with Clover Fermions
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
1996-07-31T23:59:59.000Z
We report on our simulation of finite temperature lattice QCD with two flavors of ${\\cal O}(a)$ Symanzik-improved fermions and ${\\cal O}(a^2)$ Symanzik-improved glue. Our thermodynamic simulations were performed on an $8^3 \\times 4$ lattice, and we have performed complementary zero temperature simulations on an $8^3 \\times 16$ lattice. We compare our results to those from simulations with two flavors of Wilson fermions and discuss the improvement resulting from use of the improved action.
The QCD collisional energy loss revised
A. Peshier
2006-05-29T23:59:59.000Z
It is shown that to leading order the QCD collisional energy loss reads $dE/dx \\sim \\alpha(m_D^2)T^2$. Compared to prevalent expressions, $dE^B/dx \\sim \\alpha^2 T^2 \\ln(ET/m_D^2)$, which could be considered adaptions of the (QED) Bethe-Bloch formula, the rectified result takes into account the running coupling, as dictated by renormalization. As one significant consequence, due to asymptotic freedom, the collisional energy loss becomes independent of the jet energy $E$. Some implications with regard to heavy ion collisions are pointed out.
Resummed QCD Power Corrections to Nuclear Shadowing
Qiu, J; Qiu, Jianwei; Vitev, Ivan
2004-01-01T23:59:59.000Z
We calculate and resum a perturbative expansion of nuclear enhanced power corrections to the structure functions measured in deeply inelastic scattering of leptons on a nuclear target. Our results for the Bjorken $x$-, $Q^2$- and $A$-dependence of nuclear shadowing in $F_2^A(x,Q^2)$ and the nuclear modifications to $F_L^A(x,Q^2)$, obtained in terms of the QCD factorization approach, are consistent with the existing data. We demonstrate that the low-$Q^2$ behavior of these data and the measured large longitudinal structure function point to a critical role for the power corrections when compared to other theoretical approaches.
Resummed QCD Power Corrections to Nuclear Shadowing
Jianwei Qiu; Ivan Vitev
2005-01-10T23:59:59.000Z
We calculate and resum a perturbative expansion of nuclear enhanced power corrections to the structure functions measured in deeply inelastic scattering of leptons on a nuclear target. Our results for the Bjorken $x$-, $Q^2$- and $A$-dependence of nuclear shadowing in $F_2^A(x,Q^2)$ and the nuclear modifications to $F_L^A(x,Q^2)$, obtained in terms of the QCD factorization approach, are consistent with the existing data. We demonstrate that the low-$Q^2$ behavior of these data and the measured large longitudinal structure function point to a critical role for the power corrections when compared to other theoretical approaches.
On QCD Thermodynamics with Improved Actions
Karsch, Frithjof
1998-01-01T23:59:59.000Z
We discuss recent advances in the calculation of thermodynamic observables using improved actions. In particular, we discuss the calculation of the equation of state of the SU(3) gauge theory, the critical temperature in units of the string tension, the surface tension and the latent heat at the deconfinement transition. We also present first results from a calculation of the equation of state for four-flavour QCD using an O(a^2) improved staggered fermion action and discuss possible further improvements of the staggered fermion action.
Bottomonium above Deconfinement in Lattice Nonrelativistic QCD
Aarts, G. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Kim, S. [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, M. P. [INFN-Laboratori Nazionali de Frascati, I-00044, Frascati (RM) Italy (Italy); Oktay, M. B. [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112-0830 (United States); Ryan, S. M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Sinclair, D. K. [HEP Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Skullerud, J.-I. [Department of Mathematical Physics, National University of Ireland Maynooth, Maynooth, County Kildare (Ireland)
2011-02-11T23:59:59.000Z
We study the temperature dependence of bottomonium for temperatures in the range 0.4T{sub c}
Bottomonium above deconfinement in lattice nonrelativistic QCD.
Aarts, G.; Lombardo, M. P.; Oktay, M. B.; Ryan, S. M.; Sinclair, D. K.; Skullerud, J.-I.; High Energy Physics; Swansea Univ.; Sejong Univ.; INFN, Frascati; Univ. of Utah; Trinity Coll.; National Univ. of Ireland Maynooth
2011-02-11T23:59:59.000Z
We study the temperature dependence of bottomonium for temperatures in the range 0.4T{sub c} < T < 2.1T{sub c}, using nonrelativistic dynamics for the bottom quark and full relativistic lattice QCD simulations for N{sub f} = 2 light flavors on a highly anisotropic lattice. We find that the Y is insensitive to the temperature in this range, while the x{sub b} propagators show a crossover from the exponential decay characterizing the hadronic phase to a power-law behavior consistent with nearly free dynamics at T {approx} 2T{sub c}.
The renormalization group and lattice QCD
Gupta, R.
1989-01-01T23:59:59.000Z
This report discusses the following topics: scaling of thermodynamic quantities and critical exponents; scaling relations; block spin idea of Kadanoff; exact RG solution of the 1-d Ising model; Wilson's formulation of the renormalization group; linearized transformation matrix and classification of exponents; derivation of exponents from the eigenvalues of {Tau}{sub {alpha}{beta}}; simple field theory: the gaussian model; linear renormalization group transformations; numerical methods: MCRG; block transformations for 4-d SU(N) LGT; asymptotic freedom makes QCD simple; non-perturbative {beta}-function and scaling; and the holy grail: the renormalized trajectory.
None
2011-10-06T23:59:59.000Z
Modern QCD - Lecture 5 We will introduce and discuss in some detail the two main classes of jets: cone type and sequential-recombination type. We will discuss their basic properties, as well as more advanced concepts such as jet substructure, jet filtering, ways of optimizing the jet radius, ways of defining the areas of jets, and of establishing the quality measure of the jet-algorithm in terms of discriminating power in specific searches. Finally we will discuss applications for Higgs searches involving boosted particles.
The QCD vacuum probed by overlap fermions
V. Weinberg; E. -M. Ilgenfritz; K. Koller; Y. Koma; G. Schierholz; T. Streuer
2006-10-13T23:59:59.000Z
We summarize different uses of the eigenmodes of the Neuberger overlap operator for the analysis of the QCD vacuum, here applied to quenched configurations simulated by means of the Luescher-Weisz action. We describe the localization and chiral properties of the lowest modes. The overlap-based topological charge density (with and without UV-filtering) is compared with the results of UV-filtering for the field strength tensor. The latter allows to identify domains of good (anti-)selfduality. All these techniques together lead to a dual picture of the vacuum, unifying the infrared instanton picture with the presence of singular defects co-existent at different scales.
Pion electric polarizability from lattice QCD
Andrei Alexandru; Michael Lujan; Walter Freeman; Frank Lee
2015-01-26T23:59:59.000Z
Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New experiments at CERN and Jefferson Lab are planned that will measure the polarizabilities more precisely. Lattice QCD can be used to compute these quantities directly in terms of quark and gluons degrees of freedom, using the background field method. We present results for the electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in polarizability studies.
Unraveling the organization of the QCD tapestry
J. Papavassiliou
2015-03-13T23:59:59.000Z
I review some key aspects of the ongoing progress in our understanding of the infrared dynamics of the QCD Green's functions, derived from the close synergy between Schwinger-Dyson equations and lattice simulations. Particular attention is dedicated to the elaborate nonperturbative mechanisms that endow the fundamental degrees of freedom (quarks and gluons) with dynamical masses. In addition, the recently established connection between the effective interaction obtained from the gauge sector of the theory and that needed for the veracious description of the ground-state properties of hadrons is briefly presented.
Unraveling the organization of the QCD tapestry
Papavassiliou, J
2015-01-01T23:59:59.000Z
I review some key aspects of the ongoing progress in our understanding of the infrared dynamics of the QCD Green's functions, derived from the close synergy between Schwinger-Dyson equations and lattice simulations. Particular attention is dedicated to the elaborate nonperturbative mechanisms that endow the fundamental degrees of freedom (quarks and gluons) with dynamical masses. In addition, the recently established connection between the effective interaction obtained from the gauge sector of the theory and that needed for the veracious description of the ground-state properties of hadrons is briefly presented.
Quantum correlations; quantum probability approach
W. A. Majewski
2015-05-21T23:59:59.000Z
This survey gives a comprehensive account of quantum correlations understood as a phenomenon stemming from the rules of quantization. Centered on quantum probability it describes the physical concepts related to correlations (both classical and quantum), mathematical structures, and their consequences. These include the canonical form of classical correlation functionals, general definitions of separable (entangled) states, definition and analysis of quantumness of correlations, description of entanglement of formation, and PPT states. This work is intended both for physicists interested not only in collection of results but also in the mathematical methods justifying them, and mathematicians looking for an application of quantum probability to concrete new problems of quantum theory.
AdS/QCD and Applications of Light-Front Holography
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; Cao, Fu-Guang; /Massey U.; de Teramond, Guy F.; /Costa Rica U.
2012-02-16T23:59:59.000Z
Light-Front Holography leads to a rigorous connection between hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space and frame-independent light-front wavefunctions of hadrons in 3 + 1 physical space-time, thus providing a compelling physical interpretation of the AdS/CFT correspondence principle and AdS/QCD, a useful framework which describes the correspondence between theories in a modified AdS5 background and confining field theories in physical space-time. To a first semiclassical approximation, where quantum loops and quark masses are not included, this approach leads to a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time. The internal structure of hadrons is explicitly introduced and the angular momentum of the constituents plays a key role. We give an overview of the light-front holographic approach to strongly coupled QCD. In particular, we study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The results for the TFFs for the {eta} and {eta}' mesons are also presented. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.
QCD evolution in the fully unintegrated form
S. Jadach; M. Skrzypek
2009-05-09T23:59:59.000Z
The next-to-leading order (NLO) evolution of the parton distribution functions (PDF's) in QCD is the "industry standard" in the lepton-hadron and hadron-hadron collider data analysis. The standard NLO DGLAP evolution is formulated for inclusive (integrated) PDFs and is done using inclusive NLO kernels. We report here on the ongoing project, called KRKMC, in which NLO DGLAP evolution is performed for the exclusive multiparton (fully unintegrated) distributions (ePDF's) with the help of the exclusive kernels. These kernels are calculated within the two-parton phase space for bremsstrahlung subset of the Feynman diagrams of the non-singlet evolution, using Curci-Furmanski-Petronzio factorization scheme. The multiparton distribution with multiple use of the exclusive NLO kernels is implemented in the Monte Carlo program simulating multi-gluon emission from single quark emitter. With high statistics tests ($\\sim 10^{9}$ events) it is shown that the new scheme works perfectly well in practice and is equivalent at the inclusive level with the traditional inclusive NLO DGLAP evolution. Once completed, this Monte Carlo module is aimed as a building block for the NLO parton shower Monte Carlo, for W/Z production at LHC and for ep scattering, as well as a starting point for other perturbative QCD based Monte Carlo projects.
Charmed bottom baryon spectroscopy from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Brown, Zachary S; Detmold, William; Meinel, Stefan; Orginos, Kostas
2014-11-01T23:59:59.000Z
We calculate the masses of baryons containing one, two, or three heavy quarks using lattice QCD. We consider all possible combinations of charm and bottom quarks, and compute a total of 36 different states with JP = 1/2+ and JP = 3/2+. We use domain-wall fermions for the up, down, and strange quarks, a relativistic heavy-quark action for the charm quarks, and nonrelativistic QCD for the bottom quarks. Our analysis includes results from two different lattice spacings and seven different pion masses. We perform extrapolations of the baryon masses to the continuum limit and to the physical pion mass using SU(4|2) heavy-hadron chiral perturbation theory including 1/mQ and finite-volume effects. For the 14 singly heavy baryons that have already been observed, our results agree with the experimental values within the uncertainties. We compare our predictions for the hitherto unobserved states with other lattice calculations and quark-model studies.
Spin-Orbit Force from Lattice QCD
K. Murano; N. Ishii; S. Aoki; T. Doi; T. Hatsuda; Y. Ikeda; T. Inoue; H. Nemura; K. Sasaki
2014-06-19T23:59:59.000Z
We present a first attempt to determine nucleon-nucleon potentials in the parity-odd sector, which appear in 1P1, 3P0, 3P1, 3P2-3F2 channels, in Nf=2 lattice QCD simulations. These potentials are constructed from the Nambu-Bethe-Salpeter wave functions for J^P=0^-, 1^- and 2^-, which correspond to A1^-, T1^- and T2^- + E^- representation of the cubic group, respectively. We have found a large and attractive spin-orbit potential VLS(r) in the isospin-triplet channel, which is qualitatively consistent with the phenomenological determination from the experimental scattering phase shifts. The potentials obtained from lattice QCD are used to calculate the scattering phase shifts in 1P1, 3P0, 3P1 and 3P2-3F2 channels. The strong attractive spin-orbit force and a weak repulsive central force in spin-triplet P-wave channels lead to an attraction in the 3P2 channel, which is related to the P-wave neutron paring in neutron stars.
Lattice QCD input for axion cosmology
Berkowitz, Evan; Rinaldi, Enrico
2015-01-01T23:59:59.000Z
One intriguing BSM particle is the QCD axion, which could simultaneously provide a solution to the Strong CP problem and account for some, if not all, of the dark matter density in the universe. This particle is a pNGB of the conjectured Peccei-Quinn (PQ) symmetry of the Standard Model. Its mass and interactions are suppressed by a heavy symmetry breaking scale, $f_a$, whose value is roughly greater than $10^{9}$ GeV (or, conversely, the axion mass, $m_a$, is roughly less than $10^4\\ \\mu \\text{eV}$). The density of axions in the universe, which cannot exceed the relic dark matter density and is a quantity of great interest in axion experiments like ADMX, is a result of the early-universe interplay between cosmological evolution and the axion mass as a function of temperature. The latter quantity is proportional to the second derivative of the QCD free energy with respect to the CP-violating phase, $\\theta$. However, this quantity is generically non-perturbative and previous calculations have only employed ins...
Charmed bottom baryon spectroscopy from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Brown, Zachary S.; Detmold, William; Meinel, Stefan; Orginos, Kostas
2014-11-01T23:59:59.000Z
We calculate the masses of baryons containing one, two, or three heavy quarks using lattice QCD. We consider all possible combinations of charm and bottom quarks, and compute a total of 36 different states with JP = 1/2+ and JP = 3/2+. We use domain-wall fermions for the up, down, and strange quarks, a relativistic heavy-quark action for the charm quarks, and nonrelativistic QCD for the bottom quarks. Our analysis includes results from two different lattice spacings and seven different pion masses. We perform extrapolations of the baryon masses to the continuum limit and to the physical pion mass usingmore »SU(4|2) heavy-hadron chiral perturbation theory including 1/mQ and finite-volume effects. For the 14 singly heavy baryons that have already been observed, our results agree with the experimental values within the uncertainties. We compare our predictions for the hitherto unobserved states with other lattice calculations and quark-model studies.« less
Nicolas Gisin
2015-07-18T23:59:59.000Z
Quantum Communication is the art of transferring an unknown quantum state from one location, Alice, to a distant one, Bob. This is a non-trivial task because of the quantum no-cloning theorem which prevents one from merely using only classical means.
QCD strings and the thermodynamics of the metastable phase of QCD at large $N_c$
Thomas D. Cohen
2006-09-27T23:59:59.000Z
The thermodyanmics of a metastable hadronic phase of QCD at large $N_C$ are related to properties of an effective QCD string. In particular, it is shown that in the large $N_c$ limit and near the maximum hadronic temperature, $T_H$, the energy density and pressure of the metastable phase scale as ${\\cal E} \\sim (T_H-T)^{-(D_\\perp-6)/2}$ (for $D_\\perp <6$) and $P \\sim (T_H-T)^{-(D_\\perp-4)/2}$ (for $D_\\perp <4$) where $D_\\perp$ is the effective number of transverse dimensions of the string theory. It is shown, however, that for the thermodynamic quantities of interest the limits $T \\to T_H$ and $N_c \\to \\infty$ do not commute. The prospect of extracting $D_\\perp$ via lattice simulations of the metastable hadronic phase at moderately large $N_c$ is discussed.
Shepelyansky, Dima
Applications of quantum chaos to realistic quantum computations and sound treatment on quantum speech and sound of complex quantum wavefunctions. Keywords: Quantum computers, quantum chaos
Improving the Infra-red of Holographic Descriptions of QCD
Nick Evans; Andrew Tedder; Tom Waterson
2007-01-03T23:59:59.000Z
A surprisingly good holographic description of QCD can be obtained from naive five dimensional gauge theory on a truncated AdS space. We seek to improve the infra-red description of QCD in such models by using a more sophisticated metric and an action derived from string theory duals of chiral symmetry breaking. Our metric is smooth into the infra-red and the chiral condensate is a prediction of the dynamics. The theory reproduces QCD meson data at the 10% level.
Handbook Article on Applications of Random Matrix Theory to QCD
J. J. M. Verbaarschot
2009-10-21T23:59:59.000Z
In this chapter of the Oxford Handbook of Random Matrix Theory we introduce chiral Random Matrix Theories with the global symmetries of QCD. In the microscopic domain, these theories reproduce the mass and chemical potential dependence of QCD. The main focus of this chapter is on the spectral properties of the QCD Dirac operator and relations between chiral Random Matrix Theories and chiral Lagrangians. Both spectra of the anti-hermitian Dirac operator and spectra of the nonhermitian Dirac operator at nonzero chemical potential are discussed.
Axionic dark energy and a composite QCD axion
Kim, Jihn E. [Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747 (Korea, Republic of)] [Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747 (Korea, Republic of); Nilles, Hans Peter, E-mail: jekim@ctp.snu.ac.kr, E-mail: nilles@th.physik.uni-bonn.de [Bethe Center for Theoretical Physics and Physikalisches Institut, Universitaet Bonn, D-53115, Bonn (Germany)
2009-05-15T23:59:59.000Z
We discuss the idea that the model-independent (MI) axion of string theory is the source of quintessential dark energy. The scenario is completed with a composite QCD axion from hidden sector squark condensation that could serve as dark matter candidate. The mechanism relies on the fact that the hidden sector anomaly contribution to the composite axion is much smaller than the QCD anomaly term. This intuitively surprising scenario is based on the fact that below the hidden sector scale {Lambda}{sub h} there are many light hidden sector quarks. Simply, by counting engineering dimensions the hidden sector instanton potential can be made negligible compared to the QCD anomaly term.
Albert Schwarz
2014-08-16T23:59:59.000Z
One says that a pair (P,Q) of ordinary differential operators specify a quantum curve if [P,Q]=const. If a pair of difference operators (K,L) obey the relation KL=const LK we say that they specify a discrete quantum curve. This terminology is prompted by well known results about commuting differential and difference operators, relating pairs of such operators with pairs of meromorphic functions on algebraic curves obeying some conditions. The goal of this paper is to study the moduli spaces of quantum curves. We will show how to quantize a pair of commuting differential or difference operators (i.e. to construct the corresponding quantum curve or discrete quantum curve). The KP-hierarchy acts on the moduli space of quantum curves; we prove that similarly the discrete KP-hierarchy acts on the moduli space of discrete quantum curves.
Lattice QCD input for axion cosmology
Evan Berkowitz; Michael I. Buchoff; Enrico Rinaldi
2015-05-27T23:59:59.000Z
One intriguing BSM particle is the QCD axion, which could simultaneously provide a solution to the Strong CP problem and account for some, if not all, of the dark matter density in the universe. This particle is a pNGB of the conjectured Peccei-Quinn (PQ) symmetry of the Standard Model. Its mass and interactions are suppressed by a heavy symmetry breaking scale, $f_a$, whose value is roughly greater than $10^{9}$ GeV (or, conversely, the axion mass, $m_a$, is roughly less than $10^4\\ \\mu \\text{eV}$). The density of axions in the universe, which cannot exceed the relic dark matter density and is a quantity of great interest in axion experiments like ADMX, is a result of the early-universe interplay between cosmological evolution and the axion mass as a function of temperature. The latter quantity is proportional to the second derivative of the QCD free energy with respect to the CP-violating phase, $\\theta$. However, this quantity is generically non-perturbative and previous calculations have only employed instanton models at the high temperatures of interest (roughly 1 GeV). In this and future works, we aim to calculate the temperature-dependent axion mass at small $\\theta$ from first-principle lattice calculations, with controlled statistical and systematic errors. Once calculated, this temperature-dependent axion mass is input for the classical evolution equations of the axion density of the universe. Due to a variety of lattice systematic effects at the very high temperatures required, we perform a calculation of the leading small-$\\theta$ cumulant of the theta vacua on large volume lattices for SU(3) Yang-Mills with high statistics as a first proof of concept, before attempting a full QCD calculation in the future. From these pure glue results, the misalignment mechanism yields the axion mass bound $m_a \\geq (14.6\\pm0.1) \\ \\mu \\text{eV}$ when PQ-breaking occurs after inflation.
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.
Quantum information science and complex quantum systems
Michael A. Nielsen
2002-10-01T23:59:59.000Z
What makes quantum information science a science? This paper explores the idea that quantum information science may offer a powerful approach to the study of complex quantum systems.
Dense QCD: a Holographic Dyonic Salt
Mannque Rho; Sang-Jin Sin; Ismail Zahed
2009-10-23T23:59:59.000Z
Dense QCD at zero temperature with a large number of colors is a crystal. We show that in the holographic dual description, the crystal is made out of pairs of dyons with $e=g=\\pm 1$ charges in a salt-like arrangement. We argue that with increasing density the dyon masses and topological charges equalize, turning the salt-like configuration to a bcc of half-instantons. The latter is dual to a cubic crystal of half-skyrmions. We estimate the transition from an fcc crystal of instantons to a bcc crystal of dyons to about 3 times nuclear matter density with a dyon binding energy of about 180 MeV.
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.
Nucleon Axial Form Factor from Lattice QCD
Liu, K F; Draper, T; Wu, J M; Wilcox, W
1994-01-01T23:59:59.000Z
Results for the isovector axial form factors of the proton from a lattice QCD calculation are presented for both point-split and local currents. They are obtained on a quenched $16^{3} \\times 24$ lattice at $\\beta= 6.0$ with Wilson fermions for a range of quark masses from strange to charm. We determine the finite lattice renormalization for both the local and point-split currents of heavy quarks. Results extrapolated to the chiral limit show that the $q^2$ dependence of the axial form factor agrees reasonably well with experiment. The axial coupling constant $g_A$ calculated for the local and the point-split currents is about 6\\% and 12\\% smaller than the experimental value respectively.
New formalism for QCD parton showers.
Gieseke, Stefan; Stephens, Phil; Webber, Bryan R
light quark we define as in sect. 5.1 qi = ?ipa + ?in+ q?i (5.32) – 22 – for i = a, c, g, where q?a = 0, q?c = ?k?, q?g = k?, and n is as in eq. (5.3). Then the ?i’s and ?i’s are given by eqs. (5.7) with the substitution b ? a. The light antiquark... generator. Keywords: QCD, Jets, Heavy Quark Physics. Contents 1. Introduction 2 2. New variables for parton branching 3 2.1 Final-state quark branching 3 2.1.1 Kinematics 3 2.1.2 Running coupling 3 2.1.3 Evolution variable 4 2.1.4 Branching probability 4 2.2...
The QCD phase diagram from analytic continuation
Bellwied, R; Fodor, Z; Günther, J; Katz, S D; Ratti, C; Szabo, K K
2015-01-01T23:59:59.000Z
We present the crossover line between the quark gluon plasma and the hadron gas phases for small real chemical potentials. First we determine the effect of imaginary values of the chemical potential on the transition temperature using lattice QCD simulations. Then we use various formulas to perform an analytic continuation to real values of the baryo-chemical potential. Our data set maintains strangeness neutrality to match the conditions of heavy ion physics. The systematic errors are under control up to $\\mu_B\\approx 300$ MeV. For the curvature of the transition line we find that there is an approximate agreement between values from three different observables: the chiral susceptibility, chiral condensate and strange quark susceptibility. The continuum extrapolation is based on $N_t=$ 10, 12 and 16 lattices. By combining the analysis for these three observables we find, for the curvature, the value $\\kappa = 0.0149 \\pm 0.0021$.
Axel Maas; Daniel Zwanziger
2013-01-15T23:59:59.000Z
We derive some exact bounds on the free energy $W(J)$ in QCD, where $J_\\mu^b$ is a source for the gluon field $A_\\mu^b$ in the minimal Landau gauge, and $W(J)$ is the generating functional of connected gluon correlators. Among other results, we show that for a static source $J(x) = h$ the free energy vanishes, $W(h) = 0$, together with its first derivative, ${\\partial W(h) \\over \\partial h} = 0,$ for all $h$, no matter how strong. Thus the system does not respond to a static color probe. We also present numerical evaluations of the free energy $W(J)$ and find that the bounds are well satisfied and in fact undersaturated.
QCD Breaks Lorentz Invariance and Colour
Balachandran, A P
2015-01-01T23:59:59.000Z
In a previous work [1], we have argued that the algebra of non-abelian superselection rules is spontaneously broken to its maximal abelian subalgebra, that is, the algebra generated by its completing commuting set (the two Casimirs and a basis of its Cartan subalgebra). In this paper, alternative arguments confirming these results are presented. In addition, Lorentz invariance is shown to be broken in QCD, just as it is in QED. The experimental consequences of these results include fuzzy mass and spin shells of coloured particles like quarks, and decay life times which depend on the frame of observation [2, 4]. In a paper under preparation, these results are extended to the ADM Poincare' group and the local Lorentz group of frames. The renormalisation of the ADM energy by infrared gravitons is also estimated.
Helium Nuclei in Quenched Lattice QCD
T. Yamazaki; Y. Kuramashi; A. Ukawa; for the PACS-CS Collaboration
2009-12-08T23:59:59.000Z
We present results for the binding energies for He and ^3He nuclei calculated in quenched lattice QCD at the lattice spacing of a = 0.128 fm with a heavy quark mass corresponding to m_pi = 0.8 GeV. Enormous computational cost for the nucleus correlation functions is reduced by avoiding redundancy of equivalent contractions stemming from permutation symmetry of protons or neutrons in the nucleus and various other symmetries. To distinguish a bound state from an attractive scattering state, we investigate the volume dependence of the energy difference between the nucleus and the free multi-nucleon states by changing the spatial extent of the lattice from 3.1 fm to 12.3 fm. A finite energy difference left in the infinite spatial volume limit leads to the conclusion that the measured ground states are bounded. It is also encouraging that the measured binding energies and the experimental ones show the same order of magnitude.
Recent progress in lattice QCD at finite temperature
Peter Petreczky
2009-06-02T23:59:59.000Z
I review recent progress in finite temperature lattice calculations, including the study of the nature of the deconfinement transition in QCD, equation of state, screening of static quarks and meson spectral functions.
Unsafe but calculable: ratios of angularities in perturbative QCD
Thaler, Jesse
Infrared- and collinear-safe (IRC-safe) observables have finite cross sections to each fixed-order in perturbative QCD. Generically, ratios of IRC-safe observables are themselves not IRC safe and do not have a valid ...
QCD Multipole Expansion and Hadronic Transitions in Heavy Quarkonium Systems
Yu-Ping Kuang
2006-01-18T23:59:59.000Z
We review the developments of QCD multipole expansion and its applications to hadronic transitions and some radiative decays of heavy quarkonia. Theoretical predictions are compsred with updated experimental results.
Neutral pion lifetime measurements and the QCD chiral anomaly
Bernstein, Aron M.
A fundamental property of QCD is the presence of the chiral anomaly, which is the dominant component of the ?[superscript 0]??? decay rate. Based on this anomaly and its small (?4.5%) chiral correction, a prediction of the ...
Debye mass at the QCD transition in the PNJL model
Jankowski, J; Kaczmarek, O
2015-01-01T23:59:59.000Z
We consider colour-electric screening as expressed by the quark contribution to the Debye mass calculated in a PNJL model with emphasis on confining and chiral symmetry breaking effects. We observe that the screening mass is entirely determined by the nonperturbative quark distribution function and temperature dependent QCD running coupling. The role of the gluon background (Polyakov loop) is to provide strong suppression of the number of charge carriers below the transition temperature, as an effect of confinement, while the temperature dependent dynamical quark mass contributes additional suppression, as an effect of chiral symmetry breaking. An alternative derivation of this result from a modified kinetic theory is given, which allows for a slight generalization and explicit contact with perturbative QCD. This gives the possibility to gain insights into the colour screening mechanism in the region near the QCD pseudocritical temperature and to provide a guideline for the interpretation of lattice QCD data.
QCD and High Energy Interactions: Moriond 2015 Theory Summary
Zanderighi, Giulia
2015-01-01T23:59:59.000Z
I will summarise the new theory developments that emerged during the 2015 QCD Moriond conference. I will give my perspective on some of the topics and emphasise what I consider most relevant.
QCD effects in Higgs boson production at hadron colliders
M. Grazzini
2010-01-21T23:59:59.000Z
We present updated predictions for Higgs boson production at the Tevatron and the LHC and we review their corresponding uncertainties. We report on a study of the impact of QCD radiative corrections on the Higgs boson search at the Tevatron.
Non-perturbative QCD amplitudes in quenched and eikonal approximations
Fried, H.M. [Physics Department, Brown University, Providence, RI 02912 (United States); Grandou, T., E-mail: Thierry.Grandou@inln.cnrs.fr [Université de Nice-Sophia Antipolis, Institut Non Linéaire de Nice, UMR 6618 CNRS 7335, 1361 routes des Lucioles, 06560 Valbonne (France); Sheu, Y.-M., E-mail: ymsheu@alumni.brown.edu [Université de Nice-Sophia Antipolis, Institut Non Linéaire de Nice, UMR 6618 CNRS 7335, 1361 routes des Lucioles, 06560 Valbonne (France)
2014-05-15T23:59:59.000Z
Even though approximated, strong coupling non-perturbative QCD amplitudes remain very difficult to obtain. In this article, in eikonal and quenched approximations at least, physical insights are presented that rely on the newly-discovered property of effective locality. The present article also provides a more rigorous mathematical basis for the crude approximations used in the previous derivation of the binding potential of quarks and nucleons. Furthermore, the techniques of Random Matrix calculus along with Meijer G-functions are applied to analyze the generic structure of fermionic amplitudes in QCD. - Highlights: • We discuss the physical insight of effective locality to QCD fermionic amplitudes. • We show that an unavoidable delta function goes along with the effective locality property. • The generic structure of QCD fermion amplitudes is obtained through Random Matrix calculus.
Strongly coupled plasmas and the QCD critical point
Athanasiou, Christiana
2011-01-01T23:59:59.000Z
In this thesis, we begin by studying selected fluctuation observables in order to locate the QCD critical point in heavy-ion collision experiments. In particular, we look at the non-monotonic behavior as a function of the ...
QCD results at HERAQ Aspen 2008 Winter Conference
QCD results at HERAQ Aspen 2008 Winter Conference "Revealing the Nature of Electroweak Symmetry Breaking" 14 January 2008, Aspen, CO, USA Yuji Yamazaki (Kobe University, ZEUS) O b h lf f th H1 d ZEUS ll
A New Mass Formula for NG Bosons in QCD
Reginald T. Cahill; Susan M. Gunner
1995-09-01T23:59:59.000Z
An often used mass formula for Nambu-Goldstone (NG) bosons in QCD, such as the pions, involves the condensate $$, $f_{\\pi}$ and the quark current masses. We argue, within the context of the Global Colour Model to QCD, that this expression is wrong. Analysis of the interplay between the Dyson-Schwinger equation for the constituent quark effect and the Bethe-Salpeter equation for the NG boson results in a new mass formula.
Evolution of gravitational waves through the cosmological QCD transition
Dominik J. Schwarz
1998-11-06T23:59:59.000Z
The spectrum of gravitational waves that have been produced in inflation is modified during cosmological transitions. Large drops in the number of relativistic particles, like during the QCD transition or at $e^+e^-$ annihilation, lead to steps in the spectrum of gravitational waves. We calculate the transfer function for the differential energy density of gravitational waves for a first-order and for a crossover QCD transition.
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.
Buried treasure in the sand of the QCD vacuum
P. J. Moran; D. B. Leinweber
2008-05-28T23:59:59.000Z
The short-range structure of the 2+1 flavour QCD vacuum is studied through visualisations of the topological charge density. Of particular interest is a new Gaussian weighted smearing algorithm which is applied to the rough topological charge density to disclose underlying long range structure. The results provide support for the view of the QCD vacuum as a sandwich of sign-alternating sheets of charge, with a long-range structure hidden beneath.
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 sum rules for the baryon octet in nuclear matter
E. L. Kryshen
2011-08-01T23:59:59.000Z
The baryon self-energies are expressed in terms of the QCD condensates of the lowest dimension in symmetric and asymmetric nuclear matter within the QCD sum-rule approach. The self-energies are shown to satisfy the Gell-Mann--Okubo relations in the linear SU(3) breaking approximation. The results are in qualitative agreement with those obtained by the standard nuclear physics methods.
Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena
Brodsky, Stanley J.; /SLAC /Southern Denmark U., CP3-Origins; de Teramond, Guy F.; /Costa Rica U.
2012-02-16T23:59:59.000Z
Light-Front Holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations it provides important physical insights into the nonperturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics - a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions {Psi}{sub n/H} (x{sub i}, k{sub {perpendicular}i}, {lambda}{sub i}) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and transverse momentum distributions. The effective confining potential also creates quark-antiquark pairs from the amplitude q {yields} q{bar q}q. Thus in holographic QCD higher Fock states can have any number of extra q{bar q} pairs. We discuss the relevance of higher Fock-states for describing the detailed structure of space and time-like form factors. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also obtained.
Khan, Shabbir A
2013-01-01T23:59:59.000Z
Quantum plasma physics is a rapidly evolving research field with a very inter-disciplinary scope of potential applications, ranging from nano-scale science in condensed matter to the vast scales of astrophysical objects. The theoretical description of quantum plasmas relies on various approaches, microscopic or macroscopic, some of which have obvious relation to classical plasma models. The appropriate model should, in principle, incorporate the quantum mechanical effects such as diffraction, spin statistics and correlations, operative on the relevant scales. However, first-principle approaches such as quantum Monte Carlo and density functional theory or quantum-statistical methods such as quantum kinetic theory or non-equilibrium Green's functions require substantial theoretical and computational efforts. Therefore, for selected problems, alternative simpler methods have been put forward. In particular, the collective behavior of many-body systems is usually described within a self-consistent scheme of parti...
R. Tsekov
2012-12-05T23:59:59.000Z
The Brownian motion of a light quantum particle in a heavy classical gas is theoretically described and a new expression for the friction coefficient is obtained for arbitrary temperature. At zero temperature it equals to the de Broglie momentum of the mean free path divided by the mean free path. Alternatively, the corresponding mobility of the quantum particle in the classical gas is equal to the square of the mean free path divided by the Planck constant. The Brownian motion of a quantum particle in a quantum environment is also discussed.
Inevitability and Importance of Non-Perturbative Elements in Quantum Field Theory
Alexander P. Bakulev; Dmitry V. Shirkov
2011-02-11T23:59:59.000Z
The subject of the first section-lecture is concerned with the strength and the weakness of the perturbation theory (PT) approach, that is expansion in powers of a small parameter $\\alpha$, in Quantum Theory. We start with outlining a general troublesome feature of the main quantum theory instrument, the perturbation expansion method. The striking issue is that perturbation series in powers of $\\alpha \\ll 1$ is not a convergent series. The formal reason is an essential singularity of quantum amplitude (matrix element) $C(\\alpha)$ at the origin $\\alpha=0$. In many physically important cases one needs some alternative means of theoretical analysis. In particular, this refers to perturbative QCD (pQCD) in the low-energy domain. In the second section-lecture, we discuss the approach of Analytic Perturbation Theory (APT). We start with a short historic preamble and then discuss how combining the Dispersion Relation with the Renormalization Group (RG) techniques yields the APT with \\myMath{\\displaystyle e^{-1/\\alpha}} nonanalyticity. Next we consider the results of APT applications to low-energy QCD processes and show that in this approach the fourth-loop contributions, which appear to be on the asymptotic border in the pQCD approach, are of the order of a few per mil. Then we note that using the RG in QCD dictates the need to use the Fractional APT (FAPT) and describe its basic ingredients. As an example of the FAPT application in QCD we consider the pion form factor $F_\\pi(Q^2)$ calculation. At the end, we discuss the resummation of nonpower series in {(F)APT} with application to the estimation of the Higgs-boson-decay width $\\Gamma_{H\\to\\bar{b}b}(m_H^2)$.
Quantum Chaos in Compact Lattice QED
B. A. Berg; H. Markum; R. Pullirsch
1998-12-10T23:59:59.000Z
Complete eigenvalue spectra of the staggered Dirac operator in quenched $4d$ compact QED are studied on $8^3 \\times 4$ and $8^3 \\times 6$ lattices. We investigate the behavior of the nearest-neighbor spacing distribution $P(s)$ as a measure of the fluctuation properties of the eigenvalues in the strong coupling and the Coulomb phase. In both phases we find agreement with the Wigner surmise of the unitary ensemble of random-matrix theory indicating quantum chaos. Combining this with previous results on QCD, we conjecture that quite generally the non-linear couplings of quantum field theories lead to a chaotic behavior of the eigenvalues of the Dirac operator.
Quantum chaos in compact lattice QED
Berg, B.A. [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States)] [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States); [Supercomputer Computations Research Institute, The Florida State University, Tallahassee, Florida 32306 (United States); Markum, H. [Institut fuer Kernphysik, Technische Universitaet Wien, A-1040 Vienna (Austria)] [Institut fuer Kernphysik, Technische Universitaet Wien, A-1040 Vienna (Austria); Pullirsch, R. [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States)] [Department of Physics, The Florida State University, Tallahassee, Florida 32306 (United States); [Institut fuer Kernphysik, Technische Universitaet Wien, A-1040 Vienna (Austria)
1999-05-01T23:59:59.000Z
Complete eigenvalue spectra of the staggered Dirac operator in quenched 4D compact QED are studied on 8{sup 3}{times}4 and 8{sup 3}{times}6 lattices. We investigate the behavior of the nearest-neighbor spacing distribution P(s) as a measure of the fluctuation properties of the eigenvalues in the strong coupling and the Coulomb phase. In both phases we find agreement with the Wigner surmise of the unitary ensemble of random-matrix theory indicating quantum chaos. Combining this with previous results on QCD, we conjecture that quite generally the non-linear couplings of quantum field theories lead to a chaotic behavior of the eigenvalues of the Dirac operator. {copyright} {ital 1999} {ital The American Physical Society}
Sai Vinjanampathy; Janet Anders
2015-08-25T23:59:59.000Z
Quantum thermodynamics is an emerging research field aiming to extend standard thermodynamics and non-equilibrium statistical physics to ensembles of sizes well below the thermodynamic limit, in non-equilibrium situations, and with the full inclusion of quantum effects. Fuelled by experimental advances and the potential of future nanoscale applications this research effort is pursued by scientists with different backgrounds, including statistical physics, many-body theory, mesoscopic physics and quantum information theory, who bring various tools and methods to the field. A multitude of theoretical questions are being addressed ranging from issues of thermalisation of quantum systems and various definitions of "work", to the efficiency and power of quantum engines. This overview provides a perspective on a selection of these current trends accessible to postgraduate students and researchers alike.
The (magnetized) effective QCD phase diagram
Alejandro Ayala
2015-09-02T23:59:59.000Z
I present the highlights of a recent study of the effective QCD phase diagram on the temperature T and quark chemical potential mu plane, where the strong interactions are modeled using the linear sigma model coupled to quarks. The phase transition line is found from the effective potential at finite T and mu taking into account the plasma screening effects. We find the location of the critical end point (CEP) to be (mu^CEP/T_c,T^CEP/T_c) \\sim (1.2,0.8), where T_c is the (pseudo)critical temperature for the crossover phase transition at vanishing mu. This location lies within the region found by lattice inspired calculations. Since the linear sigma model does not exhibit confinement, I argue that the location is due to the proper treatment of the plasma screening effects and not to the size of the confining scale. I also comment on the extension of this study to determine the dependence of the CEP's location on the strength of an external magnetic field.
Infrared Freezing of Euclidean QCD observables
Paul M. Brooks; C. J. Maxwell
2006-08-22T23:59:59.000Z
We consider the leading one-chain term in a skeleton expansion for QCD observables and show that for energies Q^2>\\Lambda^2, where Q^2=\\Lambda^2 is the Landau pole in the coupling, the skeleton expansion result is equivalent to the standard Borel integral representation, with ambiguities related to infrared (IR) renormalons. For Q^2freezing behaviour, vanishing at Q^2=0. Finiteness at Q^2=\\Lambda^2 implies specific relations between the residues of IR and UV renormalons in the Borel plane. These relations, only one of which has previously been noted (though it remained unexplained) are shown to follow from the continuity of the characteristic function in the skeleton expansion. By considering the compensation of non-perturbative and perturbative ambiguities we are led to a result for the Q^2 dependence of these observables at all Q^2, in which there is a single undetermined non-perturbative parameter, and which involves the skeleton expansion characteristic function. The observables freeze to zero in the infrared. We briefly consider the freezing behaviour of the Minkowskian R_{e+e-} ratio.
Exact and approximate fermion Green`s functions in QED and QCD
Fried, H.M. [Physics Department, Brown University, Providence, Rhode Island 02912 (United States)] [Physics Department, Brown University, Providence, Rhode Island 02912 (United States); Gabellini, Y. [Institut Non-Lineaire de Nice, 1361, Route des Lucioles, 06560 Valbonne (France)] [Institut Non-Lineaire de Nice, 1361, Route des Lucioles, 06560 Valbonne (France); McKellar, B.H.J. [School of Physics, University of Melbourne, Parkville, Victoria, 3052 (Australia)] [School of Physics, University of Melbourne, Parkville, Victoria, 3052 (Australia)
1995-06-15T23:59:59.000Z
That special variant of the Fradkin representation, previously defined for scalar Green`s functions {ital G}{sub {ital c}}({ital x},{ital y}{vert_bar}{ital A}) in an arbitrary potential {ital A}({ital z}), is here extended to the case of vector interactions and spinor Green`s functions of QED and QCD. An exact representation is given which may again be approximated by a finite number {ital N} of quadratures, with the order of magnitude of the errors generated specified in advance, and decreasing with increasing {ital N}. A feature appears for both exact and approximate {ital G}{sub {ital c}}[{ital A}]: the possibility of chaotic behavior of a function central to the representation, which in turn generates chaotic behavior in {ital G}{sub {ital c}}[{ital A}] for certain {ital A}({ital z}). An example is given to show how the general criterion specified here works for a known case of ``quantum chaos,`` in a potential theory context of first quantization. When the full, nonperturbative, radiative corrections of quantum field theory are included, such chaotic effects are removed.
Higgs-boson production through gluon fusion at NNLO QCD with...
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DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Khachatryan, Vardan
2014-10-14T23:59:59.000Z
Event-shape variables, which are sensitive to perturbative and nonperturbative aspects of quantum chromodynamic (QCD) interactions, are studied in multijet events recorded in proton-proton collisions at s?=7 TeV. Events are selected with at least one jet with transverse momentum p T > 110 GeV and pseudorapidity |?| < 2.4, in a data sample corresponding to integrated luminosities of up to 5 fb?1. The distributions of five event-shape variables in various leading jet p T ranges are compared to predictions from different QCD Monte Carlo event generators.
Marquard, P; Seidel, D; Steinhauser, M
2009-01-01T23:59:59.000Z
We evaluate the corrections to the matching coefficient of the vector current between Quantum Chromodynamics (QCD) and Non-Relativistic QCD (NRQCD) to three-loop order containing a closed heavy-fermion loop. The result constitutes a building block both for the bottom- and top-quark system at threshold. Strong emphasis is put on our completely automated approach of the calculation including the generation of the Feynman diagrams, the identification of the topologies, the reduction to master integrals and the automated numerical computation of the latter.
P. Marquard; J. H. Piclum; D. Seidel; M. Steinhauser
2009-04-06T23:59:59.000Z
We evaluate the corrections to the matching coefficient of the vector current between Quantum Chromodynamics (QCD) and Non-Relativistic QCD (NRQCD) to three-loop order containing a closed heavy-fermion loop. The result constitutes a building block both for the bottom- and top-quark system at threshold. Strong emphasis is put on our completely automated approach of the calculation including the generation of the Feynman diagrams, the identification of the topologies, the reduction to master integrals and the automated numerical computation of the latter.
The 3D structure of the hadrons: recents results and experimental program at Jefferson Lab
Munoz Camacho, Carlos [Institut de Physique Nucleaire, Orsay
2014-04-01T23:59:59.000Z
The understanding of Quantum Chromodynamics (QCD) at large distances still remains one of the main outstanding problems of nuclear physics. Studying the internal structure of hadrons provides a way to probe QCD in the non-perturbative domain and can help us unravel the internal structure of the most elementary blocks of matter. Jefferson Lab (JLab) has already delivered results on how elementary quarks and gluons create nucleon structure and properties. The upgrade of JLab to 12 GeV will allow the full exploration of the valence-quark structure of nucleons and the extraction of real threedimensional pictures. I will present recent results and review the future experimental program at JLab.
Maximum Entropy Analysis of the Spectral Functions in Lattice QCD
M. Asakawa; T. Hatsuda; Y. Nakahara
2001-02-26T23:59:59.000Z
First principle calculation of the QCD spectral functions (SPFs) based on the lattice QCD simulations is reviewed. Special emphasis is placed on the Bayesian inference theory and the Maximum Entropy Method (MEM), which is a useful tool to extract SPFs from the imaginary-time correlation functions numerically obtained by the Monte Carlo method. Three important aspects of MEM are (i) it does not require a priori assumptions or parametrizations of SPFs, (ii) for given data, a unique solution is obtained if it exists, and (iii) the statistical significance of the solution can be quantitatively analyzed. The ability of MEM is explicitly demonstrated by using mock data as well as lattice QCD data. When applied to lattice data, MEM correctly reproduces the low-energy resonances and shows the existence of high-energy continuum in hadronic correlation functions. This opens up various possibilities for studying hadronic properties in QCD beyond the conventional way of analyzing the lattice data. Future problems to be studied by MEM in lattice QCD are also summarized.
Probing QCD with jets, photons and weak bosons at the LHC with ATLAS
Cooper, Ben [University College London, London (United Kingdom); Collaboration: ATLAS Collaboration
2012-10-23T23:59:59.000Z
A summary of ATLAS measurements that probe 'hard' QCD interactions in the protonproton collisions of the LHC are presented.
Frank Steiner
1994-02-07T23:59:59.000Z
A short historical overview is given on the development of our knowledge of complex dynamical systems with special emphasis on ergodicity and chaos, and on the semiclassical quantization of integrable and chaotic systems. The general trace formula is discussed as a sound mathematical basis for the semiclassical quantization of chaos. Two conjectures are presented on the basis of which it is argued that there are unique fluctuation properties in quantum mechanics which are universal and, in a well defined sense, maximally random if the corresponding classical system is strongly chaotic. These properties constitute the quantum mechanical analogue of the phenomenon of chaos in classical mechanics. Thus quantum chaos has been found.
Physicalism versus quantum mechanics
Stapp, Henry P; Theoretical Physics Group; Physics Division
2009-01-01T23:59:59.000Z
Foundations of Quantum Mechanics. (Princeton UniversityMind, Matter, and Quantum Mechanics, (Springer, Berlin & NewMindful Universe: Quantum Mechanics and the Participating
TRANSITION TEMPERATURE IN QCD WITH PHYSICAL LIGHT AND STRANGE QUARK MASSES.
KARSCH, F.
2006-11-14T23:59:59.000Z
We present results from a calculation of the transition temperature in QCD with two light (up, down) and one heavier (strange) quark mass as well as for QCD with three degenerate quark masses. Furthermore, we discuss first results from an ongoing calculation of the QCD equation of state with almost realistic light and strange quark masses.
Search for the pentaquark resonance signature in lattice QCD
B. G. Lasscock; J. Hedditch; D. B. Leinweber; W. Melnitchouk; A. W. Thomas; A. G. Williams; R. D. Young; J. M. Zanotti
2005-03-01T23:59:59.000Z
Claims concerning the possible discovery of the $\\Theta^+$ pentaquark, with minimal quark content $uudd\\bar{s}$, have motivated our comprehensive study into possible pentaquark states using lattice QCD. We review various pentaquark interpolating fields in the literature and create a new candidate ideal for lattice QCD simulations. Using these interpolating fields we attempt to isolate a signal for a five-quark resonance. Calculations are performed using improved actions on a large $20^{3} \\times 40$ lattice in the quenched approximation. The standard lattice resonance signal of increasing attraction between baryon constituents for increasing quark mass is not observed for spin-1/2 pentaquark states. We conclude that evidence supporting the existence of a spin-1/2 pentaquark resonance does not exist in quenched QCD.
On the universal critical behavior in 3-flavor QCD
Dominik Smith; Christian Schmidt
2011-09-30T23:59:59.000Z
We analyze the universal critical behavior at the chiral critical point in QCD with three degenerate quark masses. We confirm that this critical point lies in the universality class of the three dimensional Ising model. The symmetry of the Ising model, which is Z(2), is not directly realized in the QCD Hamiltonian. After making an ansatz for the magnetization- and energy-like operators as linear admixtures of the chiral condensate and the gluonic action, we determine several non-universal mixing and normalization constants. These parameters determine an unambiguous mapping of the critical behavior in QCD to that of the 3d-Ising model. We verify its validity by showing that the thus obtained orderparameter scales in accordance with the magnetic equation of state of the 3d-Ising model.
Probability distribution functions in the finite density lattice QCD
S. Ejiri; Y. Nakagawa; S. Aoki; K. Kanaya; H. Saito; T. Hatsuda; H. Ohno; T. Umeda
2012-12-04T23:59:59.000Z
We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. We try to solve the problems which arise in the numerical study of the finite density QCD, focusing on the probability distribution function (histogram). As a first step, we investigate the quark mass dependence and the chemical potential dependence of the probability distribution function as a function of the Polyakov loop when all quark masses are sufficiently large, and study the properties of the distribution function. The effect from the complex phase of the quark determinant is estimated explicitly. The shape of the distribution function changes with the quark mass and the chemical potential. Through the shape of the distribution, the critical surface which separates the first order transition and crossover regions in the heavy quark region is determined for the 2+1-flavor case.
QCD nature of dark energy at finite temperature: cosmological implications
Azizi, K
2015-01-01T23:59:59.000Z
The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from the late time to the early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras.It is found that this model safely define the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The finite temperature ghost dark energy predictions on the Hubble parameter slightly better fit to observations compared to those of zero temperature.
QCD nature of dark energy at finite temperature: cosmological implications
K. Azizi; N. Katirci
2015-06-23T23:59:59.000Z
The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from the late time to the early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras.It is found that this model safely define the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The finite temperature ghost dark energy predictions on the Hubble parameter slightly better fit to observations compared to those of zero temperature.
Giovannetti, Vittorio
We give a consistent quantum description of time, based on Page and Wootters’s conditional probabilities mechanism, which overcomes the criticisms that were raised against similar previous proposals. In particular we show ...
False Vacuum Decay in QCD within an Effective Lagrangian Approach
Todd Fugleberg
2000-06-19T23:59:59.000Z
In an effective Lagrangian approach to QCD we nonperturbatively calculate an analytic approximation to the decay rate of a false vacuum per unit volume, $\\Gamma/V$. We do so for both zero and high temperature theories. This result is important for the study of the early universe at around the time of the QCD phase transition. It is also important in order to determine the possibility of observing this false vacuum decay at the Relativistic Heavy Ion Collider (RHIC). Previously described dramatic signatures of the decay of false vacuum bubbles would occur in our case as well.
Aspects of the confinement mechanism in Landau gauge QCD
Kai Schwenzer
2008-11-21T23:59:59.000Z
I analyze the IR fixed point structure of Landau gauge QCD. Precisely the fixed point with a strong kinematic singularity of the quark-gluon vertex that proved crucial for the recently proposed confinement mechanism in the quenched approximation is absent in dynamical QCD. Therefore, the IR singularities do not induce asymptotic quark confinement but the long-range interaction is screened by unquenching loops at scales of the order of the quark mass. This provides the prerequisite for a microscopic description of deconfinement and string breaking. The fixed points determine the qualitative form of the heavy quark potential and may be relevant for hot and dense matter.
Electromagnetic triangle anomaly and neutral pion condensation in QCD vacuum
Cao, Gaoqing
2015-01-01T23:59:59.000Z
We study the QCD vacuum structure under the influence of an electromagnetic field with a nonzero second Lorentz invariant $I_2=\\vec{E}\\cdot{\\vec B}$. We show that the presence of $I_2$ can induce neutral pion ($\\pi^0$) condensation in the QCD vacuum through the electromagnetic triangle anomaly. Within the frameworks of chiral perturbation theory at leading small-momenta expansion as well as the Nambu--Jona-Lasinio model at leading $1/N_c$ expansion, we quantify the dependence of the $\\pi^0$ condensate on $I_2$. The stability of the $\\pi^0$-condensed vacuum against the Schwinger charged pair production due to electric field is also discussed.
Nucleon and flavor form factors in AdS/QCD
Chakrabarti, Dipankar
2013-01-01T23:59:59.000Z
The electromagnetic form factors for the nucleons are related with the GPDs by sum rules. Using the sum rules we calculate the valence GPDs for $u$ and $d$ quarks in a quark model using the lightfront wavefunctions for the nucleons obtained from AdS/QCD. The flavor decompositions of the nucleon form factors are also calculated from the GPDs in this model. We show that the nucleon form factors and their flavor decompositions calculated in AdS/QCD are in agreement with experimental data.
A computational system for lattice QCD with overlap Dirac quarks
Ting-Wai Chiu; Tung-Han Hsieh; Chao-Hsi Huang; Tsung-Ren Huang
2002-10-31T23:59:59.000Z
We outline the essential features of a Linux PC cluster which is now being developed at National Taiwan University, and discuss how to optimize its hardware and software for lattice QCD with overlap Dirac quarks. At present, the cluster constitutes of 30 nodes, with each node consisting of one Pentium 4 processor (1.6/2.0 GHz), one Gbyte of PC800 RDRAM, one 40/80 Gbyte hard disk, and a network card. The speed of this system is estimated to be 30 Gflops, and its price/performance ratio is better than $1.0/Mflops for 64-bit (double precision) computations in quenched lattice QCD with overlap Dirac quarks.
Nuclear Energy Density Functionals Constrained by Low-Energy QCD
Dario Vretenar
2008-02-06T23:59:59.000Z
A microscopic framework of nuclear energy density functionals is reviewed, which establishes a direct relation between low-energy QCD and nuclear structure, synthesizing effective field theory methods and principles of density functional theory. Guided by two closely related features of QCD in the low-energy limit: a) in-medium changes of vacuum condensates, and b) spontaneous breaking of chiral symmetry; a relativistic energy density functional is developed and applied in studies of ground-state properties of spherical and deformed nuclei.
The Jacobi Polynomials QCD analysis for the polarized structure function
S. Atashbar Tehrani; Ali N. Khorramian
2007-07-31T23:59:59.000Z
We present the results of our QCD analysis for polarized quark distribution and structure function $xg_1 (x,Q^2)$. We use very recently experimental data to parameterize our model. New parameterizations are derived for the quark and gluon distributions for the kinematic range $x \\epsilon [10^{-8},1]$, $Q^2 \\epsilon [1,10^6]$ GeV^2. The analysis is based on the Jacobi polynomials expansion of the polarized structure functions. Our calculations for polarized parton distribution functions based on the Jacobi polynomials method are in good agreement with the other theoretical models. The values of $\\Lambda_{QCD}$ and $\\alpha_s(M_z)$ are determined.
Multi-hadron states in Lattice QCD spectroscopy
Foley, J.; Morningstar, C.; Wong, C. H. [Dept. of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Bulava, J. [NIC, DESY, Platanenallee 6, 15738 Zeuthen (Germany); Juge, K. J. [Dept. of Physics, University of the Pacific, Stockton, CA 95211 (United States); Peardon, M. [School of Mathematics, Trinity College, Dublin 2 (Ireland)
2010-08-05T23:59:59.000Z
The ability to reliably measure the energy of an excited hadron in Lattice QCD simulations hinges on the accurate determination of all lower-lying energies in the same symmetry channel. These include not only single-particle energies, but also the energies of multi-hadron states. This talk deals with the determination of multi-hadron energies in Lattice QCD. The group-theoretical derivation of lattice interpolating operators that couple optimally to multi-hadron states is described. We briefly discuss recent algorithmic developments which allow for the efficient implementation of these operators in software, and present numerical results from the Hadron Spectrum Collaboration.
Bulk viscosity of QCD matter near the critical temperature
D. Kharzeev; K. Tuchin
2007-05-29T23:59:59.000Z
Kubo's formula relates bulk viscosity to the retarded Green's function of the trace of the energy-momentum tensor. Using low energy theorems of QCD for the latter we derive the formula which relates the bulk viscosity to the energy density and pressure of hot matter. We then employ the available lattice QCD data to extract the bulk viscosity as a function of temperature. We find that close to the deconfinement temperature bulk viscosity becomes large, with viscosity-to-entropy ratio zeta/s about 1.
New confining force solution of QCD axion domain wall problem
S. M. Barr; Jihn E. Kim
2014-11-13T23:59:59.000Z
The serious cosmological problems created by the axion-string/axion-domain-wall system in standard axion models are alleviated by positing the existence of a new confining force. The instantons of this force can generate an axion potential that erases the axion strings long before QCD effects become important, thus preventing QCD-generated axion walls from ever appearing. Axion walls generated by the new confining force would decay so early as not to contribute significantly to the energy in axion dark matter.
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.
Correlation functions of hadron currents in the QCD vacuum calculated in lattice QCD
Chu, M. (W.K. Kellogg Radiation Laboratory, California Institute of Technology, 106-38 Pasadena, California 91125 (United States)); Grandy, J.M. (T-8 Group, MS B-285, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)); Huang, S. (Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States)); Negele, J.W. (Center for Theoretical Physics, Laboratory for Nuclear Science Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States))
1993-10-01T23:59:59.000Z
Point-to-point vacuum correlation functions for spatially separated hadron currents are calculated in quenched lattice QCD on a 16[sup 3][times]24 lattice with 6/[ital g][sup 2]=5.7. The lattice data are analyzed in terms of dispersion relations, which enable us to extract physical information from small distances where asymptotic freedom is apparent to large distances where the hadronic resonances dominate. In the pseudoscalar, vector, and axial vector channels where experimental data or phenomenological information are available, semiquantitative agreement is obtained. In the nucleon and [Delta] channels, where no experimental data exist, our lattice data complement experiments. Comparison with approximations based on sum rules and interacting instantons are made, and technical details of the lattice calculation are described.
Auxiliary field Monte-Carlo simulation of strong coupling lattice QCD for QCD phase diagram
Terukazu Ichihara; Akira Ohnishi; Takashi Z. Nakano
2014-10-07T23:59:59.000Z
We study the QCD phase diagram in the strong coupling limit with fluctuation effects by using the auxiliary field Monte-Carlo method. We apply the chiral angle fixing technique in order to obtain finite chiral condensate in the chiral limit in finite volume. The behavior of order parameters suggests that chiral phase transition is the second order or crossover at low chemical potential and the first order at high chemical potential. Compared with the mean field results, the hadronic phase is suppressed at low chemical potential, and is extended at high chemical potential as already suggested in the monomer-dimer-polymer simulations. We find that the sign problem originating from the bosonization procedure is weakened by the phase cancellation mechanism; a complex phase from one site tends to be canceled by the nearest neighbor site phase as long as low momentum auxiliary field contributions dominate.
Sandia Energy - Quantum Optics
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Quantum Optics Home Energy Research EFRCs Solid-State Lighting Science EFRC Quantum Optics Quantum OpticsTara Camacho-Lopez2015-03-30T16:37:03+00:00 Quantum Optics with a Single...
Progress in vacuum susceptibilities and their applications to the chiral phase transition of QCD
Cui, Zhu-Fang; Shi, Yuan-Mei; Wang, Yong-Long; Zong, Hong-Shi
2015-01-01T23:59:59.000Z
The QCD vacuum condensates and various vacuum susceptibilities are all important parameters which characterize the nonperturbative properties of the QCD vacuum. In the QCD sum rules external field formula, various QCD vacuum susceptibilities play important roles in determining the properties of hadrons. In this paper, we review the recent progress in studies of vacuum susceptibilities together with their applications to the chiral phase transition of QCD. The results of the tensor, the vector, the axial-vector, the scalar, and the pseudo-scalar vacuum susceptibilities are shown in detail in the framework of Dyson-Schwinger equations.
Quantum Artificial Intelligence
B. Aoun; M. Tarifi
2011-06-04T23:59:59.000Z
This report introduces researchers in AI to some of the concepts in quantum heurisitics and quantum AI.
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.
Hadron structure from lattice QCD - outlook and future perspectives
Constantia Alexandrou
2014-11-16T23:59:59.000Z
We review results on hadron structure using lattice QCD simulations with pion masses close or at to the physical value. We pay particular attention to recent successes on the computation of the mass of the low-lying baryons and on the challenges involved in evaluating energies of excited states and resonance parameters, as well as, in studies of nucleon structure.
The running coupling of QCD with four flavors
Fatih Tekin; Rainer Sommer; Ulli Wolff
2010-06-03T23:59:59.000Z
We have calculated the step scaling function and the running coupling of QCD in the Schroedinger functional scheme with four flavors of O(a) improved Wilson quarks. Comparisons of our non-perturbative results with 2-loop and 3-loop perturbation theory as well as with non-perturbative data for only two flavors are made.
Complete three-loop QCD corrections to the decay H -> ??
P. Maierhöfer; P. Marquard
2012-12-26T23:59:59.000Z
We present the result for the three-loop singlet QCD corrections to the decay of a Higgs boson into two photons and improve the calculation for the non-singlet case. With the new result presented, the decay width Gamma(H -> \\gamma \\gamma) is completely known at O(G_F \\alpha ^2 \\alpha_s^2, G_F \\alpha ^3).
Static-light meson masses from twisted mass lattice QCD
ETM Collaboration; Karl Jansen; Chris Michael; Andrea Shindler; Marc Wagner
2008-08-15T23:59:59.000Z
We compute the static-light meson spectrum using two-flavor Wilson twisted mass lattice QCD. We have considered five different values for the light quark mass corresponding to 300 MeV < m_PS < 600 MeV. We have extrapolated our results, to make predictions regarding the spectrum of B and B_s mesons.
Review of ATLAS results on MPI, soft QCD and diffraction
Staszewski, Rafal; The ATLAS collaboration
2015-01-01T23:59:59.000Z
The most recent ATLAS measurements on multiple parton interactions, soft QCD and diffraction are presented. The measurements of underlying event in jet and Z bozon events are discussed. Then, the the total cross section measurement with the ALFA detectors is described.
Counting Strings and Phase Transitions in 2D QCD
W. Taylor
1994-05-03T23:59:59.000Z
Several string theories related to QCD in two dimensions are studied. For each of these theories the large $N$ free energy on a (target) sphere of area $A$ is calculated. By considering theories with different subsets of the geometrical structures involved in the full QCD${}_2$ string theory, the different contributions of these structures to the string free energy are calculated using both analytic and numerical methods. The equivalence between the leading terms in the $SU(N)$ and $U(N)$ free energies is simply demonstrated from the string formulation. It is shown that when $\\Omega$-points are removed from the theory, the free energy is convergent for small and large values of $A$ but divergent in an intermediate range. Numerical results indicate that the free energy for the full QCD${}_2$ string fails to converge at the Douglas-Kazakov phase transition point. Similar results for a single chiral sector of the theory, such as has recently been studied by Cordes, Moore, and Ramgoolam, indicate that there are three distinct phases in that theory. These results indicate that from the point of view of the strong coupling phase, the phase transition in the full QCD${}_2$ string arises from the entropy of branch-point singularities.
QCD sum rules and neutron-proton mass difference
Yang, K.; Hwang, W.P. (Department of Physics, National Taiwan University, Taipei, Taiwan 10764 (Taiwan, Province of China)); Henley, E.M. (Department of Physics FM-15, University of Washington, Seattle, Washington 98195 (United States)); Kisslinger, L.S. (Department of Physics, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213 (United States))
1993-04-01T23:59:59.000Z
We use the method of QCD sum rules to investigate the neutron-proton mass difference. We include diagrams consistently up to dimension 9, assuming different [ital up] and [ital down] current-quark masses ([ital m][sub [ital u
Numerical study of perfect wetting in quenched QCD
Brower, R. (Physics Department, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States)); Huang, S. (Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States)); Potvin, J. (Physics Department, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States) Department of Science and Mathematics, Parks College of Saint Louis University, Cahokia, Illinois 62206 (United States)); Rebbi, C.; Ross, J. (Physics Department, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States))
1992-11-15T23:59:59.000Z
In the quenched approximation of QCD, the high-temperature phase (or gluon plasma phase) will be found in one of three degenerate vacua characterized by the average value of the Polyakov loop. Such vacua can coexist separated by a sharp interface. As {ital T}{r arrow}{ital T}{sub {ital c}}{sup +} (the confinement temperature) confined or glueball matter may be able to grow as a layer along this interface. QCD is said to obey {ital perfect} {ital wetting} if these layers are planar, or {ital imperfect} {ital wetting} if they are shaped like lenses. Evidence for perfect wetting in quenched QCD is studied from a calculation of the surface tension {alpha}{sub {ital p},}{ital p}/{ital T}{sup 3} between two high-temperature plasma phases at {ital T}{sub {ital c}} on a 16{sup 2}{times}32{times}4 lattice. By comparison with the value of the surface tension of a hadron-plasma interface, the data suggest that planar slabs or at least very long lenses develop along the interface, implying that QCD obeys perfect wetting.
Improved performance of QCD code on ALiCE
Sroczynski, Z
2003-01-01T23:59:59.000Z
We present results for the performance of QCD code on ALiCE, the Alpha-Linux Cluster Engine at Wuppertal. We describe the techniques employed to optimise the code, including the metaprogramming of assembler kernels, the effects of data layout and an investigation into the overheads incurred by the communication.
Central and tensor Lambda-nucleon potentials from lattice QCD
Nemura, H
2010-01-01T23:59:59.000Z
We present our latest study of Lambda-Nucleon (LN) interaction by using lattice QCD, following up on our report at LATTICE 2008. We have calculated not only the scattering lengths but also the central and tensor potentials, which are obtained from the Bethe-Salpeter (BS) amplitude measured in lattice QCD. For these calculations, we employ two different types of gauge configurations: (i) 2+1 flavor full QCD configurations generated by the PACS-CS collaboration at $\\beta=1.9$ ($a=0.0907(13)$ fm) on a $32^3\\times 64$ lattice, whose spatial volume is (2.90 fm)$^3$, with the quark masses corresponding to $(m_\\pi,m_K)\\approx (301,592)$, $(414,637)$, $(570,724)$ and $(699,787)$ (in units of MeV). (ii) Quenched QCD configurations at $\\beta=5.7$ ($a=0.1416(9)$ fm) on a $32^3\\times48$ lattice, whose spatial volume is (4.5 fm)$^3$, with the quark masses corresponding to $(m_\\pi,m_K)\\approx (512,606)$, $(464, 586)$ and $(407,565)$. The following qualitative features are found: The LN potential has a relatively strong (we...
Singlet Free Energies and Renormalized Polyakov Loop in full QCD
K. Petrov
2006-10-05T23:59:59.000Z
We calculate the free energy of a static quark anti-quark pair and the renormalized Polyakov loop in 2+1- and 3- flavor QCD using $16^3 \\times 4$ and $16^3 \\times 6$ lattices and improved staggered p4 action. We also compare the renormalized Polyakov loop with the results of our earlier studies.
Particle Physics Phenomenology 8. QCD jets and jet algorithms
Sjöstrand, Torbjörn
Particle Physics Phenomenology 8. QCD jets and jet algorithms Torbj¨orn Sj¨ostrand Department: extend Sphericity and Thrust families. Second solution: clustering algorithms, e.g. LUCLUS, JADE, Durham, but in (, ).) Tevatron (Fermilab): cone algorithms, increasingly messy. LHC: return of clustering with new safer
Particle Physics Phenomenology 8. QCD jets and jet algorithms
Sjöstrand, Torbjörn
Particle Physics Phenomenology 8. QCD jets and jet algorithms Torbj¨orn Sj¨ostrand Department Sphericity and Thrust families. Second solution: clustering algorithms, e.g. LUCLUS, JADE, Durham k. All algorithms, increasingly messy. LHC: return of clustering with new safer and faster algorithms. Anti-k "is
Sum Rules and Cutoff Effects in Wilson Lattice QCD
Harvey B. Meyer
2006-09-06T23:59:59.000Z
We use the transfer matrix formalism to derive non-perturbative sum rules in Wilson's lattice QCD with N_f flavours of quarks. The discretization errors on these identities are treated in detail. As an application, it is shown how the sum rules can be exploited to give improved estimates of the continuum spectrum and static potential.
On-Shell Unitarity Bootstrap for QCD Amplitudes
Carola F. Berger; Zvi Bern; Lance J. Dixon; Darren Forde; David A. Kosower
2006-10-16T23:59:59.000Z
We describe the recently developed on-shell bootstrap for computing one-loop amplitudes in non-supersymmetric theories such as QCD. The method combines the unitarity method with loop-level on-shell recursion. The unitarity method is used to compute cut-containing parts of amplitudes, and on-shell recursion is used for the remaining rational terms.
Gauge cooling in complex Langevin for QCD with heavy quarks
Erhard Seiler; Dénes Sexty; Ion-Olimpiu Stamatescu
2012-11-20T23:59:59.000Z
We employ a new method, "gauge cooling", to stabilize complex Langevin simulations of QCD with heavy quarks. The results are checked against results obtained with reweigthing; we find agreement within the estimated errors. The method allows us to go to previously unaccessible high densities.
Alessandro Sergi
2009-07-11T23:59:59.000Z
A critical assessment of the recent developments of molecular biology is presented. The thesis that they do not lead to a conceptual understanding of life and biological systems is defended. Maturana and Varela's concept of autopoiesis is briefly sketched and its logical circularity avoided by postulating the existence of underlying {\\it living processes}, entailing amplification from the microscopic to the macroscopic scale, with increasing complexity in the passage from one scale to the other. Following such a line of thought, the currently accepted model of condensed matter, which is based on electrostatics and short-ranged forces, is criticized. It is suggested that the correct interpretation of quantum dispersion forces (van der Waals, hydrogen bonding, and so on) as quantum coherence effects hints at the necessity of including long-ranged forces (or mechanisms for them) in condensed matter theories of biological processes. Some quantum effects in biology are reviewed and quantum mechanics is acknowledged as conceptually important to biology since without it most (if not all) of the biological structures and signalling processes would not even exist. Moreover, it is suggested that long-range quantum coherent dynamics, including electron polarization, may be invoked to explain signal amplification process in biological systems in general.
Stapp, Henry P
2011-01-01T23:59:59.000Z
Robert Griffiths has recently addressed, within the framework of a 'consistent quantum theory' that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues that the putative proofs of this property that involve hidden variables include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by establishing, instead, properties of a system modified by adding properties alien to the original system. Hence Griffiths' rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence...
Michael Ben-Or; Daniel Gottesman; Avinatan Hassidim
2013-01-09T23:59:59.000Z
We consider fault-tolerant quantum computation in the context where there are no fresh ancilla qubits available during the computation, and where the noise is due to a general quantum channel. We show that there are three classes of noisy channels: In the first, typified by the depolarizing channel, computation is only possible for a logarithmic time. In the second class, of which the dephasing channel is an example, computation is possible for polynomial time. The amplitude damping channel is an example of the third class, and for this class of channels, it is possible to compute for an exponential time in the number of qubits available.
Quantum Holonomies for Quantum Computing
Jiannis Pachos; Paolo Zanardi
2001-03-19T23:59:59.000Z
Holonomic Quantum Computation (HQC) is an all-geometrical approach to quantum information processing. In the HQC strategy information is encoded in degenerate eigen-spaces of a parametric family of Hamiltonians. The computational network of unitary quantum gates is realized by driving adiabatically the Hamiltonian parameters along loops in a control manifold. By properly designing such loops the non-trivial curvature of the underlying bundle geometry gives rise to unitary transformations i.e., holonomies that implement the desired unitary transformations. Conditions necessary for universal QC are stated in terms of the curvature associated to the non-abelian gauge potential (connection) over the control manifold. In view of their geometrical nature the holonomic gates are robust against several kind of perturbations and imperfections. This fact along with the adiabatic fashion in which gates are performed makes in principle HQC an appealing way towards universal fault-tolerant QC.
Quantum Holonomies for Quantum Computing
Pachos, J; Pachos, Jiannis; Zanardi, Paolo
2001-01-01T23:59:59.000Z
Holonomic Quantum Computation (HQC) is an all-geometrical approach to quantum information processing. In the HQC strategy information is encoded in degenerate eigen-spaces of a parametric family of Hamiltonians. The computational network of unitary quantum gates is realized by driving adiabatically the Hamiltonian parameters along loops in a control manifold. By properly designing such loops the non-trivial curvature of the underlying bundle geometry gives rise to unitary transformations i.e., holonomies that implement the desired unitary transformations. Conditions necessary for universal QC are stated in terms of the curvature associated to the non-abelian gauge potential (connection) over the control manifold. In view of their geometrical nature the holonomic gates are robust against several kind of perturbations and imperfections. This fact along with the adiabatic fashion in which gates are performed makes in principle HQC an appealing way towards universal fault-tolerant QC.
Quantum Chaos via the Quantum Action
H. Kröger
2002-12-16T23:59:59.000Z
We discuss the concept of the quantum action with the purpose to characterize and quantitatively compute quantum chaos. As an example we consider in quantum mechanics a 2-D Hamiltonian system - harmonic oscillators with anharmonic coupling - which is classically a chaotic system. We compare Poincar\\'e sections obtained from the quantum action with those from the classical action.
Quantum chaos viewed from quantum action
D. Huard; H. Kröger; G. Melkonyan; L. P. Nadeau; K. J. M. Moriarty
2004-06-18T23:59:59.000Z
We consider a mixed chaotic Hamiltonian system and compare classical with quantum chaos. As alternative to the methods of enegy level spacing statistics and trace formulas, we construct a quantum action and a quantum analogue phase space to analyse quantum chaos.
Quantum arithmetic with the Quantum Fourier Transform
Lidia Ruiz-Perez; Juan Carlos Garcia-Escartin
2014-11-21T23:59:59.000Z
The Quantum Fourier Transform offers an interesting way to perform arithmetic operations on a quantum computer. We review existing Quantum Fourier Transform adders and multipliers and propose some modifications that extend their capabilities. Among the new circuits, we propose a quantum method to compute the weighted average of a series of inputs in the transform domain.
Quantum++ - A C++11 quantum computing library
Vlad Gheorghiu
2014-12-15T23:59:59.000Z
Quantum++ is a general-purpose multi-threaded quantum computing library written in C++11 and composed solely of header files. The library is not restricted to qubit systems or specific quantum information processing tasks, being capable of simulating arbitrary quantum processes. The main design factors taken in consideration were ease of use, portability, and performance.
John Ashmead
2010-05-05T23:59:59.000Z
Normally we quantize along the space dimensions but treat time classically. But from relativity we expect a high level of symmetry between time and space. What happens if we quantize time using the same rules we use to quantize space? To do this, we generalize the paths in the Feynman path integral to include paths that vary in time as well as in space. We use Morlet wavelet decomposition to ensure convergence and normalization of the path integrals. We derive the Schr\\"odinger equation in four dimensions from the short time limit of the path integral expression. We verify that we recover standard quantum theory in the non-relativistic, semi-classical, and long time limits. Quantum time is an experiment factory: most foundational experiments in quantum mechanics can be modified in a way that makes them tests of quantum time. We look at single and double slits in time, scattering by time-varying electric and magnetic fields, and the Aharonov-Bohm effect in time.
Sassoli de Bianchi, Massimiliano, E-mail: autoricerca@gmail.com
2013-09-15T23:59:59.000Z
In a letter to Born, Einstein wrote [42]: “Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the ‘old one.’ I, at any rate, am convinced that He does not throw dice.” In this paper we take seriously Einstein’s famous metaphor, and show that we can gain considerable insight into quantum mechanics by doing something as simple as rolling dice. More precisely, we show how to perform measurements on a single die, to create typical quantum interference effects, and how to connect (entangle) two identical dice, to maximally violate Bell’s inequality. -- Highlights: •Rolling a die is a quantum process admitting a Hilbert space representation. •Rolling experiments with a single die can produce interference effects. •Two connected dice can violate Bell’s inequality. •Correlations need to be created by the measurement, to violate Bell’s inequality.
Quantum Heat Engines Using Superconducting Quantum Circuits
H. T. Quan; Y. D. Wang; Yu-xi Liu; C. P. Sun; Franco Nori
2006-09-14T23:59:59.000Z
We propose a quantum analog of the internal combustion engine used in most cars. Specifically, we study how to implement the Otto-type quantum heat engine (QHE) with the assistance of a Maxwell's demon. Three steps are required: thermalization, quantum measurement, and quantum feedback controlled by the Maxwell demon. We derive the positive-work condition of this composite QHE. Our QHE can be constructed using superconducting quantum circuits. We explicitly demonstrate the essential role of the demon in this macroscopic QHE.
When is a quantum heat engine quantum?
Alexander Friedenberger; Eric Lutz
2015-08-17T23:59:59.000Z
Quantum thermodynamics studies quantum effects in thermal machines. But when is a heat engine, which cyclically interacts with external reservoirs that unavoidably destroy its quantum coherence, really quantum? We here use the Leggett-Garg inequality to assess the nonclassical properties of a single two-level Otto engine. We provide the complete phase diagram characterizing the quantumness of the engine as a function of its parameters and identify three distinct phases. We further derive an explicit expression for the transition temperature.
Spectroscopy of doubly and triply-charmed baryons from lattice QCD
Padmanath, M. [Tata Institute; Edwards, Robert G. [JLAB; Mathur, Nilmani [Tata Institute; Peardon, Michael [Trinity College, Dublin
2013-11-01T23:59:59.000Z
We present the ground and excited state spectra of doubly and triply-charmed baryons by using lattice QCD with dynamical clover fermions. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) ? O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses. Using those splittings for doubly-charmed baryons, and taking input of experimental Bc meson mass, we predict the mass splittings of B?c?Bc to be about 80 ± 8 MeV and m?ccb=8050±10 MeV.
Exact Amplitude-Based Resummation in Quantum Field Theory: Recent Results
Ward, B F L
2012-01-01T23:59:59.000Z
We present the current status of the application of our approach of exact amplitude-based resummation in quantum field theory to two areas of investigation: precision QCD calculations of all three of us as needed for LHC physics and the resummed quantum gravity realization by one of us (B.F.L.W.) of Feynman's formulation of Einstein's theory of general relativity. We discuss recent results as they relate to experimental observations. There is reason for optimism in the attendant comparison of theory and experiment.
Adiabatically implementing quantum gates
Sun, Jie; Lu, Songfeng, E-mail: lusongfeng@hotmail.com; Liu, Fang [School of Computer Science and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)
2014-06-14T23:59:59.000Z
We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.
Testing chiral effective theory with quenched lattice QCD
L. Giusti; P. Hernandez; S. Necco; C. Pena; J. Wennekers; H. Wittig
2008-03-19T23:59:59.000Z
We investigate two-point correlation functions of left-handed currents computed in quenched lattice QCD with the Neuberger-Dirac operator. We consider two lattice spacings a~0.09,0.12 fm and two different lattice extents L~ 1.5, 2.0 fm; quark masses span both the p- and the epsilon-regimes. We compare the results with the predictions of quenched chiral perturbation theory, with the purpose of testing to what extent the effective theory reproduces quenched QCD at low energy. In the p-regime we test volume and quark mass dependence of the pseudoscalar decay constant and mass; in the epsilon-regime, we investigate volume and topology dependence of the correlators. While the leading order behaviour predicted by the effective theory is very well reproduced by the lattice data in the range of parameters that we explored, our numerical data are not precise enough to test next-to-leading order effects.
Heavy hybrid mesons in the QCD sum rule
Peng-Zhi Huang; Shi-Lin Zhu
2015-01-13T23:59:59.000Z
We study the spectra of the hybrid mesons containing one heavy quark ($q\\bar{Q}g$) within the framework of QCD sum rules in the heavy quark limit. The derived sum rules are stable with the variation of the Borel parameter within their corresponding working ranges. The extracted binding energy for the heavy hybrid doublets $H^h(S^h)$ and $M^h(T^h)$ is almost degenerate. We also calculate the pionic couplings between these heavy hybrid and the conventional heavy meson doublets using the light-cone QCD sum rule method. The extracted coupling constants are rather small as a whole. With these couplings we make a rough estimate of the partial widths of these pionic decay channels.
Gauge Configurations for Lattice QCD from The Gauge Connection
DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]
The Gauge Connection is an experimental archive for lattice QCD and a repository of gauge configurations made freely available to the community. Contributors to the archive include the Columbia QCDSP collaboration, the MILC collaboration, and others. Configurations are stored in QCD archive format, consisting of an ASCII header which defines various parameters, followed by binary data. NERSC has also provided some utilities and examples that will aid users in handling the data. Users may browse the archive, but are required to register for a password in order to download data. Contents of the archive are organized under four broad headings: Quenched (more than 1200 configurations); Dynamical, Zero Temperature (more than 300 configurations); MILC Improved Staggered Asqtad Lattices (more than 7000 configurations); and Dynamical, Finite Temperature (more than 1200 configurations)
Baryon Masses in Lattice QCD with Exact Chiral Symmetry
Chiu, T W; Chiu, Ting-Wai; Hsieh, Tung-Han
2005-01-01T23:59:59.000Z
We investigate the baryon mass spectrum in quenched lattice QCD with exact chiral symmetry. For 100 gauge configurations generated with Wilson gauge action at $ \\beta = 6.1 $ on the $ 20^3 \\times 40 $ lattice, we compute (point-to-point) quark propagators for 30 quark masses in the range $ 67 {MeV} \\le m_q \\le 1790 {MeV} $. For baryons only composed of strange and charm quarks, their masses are extracted directly from the time correlation functions, while for those containing $ u (d) $ light quarks, their masses are obtained by chiral extrapolation to $ m_\\pi = 135 $ MeV. Our results of baryon masses are in good agreement with experimental values, except for the negative parity states of $ \\Lambda $ and $ \\Lambda_c $. Further, our results of charmed (including doubly-charmed and triply-charmed) baryons can serve as predictions of QCD.
Report of the 2005 Snowmass Top/QCD Working Group
Juste, A.; /Fermilab; Kiyo, Y.; /Aachen, Tech. Hochsch.; Petriello, F.; /Wisconsin U., Madison /Fermilab; Teubner, T.; /Liverpool U., Dept. Math.; Agashe, K.; Batra, P.; Baur, U.; Berger, C.F.; Cembranos, J.A.R.; Gehrmann-De Ridder, A.; Gehrmann, T.; Glover, E.W.N.; Godfrey, S.; Hoang, A.; Perelstein, M.; Sullivan, Z.; Tait, T.; Zhu, S.; /Johns
2006-01-17T23:59:59.000Z
This report discusses several topics in both top quark physics and QCD at an International Linear Collider (ILC). Issues such as measurements at the t tbar threshold, including both theoretical and machine requirements, and the determination of electroweak top quark couplings are reviewed. New results concerning the potential of a 500 GeV e+e collider for measuring Wtb couplings and the top quark Yukawa coupling are presented. The status of higher order QCD corrections to jet production cross sections, heavy quark form factors, and longitudinal gauge boson scattering, needed for percent-level studies at the ILC, are reviewed. A new study of the measurement of the hadronic structure of the photon at a gamma gamma collider is presented. The effects on top quark properties from several models of new physics, including composite models, Little Higgs theories, and CPT violation, are studied.
More on the renormalization group limit cycle in QCD
Evgeny Epelbaum; Hans-Werner Hammer; Ulf-G. Meissner; Andreas Nogga
2006-02-26T23:59:59.000Z
We present a detailed study of the recently conjectured infrared renormalization group limit cycle in QCD using chiral effective field theory. We show that small increases in the up and down quark masses, corresponding to a pion mass around 200 MeV, can move QCD to the critical renormalization group trajectory for an infrared limit cycle in the three-nucleon system. At the critical values of the quark masses, the binding energies of the deuteron and its spin-singlet partner are tuned to zero and the triton has infinitely many excited states with an accumulation point at the three-nucleon threshold. At next-to-leading order in the chiral counting, we find three parameter sets where this effect occurs. For one of them, we study the structure of the three-nucleon system using both chiral and contact effective field theories in detail. Furthermore, we calculate the influence of the limit cycle on scattering observables.
Neutral Meson Decays into Two Photons from Lattice QCD
Huey-Wen Lin; Saul D. Cohen
2013-02-04T23:59:59.000Z
A precision determination of the neutral-pion width would improve determinations of the splitting between the up- and down-quark masses, and matrix elements for the decay of neutral mesons into two photons could play a role in the attempt to probe beyond-the-Standard Model physics in muon $g-2$ experiments. The theoretical error is dominated by hadronic light-by-light diagrams, and since direct measurements are extremely difficult, model calculations factorize it into two-photon diagrams connected by the lightest hadrons. We employ perturbative techniques to express the photon as a superposition of QCD eigenstates accessible in lattice-QCD calculations and found that vector-meson dominance is a poor description of the two-photon decay process when both photons are off shell.
Poisson statistics in the high temperature QCD Dirac spectrum
Tamás G. Kovács; Ferenc Pittler
2011-11-15T23:59:59.000Z
We analyze the eigenvalue statistics of the staggered Dirac operator above $T_{c}$ in QCD with 2+1 flavors of dynamical quarks. We use physical quark masses in our simulations. We compare the eigenvalue statistics from several parts of the Dirac spectrum with the predictions of Random Matrix Theory for this universality class and with Poisson statistics. We show that at the low end of the spectrum the eigenmodes are localized and obey Poisson statistics. Above a boundary region the eigenmodes become delocalized and obey Random Matrix statistics. Thus the QCD Dirac spectrum with physical dynamical quarks also has the Poisson to Random Matrix transition previously seen in the quenched SU(2) theory.
Inverse magnetic catalysis in holographic models of QCD
Kiminad A. Mamo
2015-05-11T23:59:59.000Z
We study the effect of magnetic field $B$ on the critical temperature $T_{c}$ of the confinement-deconfinement phase transition in hard-wall AdS/QCD, and holographic duals of flavored and unflavored $\\mathcal{N}=4$ super-Yang Mills theories on $\\mathbb{R}^3\\times \\rm S^1$. For all of the holographic models, we find that $T_{c}(B)$ decreases with increasing magnetic field $B\\ll T^2$, consistent with the inverse magnetic catalysis recently observed in lattice QCD for $B\\lesssim 1~GeV^2$. We also predict that, for large magnetic field $B\\gg T^2$, the critical temperature $T_{c}(B)$, eventually, starts to increase with increasing magnetic field $B\\gg T^2$ and asymptotes to a constant value.
QCD and strongly coupled gauge theories: Challenges and perspectives
Brambilla, N. [Technische Univ. Munchen, Garching (Germany); Eidelman, S. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Novosibirsk State Univ., Novosibirsk (Russia); Foka, P. [GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt (Germany); Gardner, S. [Univ. of Kentucky, Lexington, KY (United States); Kronfeld, A. S. [Fermi National Accelerator Laboratory, Batavia, IL (United States); Alford, M. G. [Washington Univ., St. Louis, MO (United States); Alkofer, R. [Univ. of Graz, Graz (Austria); Butenschoen, M. [Univ. of Vienna, Wien (Austria); Cohen, T. D. [Univ. of Maryland, College Park, MD (United States); Erdmenger, J. [Max-Planck-Institute for Physics, Munich (Germany); Fabbietti, L. [Technische Univ. Munchen, Garching (Germany); Faber, M. [Technische Univ. Wien, Vienna (Austria); Goity, J. L. [Hampton Univ., Hampton, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Ketzer, B. [Technische Univ. Munchen, Garching (Germany); Univ. Bonn, Bonn (Germany); Lin, H. W. [Univ. of Washington, Seattle, WA (United States); Llanes-Estrada, F. J. [Univ. Complutense de Madrid, Madrid (Spain); Meyer, H. B. [Johannes Gutenberg Univ., Mainz (Germany); Pakhlov, P. [Institute of Theoretical and Experimental Physics, Moscow (Russia); Moscow Institute for Physics and Technology, Dolgoprudny (Russia); Pallante, E. [Univ. of Groningen, Groningen (The Netherlands); Polikarpov, M. I. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Institute for Physics and Technology, Dolgoprudny (Russian Federation); Sazdjian, H. [Univ. Paris-Sud, Orsay (France); Schmitt, A. [Technische Univ. Wien, Vienna (Austria); Snow, W. M. [Indiana Univ., Bloomington, IN (United States); Vairo, A. [Technische Univ. Munchen, Garching (Germany); Vogt, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Davis, CA (United States); Vuorinen, A. [Univ. of Helsinki, Helsinki (Finland); Wittig, H. [Johannes Gutenberg Univ., Mainz (Germany); Arnold, P. [Univ. of Virginia, Charlottesville, VA (United States); Christakoglou, P. [NIKHEF, Amsterdam (The Netherlands); Di Nezza, P. [Istituto Nazionale di Fisica Nucleare, Frascati (Italy); Fodor, Z. [Wuppertal Univ., Wuppertal (Germany); Eotvos Univ., Budapest (Hungary); Forschungszentrum Julich, Julich (Germany); Garcia i Tormo, X. [Univ. Bern, Bern (Switzerland); Höllwieser, R. [Univ. Wien, Vienna (Austria); Janik, M. A. [Warsaw Univ. of Technology, Warsaw (Poland); Kalweit, A. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Keane, D. [Kent State Univ., Kent, OH (United States); Kiritsis, E. [Univ. of Crete, Heraklion (Greece); Univ. Paris Diderot, Sorbonne Paris-Cite (France); CERN, Geneva (Switzerland); Mischke, A. [Utrecht Univ., Utrecht (The Netherlands); Mizuk, R. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Moscow Physical Engineering Institute, Moscow (Russian Federation); Odyniec, G. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Papadodimas, K. [Univ. of Groningen, Groningen (The Netherlands); Pich, A. [Univ. de Valencia, Valencia (Spain); Pittau, R. [Univ. de Granada, Granada (Spain); Qiu, J. -W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., Stony Brook, NY (United States); Ricciardi, G. [Univ. degli Studi di Napoli Federico II (Italy); INFN, Napoli (Italy); Salgado, C. A. [Univ. de Santiago de Compostela, Galicia (Spain); Schwenzer, K. [Washington Univ., St. Louis, MO (United States); Stefanis, N. G. [Ruhr-Universitat Bochum, Bochum (Germany); von Hippel, G. M. [Johannes Gutenberg Univ., Mainz (Germany); Zakharov, V. I. [Max-Planck-Institute for Physics, Munich (Germany); Institute of Theoretical and Experimental Physics, Moscow (Russia); Moscow Institute for Physics and Technology, Dolgoprudny (Russia); Far Eastern Federal Univ., Vladivostok (Russia)
2014-10-01T23:59:59.000Z
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to stongly-coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.
$??$ interaction from 2+1 flavor lattice QCD
Masanori Yamada; Kenji Sasaki; Sinya Aoki; Takumi Doi; Tetsuo Hatsuda; Yoichi Ikeda; Takashi Inoue; Noriyoshi Ishii; Keiko Murano; Hidekatsu Nemura
2015-03-11T23:59:59.000Z
We investigate the interaction between $\\Omega$ baryons in the $^1S_0$ channel from 2+1 flavor lattice QCD simulations. On the basis of the HAL QCD method, the $\\Omega\\Omega$ potential is extracted from the Nambu-Bethe-Salpeter wave function calculated on the lattice by using the PACS-CS gauge configurations with the lattice spacing $a\\simeq 0.09$ fm, the lattice volume $L\\simeq 2.9$ fm and the quark masses corresponding to $m_\\pi \\simeq 700$ MeV and $m_\\Omega \\simeq 1970$ MeV. The $\\Omega\\Omega$ potential has a repulsive core at short distance and an attractive well at intermediate distance. Accordingly, the phase shift obtained from the potential shows moderate attraction at low energies. Our data indicate that the $\\Omega\\Omega$ system with the present quark masses may appear close to the unitary limit where the scattering length diverges.
String compactification, QCD axion and axion-photon-photon coupling
Kang-Sin Choi; Ian-Woo Kim; Jihn E. Kim
2007-01-13T23:59:59.000Z
It is pointed out that there exist a few problems to be overcome toward an observable sub-eV QCD axion in superstring compactification. We give a general expression for the axion decay constant. For a large domain wall number $N_{DW}$, the axion decay constant can be substantially lowered from a generic value of a scalar singlet VEV. The Yukawa coupling structure in the recent $Z_{12-I}$ model is studied completely, including the needed nonrenormalizable terms toward realistic quark and lepton masses. In this model we find an approximate global symmetry and vacuum so that a QCD axion results but its decay constant is at the GUT scale. The axion-photon-photon coupling is calculated for a realistic vacuum satisfying the quark and lepton mass matrix conditions. It is the first time calculation of $c_{a\\gamma\\gamma}$ in realistic string compactifications: $c_{a\\gamma\\gamma}={5/3}-1.93\\simeq -0.26$.
QCD and strongly coupled gauge theories: Challenges and perspectives
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Brambilla, N.; Eidelman, S.; Foka, P.; Gardner, S.; Kronfeld, A. S.; Alford, M. G.; Alkofer, R.; Butenschoen, M.; Cohen, T. D.; Erdmenger, J.; et al
2014-10-01T23:59:59.000Z
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to stongly-coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many researchmore »streams which flow into and out of QCD, as well as a vision for future developments.« less
Bootstrapping phase transitions in QCD and frustrated spin systems
Yu Nakayama; Tomoki Ohtsuki
2014-08-11T23:59:59.000Z
In view of its physical importance in predicting the order of chiral phase transitions in QCD and frustrated spin systems, we perform the conformal bootstrap program of $O(n)\\times O(2)$-symmetric conformal field theories in $d=3$ dimensions with a special focus on $n=3$ and $4$. The existence of renormalization group fixed points with these symmetries has been controversial over years, but our conformal bootstrap program provides the non-perturbative evidence. In both $n=3$ and $4$ cases, we find singular behaviors in the bounds of scaling dimensions of operators in two different sectors, which we claim correspond to chiral and collinear fixed points, respectively. In contrast to the cases with larger values of $n$, we find no evidence for the anti-chiral fixed point. Our results indicate the possibility that the chiral phase transitions in QCD and frustrated spin systems are continuous with the critical exponents that we predict from the conformal bootstrap program.
QCD tests from pion reactions on few-nucleon systems
C. Hanhart
2010-09-27T23:59:59.000Z
We show on two examples, namely a calculation for charge symmetry breaking in pn->d pi^0 that allows one to extract the quark mass difference induced part of the proton--neutron mass difference and a high precision calculation for pion--deuteron scattering and its implications for the value of the charged pion--nucleon coupling constant, how QCD tests can be performed from low energy hadronic observables.
QCD Jet Rates with the Inclusive Generalized kt Algorithms
Erik Gerwick; Ben Gripaios; Steffen Schumann; Bryan Webber
2013-04-15T23:59:59.000Z
We derive generating functions, valid to next-to-double logarithmic accuracy, for QCD jet rates according to the inclusive forms of the kt, Cambridge/Aachen and anti-kt algorithms, which are equivalent at this level of accuracy. We compare the analytical results with jet rates and average jet multiplicities from the SHERPA event generator, and study the transition between Poisson-like and staircase-like behaviour of jet ratios.
Gauged Nambu-Jona-Lasinio model and axionic QCD string
Chi Xiong
2014-12-30T23:59:59.000Z
We propose an axionic QCD string scenario based on the original flux-tube model by Kogut and Susskind, and then incorporate it into a gauged Nambu-Jona-Lasinio (NJL) model. Axial anomaly is studied by a new topological coupling from the string side, and by the 't Hooft vortex from the NJL side, respectively. The nontrivial phase distribution of the quark condensate plays an important role in this scenario.
Transverse charge and magnetization densities in holographic QCD
Chakrabarti, Dipankar
2014-01-01T23:59:59.000Z
We present a study of flavor structures of nucleons transverse charge and anomalous magnetization densities for both unpolarized and transversely polarized nucleons. We consider two different models for the electromagnetic form factors in holographic QCD. The flavor form factors are obtained by decomposing the Dirac and Pauli form factors for nucleons using the charge and isospin symmetry. The results are compared with two standard phenomenological parametrizations.
Meson structure in light-front holographic QCD
Rohit Swarnkar; Dipankar Chakrabarti
2015-07-06T23:59:59.000Z
We consider the light-front holographic QCD with the light-front wave functions for mesons, modified for massive quarks. We evaluate the wave functions, distribution amplitudes, and form factors for $\\pi$, $\\rho$, $K$, and $J/\\psi$ mesons and photon-to-meson transition form factors for $\\pi$, $\\eta$, and $\\eta^\\prime$. The results are compared with the experimental data, wherever available.
Running Coupling Effects in Small-x QCD
D. N. Triantafyllopoulos
2008-04-11T23:59:59.000Z
We study effects of the running of the coupling in QCD at small Bjorken-x and in particular the ones related to gluon saturation. After introducing the steps taken to the derivation of the next to leading order nonlinear evolution equation, we discuss the infrared sensitivity of the Pomeron intercept, the energy dependence of the saturation momentum and the appearance of geometrical scaling, and the dominance of the running coupling effects over the ones introduced by loops of Pomerons.
Transverse momentum dependent quark densities from Lattice QCD
Bernhard Musch,Philipp Hagler,John Negele,Andreas Schafer
2011-02-01T23:59:59.000Z
We study transverse momentum dependent parton distribution functions (TMDs) with non-local operators in lattice QCD, using MILC/LHPC lattices. Results obtained with a simpli?ed operator geometry show visible dipole de- formations of spin-dependent quark momentum densities. We discuss the basic concepts of the method, including renormalization of the gauge link, and an ex- tension to a more elaborate operator geometry that would allow us to analyze process-dependent TMDs such as the Sivers-function.
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.
Charmonium at high temperature in two-flavor QCD
Aarts, Gert; Allton, Chris [Department of Physics, Swansea University, Singleton Park, Swansea SA2 8PP, Wales (United Kingdom); Oktay, Mehmet Bugrahan; Peardon, Mike; Skullerud, Jon-Ivar [School of Mathematics, Trinity College, Dublin 2 (Ireland)
2007-11-01T23:59:59.000Z
We compute charmonium spectral functions in 2-flavor QCD on anisotropic lattices using the maximum entropy method. Our results suggest that the S-waves (J/{psi} and {eta}{sub c}) survive up to temperatures close to 2T{sub c}, while the P-waves ({chi}{sub c0} and {chi}{sub c1}) melt away below 1.2T{sub c}.
The Additional Interpolators Method for Variational Analysis in Lattice QCD
Rainer W. Schiel
2015-03-09T23:59:59.000Z
In this paper, I describe the Additional Interpolators Method, a new technique for variational analysis in lattice QCD. It is shown to be an excellent method which uses additional interpolators to remove backward in time running states that would otherwise contaminate the signal. The proof of principle, which also makes use of the Time-Shift Trick (Generalized Pencil-of-Functions method), will be delivered at an example on a $64^4$ lattice close to the physical pion mass.
Two-Color QCD with Chiral Chemical Potential
V. V. Braguta; V. A. Goy; E. -M. Ilgenfritz; A. Yu. Kotov; A. V. Molochkov; M. Muller-Preussker; B. Petersson; A. Schreiber
2014-11-19T23:59:59.000Z
The phase diagram of two-color QCD with a chiral chemical potential is studied on the lattice. The focus is on the confinement/deconfinement phase transition and the breaking/restoration of chiral symmetry. The simulations are carried out with dynamical staggered fermions without rooting. The dependence of the Polyakov loop, the chiral condensate and the corresponding susceptibilities on the chiral chemical potential and the temperature are presented.
High-Energy Scattering vs Static QCD Strings
V. A. Petrov; R. A. Ryutin
2014-09-30T23:59:59.000Z
We discuss the shape of the interaction region of the elastically scattered protons stipulated by the high-energy Pomeron exchange which turns out to be very similar with the shape of the static string representing the confining QCD flux tube. This similarity disappears when we enter the LHC energy region, which corresponds to many-Pomeron exchanges. Reversing the argument we conjecture a modified relationship between the width and the length of the confining string at very large lengths.
Top quark physics and QCD: Progress since the TESLA TDR
A. Brandenburg
2003-09-08T23:59:59.000Z
I review progress on investigations concerning top quark physics and QCD at a future linear e+e- collider that has been achieved since the presentation of the TESLA technical design report in spring 2001. I concentrate on studies that have been presented during the workshop series of the Extended Joint ECFA/DESY Study on Physics and Detectors for a Linear Electron-Positron Collider.
Hard two photon processes ??--> M_2 M_1 in QCD
Victor L. Chernyak
2012-12-06T23:59:59.000Z
A short review of leading term QCD predictions vs those of the handbag model for large angle cross sections \\gamma\\gamma --> P_2 P_1 (P is the pseudoscalar meson \\pi^{\\pm,o}, K^{\\pm,o}, \\eta), and for \\gamma\\gamma --> V_2 V_1 (V is the neutral vector meson \\rho^o, \\omega, \\phi), in comparison with Belle Collaboration measuments
Topological Charge and the Laminar Structure of the QCD Vacuum
H. B. Thacker
2006-11-30T23:59:59.000Z
Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based topological charge operator have revealed a laminar structure in the QCD vacuum consisting of extended, thin, coherent, locally 3-dimensional sheets of topological charge embedded in 4D space, with opposite sign sheets interleaved. In this talk I discuss the interpretation of these Monte Carlo results in terms of our current theoretical understanding of theta-dependence and topological structure in asymptotically free gauge theories.
Cosmologically safe QCD axion as a present from extra dimension
Kawasaki, Masahiro; Yanagida, Tsutomu T
2015-01-01T23:59:59.000Z
We propose a QCD axion model where the origin of PQ symmetry and suppression of axion isocurvature perturbations are explained by introducing an extra dimension. Each extra quark-antiquark pair lives on branes separately to suppress PQ breaking operators. The size of the extra dimension changes after inflation due to an interaction between inflaton and a bulk scalar field, which implies that the PQ symmetry can be drastically broken during inflation to suppress undesirable axion isocurvature fluctuations.
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.
Status and prospects for the calculation of hadron structure from lattice QCD
Dru B. Renner
2010-02-04T23:59:59.000Z
Lattice QCD calculations of hadron structure are a valuable complement to many experimental programs as well as an indispensable tool to understand the dynamics of QCD. I present a focused review of a few representative topics chosen to illustrate both the challenges and advances of our community: the momentum fraction, axial charge and charge radius of the nucleon. I will discuss the current status of these calculations and speculate on the prospects for accurate calculations of hadron structure from lattice QCD.
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Stapp, H.P.
1988-04-01T23:59:59.000Z
It is argued that the validity of the predictions of quantum theory in certain spin-correlation experiments entails a violation of Einstein's locality idea that no causal influence can act outside the forward light cone. First, two preliminary arguments suggesting such a violation are reviewed. They both depend, in intermediate stages, on the idea that the results of certain unperformed experiments are physically determinate. The second argument is entangled also with the problem of the meaning of physical reality. A new argument having neither of these characteristics is constructed. It is based strictly on the orthodox ideas of Bohr and Heisenberg, and has no realistic elements, or other ingredients, that are alien to orthodox quantum thinking.
Effective chiral restoration in the hadronic spectrum and QCD
Thomas D. Cohen
2006-05-18T23:59:59.000Z
Effective chiral restoration in the hadronic spectrum has been conjectured as an explanation of multiplets of nearly degenerate seen in highly excited hadrons. The conjecture depends on the states being insensitive to the dynamics of spontaneous chiral symmetry breaking. A key question is whether this concept is well defined in QCD. This paper shows that it is by means of an explicit formal construction. This construction allows one to characterize this sensitivity for any observable calculable in QCD in Euclidean space via a functional integral. The construction depends on a generalization of the Banks-Casher theorem. It exploits the fact that {\\it all} dynamics sensitive to spontaneous chiral symmetry breaking observables in correlation functions arise from fermion modes of zero virtuality (in the infinite volume limit), while such modes make {\\it no} contribution to any of the dynamics which preserves chiral symmetry. In principle this construction can be implemented in lattice QCD. The prospect of a practical lattice implementation yielding a direct numerical test of the concept of effective chiral restoration is discussed.
QCD nature of dark energy at finite temperature: cosmological implications
K. Azizi; N. Katirci
2015-09-20T23:59:59.000Z
The Veneziano ghost field has been proposed as an alternative source of dark energy whose energy density is consistent with the cosmological observations. In this model, the energy density of QCD ghost field is expressed in terms of QCD degrees of freedom at zero temperature. We extend this model to finite temperature to search the model predictions from the late time to the early universe. We depict the variations of QCD parameters entering the calculations, dark energy density, equation of state, Hubble and deceleration parameters on temperature from zero to a critical temperature. We compare our results with the observations and theoretical predictions existing at different eras. It is found that this model safely define the universe from quark condensation up to now and its predictions are not in tension with those of the standard cosmology. The EoS parameter of dark energy is obtained to be $-1/3$ in the presence of radiation and $-1$ at late time. The finite temperature ghost dark energy predictions on the Hubble parameter slightly better fit to observations compared to those of zero temperature.
Matching NLO QCD and parton showers in heavy flavour production
S. Frixione; P. Nason; B. R. Webber
2003-11-04T23:59:59.000Z
We apply the MC@NLO approach to the process of heavy flavour hadroproduction. MC@NLO is a method for matching next-to-leading order (NLO) QCD calculations and parton shower Monte Carlo (MC) simulations, with the following features: fully exclusive events are generated, with hadronisation according to the MC model; total rates are accurate to NLO; NLO results for distributions are recovered upon expansion in $\\as$; hard emissions are treated as in NLO computations while soft/collinear emissions are handled by the MC simulation, with the same logarithmic accuracy as the MC; matching between the hard and soft regions is smooth, and no intermediate integration steps are necessary. The method was applied previously to the hadroproduction of gauge boson pairs, which at NLO involves only initial-state QCD radiation and a unique colour structure. In heavy flavour production, it is necessary to include contributions from final-state QCD radiation and different colour flows. We present illustrative results on top and bottom production at the Tevatron and LHC.
Making QCD Lattice Data Accessible and Organized through Advanced Web Interfaces
Massimo Di Pierro; James Hetrick; Shreyas Cholia; David Skinner
2011-12-09T23:59:59.000Z
The Gauge Connection at qcd.nersc.gov is one of the most popular repositories of QCD lattice ensembles. It is used to access 16TB of archived QCD data from the High Performance Storage System (HPSS) at the National Energy Research Scientific Computing Center (NERSC). Here, we present a new web interface for qcd.nersc.gov which allows physicists to browse and search the data, as well as download individual files or entire ensembles in batch. Our system distinguishes itself from others because of its ease of use and web based workflow.
Physics from the lattice: glueballs in QCD; topology; SU(N) for all N
M. Teper
1997-11-06T23:59:59.000Z
Lectures given at the Isaac Newton Institute, NATO-ASI School on "Confinement, Duality and Non-Perturbative Aspects of QCD", 23 June - 4 July, 1997.
Stapp, Henry
2011-11-10T23:59:59.000Z
Robert Griffiths has recently addressed, within the framework of a ‘consistent quantum theory’ (CQT) that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues, on the basis of his examination of certain arguments that claim to demonstrate the existence of such nonlocal influences, that such influences do not exist. However, his examination was restricted mainly to hidden-variable-based arguments that include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by attributing to the system properties alien to that system. Hence Griffiths’ rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his ‘consistent quantum theory’ shows that the cited proof is valid within that restrictive framework. This necessary existence, within the ‘consistent’ framework, of long range essentially instantaneous influences refutes the claim made by Griffiths that his ‘consistent’ framework is superior to the orthodox quantum theory of von Neumann because it does not entail instantaneous influences. An added section responds to Griffiths’ reply, which cites a litany of ambiguities that seem to restrict, devastatingly, the scope of his CQT formalism, apparently to buttress his claim that my use of that formalism to validate the nonlocality theorem is flawed. But the vagaries that he cites do not upset the proof in question. It is show here in detail why the precise statement of this theorem justifies the specified application of CQT. It is also shown, in response to his challenge, why a putative proof of locality that he has proposed is not valid.
Roumen Tsekov
2011-04-15T23:59:59.000Z
A new approach to thermo-quantum diffusion is proposed and a nonlinear quantum Smoluchowski equation is derived, which describes classical diffusion in the field of the Bohm quantum potential. A nonlinear thermo-quantum expression for the diffusion front is obtained, being a quantum generalization of the classical Einstein law. The quantum diffusion at zero temperature is also described and a new dependence of the position dispersion on time is derived. A stochastic Bohm-Langevin equation is also proposed.
H. J. Kimble
2008-06-25T23:59:59.000Z
Quantum networks offer a unifying set of opportunities and challenges across exciting intellectual and technical frontiers, including for quantum computation, communication, and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for the generation and characterization of quantum coherence and entanglement. Fundamental to this endeavor are quantum interconnects that convert quantum states from one physical system to those of another in a reversible fashion. Such quantum connectivity for networks can be achieved by optical interactions of single photons and atoms, thereby enabling entanglement distribution and quantum teleportation between nodes.
F. Benatti; M. Fannes
1998-11-26T23:59:59.000Z
We use multi-time correlation functions of quantum systems to construct random variables with statistical properties that reflect the degree of complexity of the underlying quantum dynamics.
Quantum Optimal Control Theory
G. H. Gadiyar
1994-05-10T23:59:59.000Z
The possibility of control of phenomena at microscopic level compatible with quantum mechanics and quantum field theory is outlined. The theory could be used in nanotechnology.
Quantum Leap Quantum Mechanics' Killer App
Bigelow, Stephen
Quantum Leap Quantum Mechanics' Killer App Q&A with Craig Hawker Director of the Materials Research. Q&A with Craig Hawker LEAP The Materials Research Laboratory is the only Wes
NMR quantum information processing
Dawei Lu; Aharon Brodutch; Jihyun Park; Hemant Katiyar; Tomas Jochym-O'Connor; Raymond Laflamme
2015-01-07T23:59:59.000Z
Quantum computing exploits fundamentally new models of computation based on quantum mechanical properties instead of classical physics, and it is believed that quantum computers are able to dramatically improve computational power for particular tasks. At present, nuclear magnetic resonance (NMR) has been one of the most successful platforms amongst all current implementations. It has demonstrated universal controls on the largest number of qubits, and many advanced techniques developed in NMR have been adopted to other quantum systems successfully. In this review, we show how NMR quantum processors can satisfy the general requirements of a quantum computer, and describe advanced techniques developed towards this target. Additionally, we review some recent NMR quantum processor experiments. These experiments include benchmarking protocols, quantum error correction, demonstrations of algorithms exploiting quantum properties, exploring the foundations of quantum mechanics, and quantum simulations. Finally we summarize the concepts and comment on future prospects.
Quantum walks and relativistic quantum simulations
Blatt, Rainer
in a quantum simulation of the Klein para- dox. The position and momentum of a relativistic Dirac particle
Next-to-leading order QCD corrections to light Higgs Pair production via vector boson fusion
Terrance Figy
2008-06-15T23:59:59.000Z
We present the NLO QCD corrections for light Higgs pair production via vector boson fusion at the LHC within the CP conserving type II two higgs doublet model in the form of a fully flexible parton--level Monte Carlo program. Scale dependences on integrated cross sections and distributions are reduced with QCD K-factors of order unity.
Niemi, H; Paatelainen, R
2015-01-01T23:59:59.000Z
We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order perturbative QCD using a saturation conjecture to control soft particle production, and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries, against the LHC and RHIC measurements. We compare also the computed event-by-event probability distributions of relative fluctuations of elliptic flow, and event-plane angle correlations, with the experimental data from Pb+Pb collisions at the LHC. We show how such a systematic multi-energy and multi-observable analysis tests the initial state calculation and the applicability region of hydrodynamics, and in particular how ...
Quantum Annealing and Analog Quantum Computation
Arnab Das; Bikas K. Chakrabarti
2008-03-24T23:59:59.000Z
We review here the recent success in quantum annealing, i.e., optimization of the cost or energy functions of complex systems utilizing quantum fluctuations. The concept is introduced in successive steps through the studies of mapping of such computationally hard problems to the classical spin glass problems. The quantum spin glass problems arise with the introduction of quantum fluctuations, and the annealing behavior of the systems as these fluctuations are reduced slowly to zero. This provides a general framework for realizing analog quantum computation.
Localized quantum walks as secured quantum memory
C. M. Chandrashekar; Th. Busch
2015-04-21T23:59:59.000Z
We show that a quantum walk process can be used to construct and secure quantum memory. More precisely, we show that a localized quantum walk with temporal disorder can be engineered to store the information of a single, unknown qubit on a compact position space and faithfully recover it on demand. Since the localization occurss with a finite spread in position space, the stored information of the qubit will be naturally secured from the simple eavesdropper. Our protocol can be adopted to any quantum system for which experimental control over quantum walk dynamics can be achieved.
Quantum cards and quantum rods
Milan Batista; Joze Peternelj
2006-11-02T23:59:59.000Z
Quantum mechanical analysis of a rigid rod with one end fixed to a flat table is presented. It is shown, that for a macroscopic rod the ground state is orientationally delocalized only if the table is absolutely horizontal. In this latter case the rod, assumed to be initally in the upright orientation, falls down symmetrically and simultaneously in both directions, as claimed by Tegmark and Wheeler. In addition, the time of fall is calculated using WKB wavefunctions representing energy eigenstates near the barrier summit.
A Framework for Lattice QCD Calculations on GPUs
Winter, Frank; Clark, M.A.; Edwards, Robert G.; Joo, Balint
2014-08-01T23:59:59.000Z
Computing platforms equipped with accelerators like GPUs have proven to provide great computational power. However, exploiting such platforms for existing scientific applications is not a trivial task. Current GPU programming frameworks such as CUDA C/C++ require low-level programming from the developer in order to achieve high performance code. As a result porting of applications to GPUs is typically limited to time-dominant algorithms and routines, leaving the remainder not accelerated which can open a serious Amdahl's law issue. The lattice QCD application Chroma allows to explore a different porting strategy. The layered structure of the software architecture logically separates the data-parallel from the application layer. The QCD Data-Parallel software layer provides data types and expressions with stencil-like operations suitable for lattice field theory and Chroma implements algorithms in terms of this high-level interface. Thus by porting the low-level layer one can effectively move the whole application in one swing to a different platform. The QDP-JIT/PTX library, the reimplementation of the low-level layer, provides a framework for lattice QCD calculations for the CUDA architecture. The complete software interface is supported and thus applications can be run unaltered on GPU-based parallel computers. This reimplementation was possible due to the availability of a JIT compiler (part of the NVIDIA Linux kernel driver) which translates an assembly-like language (PTX) to GPU code. The expression template technique is used to build PTX code generators and a software cache manages the GPU memory. This reimplementation allows us to deploy an efficient implementation of the full gauge-generation program with dynamical fermions on large-scale GPU-based machines such as Titan and Blue Waters which accelerates the algorithm by more than an order of magnitude.
A Framework for Lattice QCD Calculations on GPUs
F. T. Winter; M. A. Clark; R. G. Edwards; B. Joó
2014-08-25T23:59:59.000Z
Computing platforms equipped with accelerators like GPUs have proven to provide great computational power. However, exploiting such platforms for existing scientific applications is not a trivial task. Current GPU programming frameworks such as CUDA C/C++ require low-level programming from the developer in order to achieve high performance code. As a result porting of applications to GPUs is typically limited to time-dominant algorithms and routines, leaving the remainder not accelerated which can open a serious Amdahl's law issue. The lattice QCD application Chroma allows to explore a different porting strategy. The layered structure of the software architecture logically separates the data-parallel from the application layer. The QCD Data-Parallel software layer provides data types and expressions with stencil-like operations suitable for lattice field theory and Chroma implements algorithms in terms of this high-level interface. Thus by porting the low-level layer one can effectively move the whole application in one swing to a different platform. The QDP-JIT/PTX library, the reimplementation of the low-level layer, provides a framework for lattice QCD calculations for the CUDA architecture. The complete software interface is supported and thus applications can be run unaltered on GPU-based parallel computers. This reimplementation was possible due to the availability of a JIT compiler (part of the NVIDIA Linux kernel driver) which translates an assembly-like language (PTX) to GPU code. The expression template technique is used to build PTX code generators and a software cache manages the GPU memory. This reimplementation allows us to deploy an efficient implementation of the full gauge-generation program with dynamical fermions on large-scale GPU-based machines such as Titan and Blue Waters which accelerates the algorithm by more than an order of magnitude.
Quantum search without entanglement
Lloyd, S
2000-01-01T23:59:59.000Z
Entanglement of quantum variables is usually thought to be a prerequisite for obtaining quantum speed-ups of information processing tasks such as searching databases. This paper presents methods for quantum search that give a speed-up over classical methods, but that do not require entanglement. These methods rely instead on interference to provide a speed-up. Search without entanglement comes at a cost: although they outperform analogous classical devices, the quantum devices that perform the search are not universal quantum computers and require exponentially greater overhead than a quantum computer that operates using entanglement. Quantum search without entanglement is compared to classical search using waves.
Quantum search without entanglement
Seth Lloyd
1999-03-16T23:59:59.000Z
Entanglement of quantum variables is usually thought to be a prerequisite for obtaining quantum speed-ups of information processing tasks such as searching databases. This paper presents methods for quantum search that give a speed-up over classical methods, but that do not require entanglement. These methods rely instead on interference to provide a speed-up. Search without entanglement comes at a cost: although they outperform analogous classical devices, the quantum devices that perform the search are not universal quantum computers and require exponentially greater overhead than a quantum computer that operates using entanglement. Quantum search without entanglement is compared to classical search using waves.
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.
A Modern View of Perturbative QCD and Application to Heavy Quarkonium Systems
Y. Sumino
2014-07-21T23:59:59.000Z
Perturbative QCD has made significant progress over the last few decades. In the first part, we present an introductory overview of perturbative QCD as seen from a modern viewpoint. We explain the relation between purely perturbative predictions and predictions based on Wilsonian effective field theories. We also review progress of modern computational technologies and discuss intersection with frontiers of mathematics. Analyses of singularities in Feynman diagrams play key roles towards developing a unified view. In the second part, we discuss application of perturbative QCD, based on the formulation given in the first part, to heavy quarkonium systems and the interquark force between static color charges. We elucidate impacts on order Lambda_QCD physics in the quark mass and interquark force, which used to be considered inaccessible by perturbative QCD.
Quantum Thermodynamic Cycles and quantum heat engines
H. T. Quan; Yu-xi Liu; C. P. Sun; Franco Nori
2007-04-03T23:59:59.000Z
In order to describe quantum heat engines, here we systematically study isothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum versions of both the Carnot heat engine and the Otto heat engine are defined without ambiguities. We also study the properties of quantum Carnot and Otto heat engines in comparison with their classical counterparts. Relations and mappings between these two quantum heat engines are also investigated by considering their respective quantum thermodynamic processes. In addition, we discuss the role of Maxwell's demon in quantum thermodynamic cycles. We find that there is no violation of the second law, even in the existence of such a demon, when the demon is included correctly as part of the working substance of the heat engine.
Quantum Bootstrapping via Compressed Quantum Hamiltonian Learning
Nathan Wiebe; Christopher Granade; David G. Cory
2015-03-30T23:59:59.000Z
Recent work has shown that quantum simulation is a valuable tool for learning empirical models for quantum systems. We build upon these results by showing that a small quantum simulators can be used to characterize and learn control models for larger devices for wide classes of physically realistic Hamiltonians. This leads to a new application for small quantum computers: characterizing and controlling larger quantum computers. Our protocol achieves this by using Bayesian inference in concert with Lieb-Robinson bounds and interactive quantum learning methods to achieve compressed simulations for characterization. Whereas Fisher information analysis shows that current methods which employ short-time evolution are suboptimal, interactive quantum learning allows us to overcome this limitation. We illustrate the efficiency of our bootstrapping protocol by showing numerically that an 8-qubit Ising model simulator can be used to calibrate and control a 50 qubit Ising simulator while using only about 750 kilobits of experimental data.
Properties of light pseudoscalars from lattice QCD with HISQ ensembles
MILC Collaboration; A. Bazavov; C. Bernard; C. DeTar; W. Freeman; Steven Gottlieb; U. M. Heller; J. E. Hetrick; J. Kim; J. Laiho; L. Levkova; M. Lightman; M. Oktay; J. Osborn; R. L. Sugar; D. Toussaint; R. S. Van de Water
2011-11-18T23:59:59.000Z
We fit lattice-QCD data for light-pseudoscalar masses and decay constants, from HISQ configurations generated by MILC, to SU(3) staggered chiral perturbation theory. At present such fits have rather high values of chi^2/d.o.f., possibly due to the lack of ensembles with lighter-than-physical sea strange-quark masses. We propose solutions to this problem for future work. We also perform simple linear interpolations near the physical point on two ensembles with different lattice spacings, and obtain the preliminary result (f_K / f_pi)^phys = 1.1872(41) in the continuum limit.
The Vacuum Structure of Vector Mesons in QCD
Rennecke, Fabian
2015-01-01T23:59:59.000Z
We study the chiral dynamics of vector mesons in two-flavor QCD in vacuum by utilizing a functional renormalization group approach. This allows us to capture the dynamical transition from the quark-gluon phase at high energies to the hadronic phase at low energies without the necessity of model parameter tuning. We use this to analyze the scaling of vector meson masses towards the chiral symmetry breaking scale, the decoupling of the mesons at high energies and the validity of vector meson dominance.
Spectroscopy of triply charmed baryons from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Padmanath, M; Edwards, Robert G; Mathur, Nilmani; Peardon, Michael
2014-10-01T23:59:59.000Z
The spectrum of excitations of triply-charmed baryons is computed using lattice QCD including dynamical light quark fields. The spectrum obtained has baryonic states with well-defined total spin up to 7/2 and the low-lying states closely resemble the expectation from models with an SU(6)x O(3) symmetry. Energy splittings between extracted states, including those due to spin-orbit coupling in the heavy quark limit are computed and compared against data at other quark masses.
NLO QCD corrections to ZZ jet production at hadron colliders
Binoth, T.; /Edinburgh U.; Gleisberg, T.; /SLAC; Karg, S.; /RWTH Aachen U.; Kauer, N.; /Royal Holloway, U. of London /Southampton U.; Sanguinetti, G.; /Annecy, LAPTH
2010-05-26T23:59:59.000Z
A fully differential calculation of the next-to-leading order QCD corrections to the production of Z-boson pairs in association with a hard jet at the Tevatron and LHC is presented. This process is an important background for Higgs particle and new physics searches at hadron colliders. We find sizable corrections for cross sections and differential distributions, particularly at the LHC. Residual scale uncertainties are typically at the 10% level and can be further reduced by applying a veto against the emission of a second hard jet. Our results confirm that NLO corrections do not simply rescale LO predictions.
The nucleon electromagnetic form factors from Lattice QCD
Alexandrou, C; Negele, J W; Tsapalis, A
2006-01-01T23:59:59.000Z
We evaluate the isovector nucleon electromagnetic form factors in quenched and full QCD on the lattice using Wilson fermions. In the quenched theory we use a lattice of spatial size 3 fm at beta=6.0 enabling us to reach low momentum transfers and a lowest pion mass of about 400 MeV. In the full theory we use a lattice of spatial size 1.9 fm at beta=5.6 and lowest pion mass of about 380 MeV enabling comparison with the results obtained in the quenched theory. We compare our lattice results to the isovector part of the experimentally measured form factors.
Fermionic Quasiparticles in QCD at High Baryon Density
Thomas Schaefer
2005-10-24T23:59:59.000Z
We study fermionic quasi-particles in QCD at very high baryon density. In the normal quark matter phase unscreened magnetic gluon exchanges lead to non-Fermi liquid behavior. Non-Fermi liquid effects manifest themselves in low energy Green functions that depend on logarithms and fractional powers of energy. In the superfluid phase there is an energy gap for fermionic excitations. Quark mass effects can cause the energy gap to vanish. Gapless fermions in the color flavor locked phase cause an instability towards a state with a non-zero supercurrent.
Spectroscopy of triply charmed baryons from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Padmanath, M.; Edwards, Robert G.; Mathur, Nilmani; Peardon, Michael
2014-10-01T23:59:59.000Z
The spectrum of excitations of triply-charmed baryons is computed using lattice QCD including dynamical light quark fields. The spectrum obtained has baryonic states with well-defined total spin up to 7/2 and the low-lying states closely resemble the expectation from models with an SU(6) x O(3) symmetry. Energy splittings between extracted states, including those due to spin-orbit coupling in the heavy quark limit are computed and compared against data at other quark masses.
Electrical conductivity and thermal dilepton rate from quenched lattice QCD
Olaf Kaczmarek; Anthony Francis
2011-09-19T23:59:59.000Z
We report on a continuum extrapolation of the vector current correlation function for light valence quarks in the deconfined phase of quenched QCD. This is achieved by performing a systematic analysis of the influence of cut-off effects on light quark meson correlators at $T\\simeq 1.45 T_c$ using clover improved Wilson fermions. We discuss resulting constraints on the electrical conductivity and the thermal dilepton rate in a quark gluon plasma. In addition new results at 1.2 and 3.0 $T_c$ will be presented.
Elliptic flow from pQCD + saturation + hydro model
K. J. Eskola; H. Niemi; P. V. Ruuskanen
2007-05-15T23:59:59.000Z
We have previously predicted multiplicities and transverse momentum spectra of hadrons for the most central LHC Pb+Pb collisions at $\\sqrt{s_{NN}}=5.5$ TeV using initial state for hydrodynamic evolution from pQCD + final state saturation model. By considering binary collision and wounded nucleon profiles we extend these studies to non-central collisions, and predict the $p_{T}$ dependence of minimum bias $v_{2}$ for pions at the LHC. For protons we also show how the $p_{T}$ dependence of $v_2$ changes from RHIC to the LHC.
An estimate for the location of QCD critical end point
Roy A. Lacey; N. N. Ajitanand; J. M. Alexander; P. Chung; J. Jia; A. Taranenko; P. Danielewicz
2008-05-09T23:59:59.000Z
It is proposed that a study of the ratio of shear viscosity to entropy density $\\frac{\\eta}{s}$ as a function of the baryon chemical potential $\\mu_B$, and temperature T, provides a dynamic probe for the critical end point (CEP) in hot and dense QCD matter. An initial estimate from an elliptic flow excitation function gives $\\mu^{\\text{cep}}_B \\sim 150-180$ MeV and $T_{\\text{cep}} \\sim 165 - 170$ MeV for the location of the the CEP. These values place the CEP in the range for "immediate" validation at RHIC.
Anomalous specific heat in ultradegenerate QED and QCD
A. Gerhold; A. Ipp; A. Rebhan
2004-08-31T23:59:59.000Z
We discuss the origin of the anomalous $T\\ln T^{-1}$ behavior of the low-temperature entropy and specific heat in ultradegenerate QED and QCD and report on a recent calculation which is complete to leading order in the coupling and which contains an infinite series of anomalous terms involving also fractional powers in $T$. This result involves dynamical hard-dense-loop resummation and interpolates between Debye screening effects at larger temperatures and non-Fermi-liquid behavior from only dynamically screened magnetic fields at low temperature.
Anomalous specific heat in high-density QED and QCD
A. Ipp; A. Gerhold; A. Rebhan
2003-09-22T23:59:59.000Z
Long-range quasi-static gauge-boson interactions lead to anomalous (non-Fermi-liquid) behavior of the specific heat in the low-temperature limit of an electron or quark gas with a leading $T\\ln T^{-1}$ term. We obtain perturbative results beyond the leading log approximation and find that dynamical screening gives rise to a low-temperature series involving also anomalous fractional powers $T^{(3+2n)/3}$. We determine their coefficients in perturbation theory up to and including order $T^{7/3}$ and compare with exact numerical results obtained in the large-$N_f$ limit of QED and QCD.
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.
NLO QCD corrections in Herwig++ with MC@NLO
Stefano Frixione; Fabian Stoeckli; Paolo Torrielli; Bryan R. Webber
2010-10-04T23:59:59.000Z
We present the calculations necessary to obtain next-to-leading order QCD precision with the Herwig++ event generator using the MC@NLO approach, and implement them for all the processes that were previously available from Fortran HERWIG with MC@NLO. We show a range of results comparing the two implementations. With these calculations and recent developments in the automatic generation of NLO matrix elements, it will be possible to obtain NLO precision with Herwig++ for a much wider range of processes
Observable dark radiation from cosmologically safe QCD axion
Kawasaki, Masahiro; Yanagida, Tsutomu T
2015-01-01T23:59:59.000Z
We propose a QCD axion model that avoids the cosmological domain wall problem, introducing a global SU(3)_f family symmetry to which we embed the unwanted PQ discrete symmetry. The spontaneous breaking of SU(3)_f and PQ symmetry predicts eight NG bosons as well as axion, all of which contribute to dark radiation in the Universe. The derivation from the standard model prediction of dark radiation can be observed by future observations of CMB fluctuations. Our model also predicts a sizable exotic kaon decay rate, which is marginally consistent with the present collider data and would be tested by future collider experiments.
Volume dependence of light hadron masses in full lattice QCD
B. Orth; T. Lippert; K. Schilling
2003-09-15T23:59:59.000Z
The aim of the GRAL project is to simulate full QCD with standard Wilson fermions at light quark masses on small to medium-sized lattices and to obtain infinite-volume results by extrapolation. In order to establish the functional form of the volume dependence we study systematically the finite-size effects in the light hadron spectrum. We give an update on the status of the GRAL project and show that our simulation data for the light hadron masses depend exponentially on the lattice size.
Yang Ma; Xing-Gang Wu; Hong-Hao Ma; Hua-Yong Han
2015-03-17T23:59:59.000Z
As one of the key components of perturbative QCD theory, it is helpful to find a systematic and reliable way to set the renormalization scale for a high-energy process. The conventional treatment is to take a typical momentum as the renormalization scale, which assigns an arbitrary range and an arbitrary systematic error to pQCD predictions, leading to the well-known renormalization scheme and scale ambiguities. As a practical solution for such scale setting problem, the "Principle of Minimum Sensitivity" (PMS), has been proposed in the literature. The PMS suggests to determine an optimal scale for the pQCD approximant of an observable by requiring its slope over the scheme and scale changes to vanish. In the paper, we present a detailed discussion on general properties of PMS by utilizing three quantities $R_{e^+e^-}$, $R_\\tau$ and $\\Gamma(H\\rightarrow b\\bar{b})$ up to four-loop QCD corrections. After applying the PMS, the accuracy of pQCD prediction, the pQCD convergence, the pQCD predictive power and etc., have been discussed. Furthermore, we compare PMS with another fundamental scale setting approach, i.e. the Principle of Maximum Conformality (PMC)... Our results show that PMS does provide a practical way to set the effective scale for high-energy process, and the PMS prediction agrees with the PMC one by including enough high-order QCD corrections, both of which shall be more accurate than the prediction under the conventional scale setting. However, the PMS pQCD convergence is an accidental, which usually fails to achieve a correct prediction of unknown high-order contributions with next-to-leading order QCD correction only, i.e. it is always far from the "true" values predicted by including more high-order contributions.
Quantum realism and quantum surrealism
Mateus Araújo
2014-08-29T23:59:59.000Z
In this thesis we explore the questions of what should be considered a "classical" theory, and which aspects of quantum theory cannot be captured by any theory that respects our intuition of classicality. This exploration is divided in two parts: in the first we review classical results of the literature, such as the Kochen-Specker theorem, von Neumann's theorem, Gleason's theorem, as well as more recent ideas, such as the distinction between $\\psi$-ontic and $\\psi$-epistemic ontological models, Spekkens' definition of contextuality, Hardy's ontological excess baggage theorem and the PBR theorem. The second part is concerned with pinning down what should be the "correct" definition of contextuality. We settle down on the definition advocated by Abramsky and Branderburger, motivated by the Fine theorem, and show the connection of this definition with the work of George Boole. This definition allows us to unify the notions of locality and noncontextuality, and use largely the same tools to characterize how quantum mechanics violates these notions of classicality. Exploring this formalism, we find a new family of noncontextuality inequalities. We conclude by reviewing the notion of state-independent contextuality.
Stochastic propagators for multi-pion correlation functions in lattice QCD with GPUs
Joel Giedt; Dean Howarth
2014-08-11T23:59:59.000Z
Motivated by the application of L\\"uscher's finite volume method to the study of the lightest scalar resonance in the $\\pi\\pi \\to \\pi\\pi$ isoscalar channel, in this article we describe our studies of multi-pion correlation functions computed using stochastic propagators in quenched lattice QCD, harnessing GPUs for acceleration. We consider two methods for constructing the correlation functions. One "outer product" approach becomes quite expensive at large lattice extent $L$, having an ${\\cal O}(L^7)$ scaling. The other "stochastic operator" approach scales as ${\\cal O}(N_r^2 L^4)$, where $N_r$ is the number of random sources. It would become more efficient if variance reduction techniques are used and the volume is fairly large. It is also found that correlations between stochastic propagators appearing in the same diagram, when a single set of random source vectors is used, lead to much larger errors than if separate random sources are used for each propagator. The calculations involve states with quantum numbers of the vacuum, so all-to-all propagators must be computed. For this reason, GPUs are ideally suited to accelerating the calculation. For this work we have integrated the Columbia Physics System (CPS) and QUDA GPU inversion library, in the case of clover fermions. Finally, we show that the completely quark disconnected diagram is crucial to the results, and that neglecting it would lead to answers which are far from the true value for the effective mass in this channel. This is unfortunate, because as we also show, this diagram has very large errors, and in fact dominates the error budget.
Proposal for feasible experiments of cold-atom quantum simulator of U(1) lattice gauge-Higgs model
Yoshihito Kuno; Kenichi Kasamatsu; Yoshiro Takahashi; Ikuo Ichinose; Tetsuo Matsui
2014-12-24T23:59:59.000Z
Lattice gauge theory has provided us with a crucial non-perturbative method in studying canonical models in high-energy physics such as quantum chromodynamics. Among other models of lattice gauge theory, the lattice gauge-Higgs model is a quite important one because it describes wide variety of phenomena/models related to the Anderson-Higgs mechanism such as superconductivity, the standard model of particle physics, and inflation process of the early universe. In this paper, to realize a quantum simulator of the U(1) lattice gauge-Higgs model on an optical lattice filled by cold atoms, we propose two feasible methods: (i) Wannier states in the excited bands and (ii) dipolar atoms in a multilayer optical lattice. We pay attentions to respect the constraint of Gauss's law and avoid nonlocal gauge interactions. Numerical simulations of the time development of an electric flux by using the Gross-Pitaevskii equations reveal some interesting characteristics of dynamical aspect of the model.
Bootstrapping Multi-Parton Loop Amplitudes in QCD
Bern, Zvi; /UCLA; Dixon, Lance J.; /SLAC; Kosower, David A.; /Saclay, SPhT
2005-07-06T23:59:59.000Z
The authors present a new method for computing complete one-loop amplitudes, including their rational parts, in non-supersymmetric gauge theory. This method merges the unitarity method with on-shell recursion relations. It systematizes a unitarity-factorization bootstrap approach previously applied by the authors to the one-loop amplitudes required for next-to-leading order QCD corrections to the processes e{sup +}e{sup -} {yields} Z, {gamma}* {yields} 4 jets and pp {yields} W + 2 jets. We illustrate the method by reproducing the one-loop color-ordered five-gluon helicity amplitudes in QCD that interfere with the tree amplitude, namely A{sub 5;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}) and A{sub 5;1}(1{sup -}, 2{sup +}, 3{sup -}, 4{sup +}, 5{sup +}). Then we describe the construction of the six- and seven-gluon amplitudes with two adjacent negative-helicity gluons, A{sub 6;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}) and A{sub 7;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}, 7{sup +}), which uses the previously-computed logarithmic parts of the amplitudes as input. They present a compact expression for the six-gluon amplitude. No loop integrals are required to obtain the rational parts.
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.
High temperature QCD with three flavors of improved staggered quarks
The MILC Collaboration; C. Bernard; T. Burch; C. E. DeTar; Steven Gottlieb; Eric Gregory; U. M. Heller; J. Osborn; R. L. Sugar; D. Toussaint
2002-09-05T23:59:59.000Z
We present an update of our study of high temperature QCD with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad staggered quark action. Simulations are being carried out on lattices with Nt=4, 6 and 8 for the case of three degenerate quarks with masses less than or equal to the strange quark mass, $m_s$, and on lattices with Nt=6 and 8 for degenerate up and down quarks with masses in the range 0.2 m_s \\leq m_{u,d} \\leq 0.6 m_s, and the strange quark fixed near its physical value. We also report on first computations of quark number susceptibilities with the Asqtad action. These susceptibilities are of interest because they can be related to event-by-event fluctuations in heavy ion collision experiments. Use of the improved quark action leads to a substantial reduction in lattice artifacts. This can be seen already for free fermions and carries over into our results for QCD.
High temperature QCD with three flavors of improved staggered quarks
Bernard, C; DeTar, C E; Gottlieb, S; Gregory, E; Heller, U M; Osborn, J; Sugar, R L; Toussaint, D; Gottlieb, Steven; Gregory, Eric
2002-01-01T23:59:59.000Z
We present an update of our study of high temperature QCD with three flavors of quarks, using a Symanzik improved gauge action and the Asqtad staggered quark action. Simulations are being carried out on lattices with Nt=4, 6 and 8 for the case of three degenerate quarks with masses less than or equal to the strange quark mass, $m_s$, and on lattices with Nt=6 and 8 for degenerate up and down quarks with masses in the range 0.2 m_s \\leq m_{u,d} \\leq 0.6 m_s, and the strange quark fixed near its physical value. We also report on first computations of quark number susceptibilities with the Asqtad action. These susceptibilities are of interest because they can be related to event-by-event fluctuations in heavy ion collision experiments. Use of the improved quark action leads to a substantial reduction in lattice artifacts. This can be seen already for free fermions and carries over into our results for QCD.
QCD sum rule determination of the charm-quark mass
Bodenstein, S. [Centre for Theoretical and Mathematical Physics, University of Cape Town, Rondebosch 7700 (South Africa); Bordes, J.; Penarrocha, J. [Departamento de Fisica Teorica, Universitat de Valencia, and Instituto de Fisica Corpuscular, Centro Mixto Universitat de Valencia-CSIC (Spain); Dominguez, C. A. [Centre for Theoretical and Mathematical Physics, University of Cape Town, Rondebosch 7700 (South Africa); Department of Physics, Stellenbosch University, Stellenbosch 7600 (South Africa); Schilcher, K. [Institut fuer Physik, Johannes Gutenberg-Universitaet Staudingerweg 7, D-55099 Mainz (Germany)
2011-04-01T23:59:59.000Z
QCD sum rules involving mixed inverse moment integration kernels are used in order to determine the running charm-quark mass in the MS scheme. Both the high and the low energy expansion of the vector current correlator are involved in this determination. The optimal integration kernel turns out to be of the form p(s)=1-(s{sub 0}/s){sup 2}, where s{sub 0} is the onset of perturbative QCD. This kernel enhances the contribution of the well known narrow resonances, and reduces the impact of the data in the range s{approx_equal}20-25 GeV{sup 2}. This feature leads to a substantial reduction in the sensitivity of the results to changes in s{sub 0}, as well as to a much reduced impact of the experimental uncertainties in the higher resonance region. The value obtained for the charm-quark mass in the MS scheme at a scale of 3 GeV is m{sub c}(3 GeV)=987{+-}9 MeV, where the error includes all sources of uncertainties added in quadrature.
WIMP Dark Matter and the QCD Equation of State
Mark Hindmarsh; Owe Philipsen
2005-01-25T23:59:59.000Z
Weakly Interacting Massive Particles (WIMPs) of mass m freeze out at a temperature T_f ~ m/25, i.e. in the range 400 MeV -- 40 GeV for a particle in the typical mass range 10 -- 1000 GeV. The WIMP relic density, which depends on the effective number of relativistic degrees of freedom at T_f, may be measured to better than 1% by Planck, warranting comparable theoretical precision. Recent theoretical and experimental advances in the understanding of high temperature QCD show that the quark gluon plasma departs significantly from ideal behaviour up to temperatures of several GeV, necessitating an improvement of the cosmological equation of state over those currently used. We discuss how this increases the relic density by approximately 1.5 -- 3.5% in benchmark mSUGRA models, with an uncertainly in the QCD corrections of 0.5 -- 1 %. We point out what further work is required to achieve a theoretical accuracy comparable with the expected observational precision, and speculate that the effective number of degrees of freedom at T_f may become measurable in the foreseeable future.
Wave Function of the Roper from Lattice QCD
Dale S. Roberts; Waseem Kamleh; Derek B. Leinweber
2013-07-26T23:59:59.000Z
We apply the eigenvectors from a variational analysis in lattice QCD to successfully extract the wave function of the Roper state, and a higher mass P_11 state of the nucleon. We use the 2+1 flavour 32^3x64 PACS-CS configurations at a near physical pion mass of 156 MeV. We find that both states exhibit a structure consistent with a constituent quark model. The Roper d-quark wave function contains a single node consistent with a 2S state, and the third state wave function contains two, consistent with a 3S state. A detailed comparison with constituent quark model wave functions is carried out, obtained from a Coulomb plus ramp potential. These results validate the approach of accessing these states by constructing a variational basis composed of different levels of fermion source and sink smearing. Furthermore, significant finite volume effects are apparent for these excited states which mix with multi-particle states, driving their masses away from physical values and enabling the extraction of resonance parameters from lattice QCD simulations.
The pion transition form factor and the pion distribution amplitude
S. Noguera; V. Vento
2010-01-18T23:59:59.000Z
Recent BaBaR data on the pion transition form factor, whose Q^2 dependence is much steeper then predicted by asymptotic Quantum Chromodynamics (QCD), have caused a renewed interest in its theoretical description. We present here a formalism based on a model independent low energy description and a high energy description based on QCD, which match at a scale Q_0. The high energy description incorporates a flat pion distribution amplitude, phi(x)=1, at the matching scale Q_0 and QCD evolution from Q_0 to Q>Q_0. The flat pion distribution is connected, through soft pion theorems and chiral symmetry, to the pion valance parton distribution at the same low scale Q_0. The procedure leads to a good description of the data, and incorporating additional twist three effects, to an excellent description of the data.
Dmitri E. Kharzeev; Larry D. McLerran; Harmen J. Warringa
2007-11-06T23:59:59.000Z
Quantum chromodynamics (QCD) contains field configurations which can be characterized by a topological invariant, the winding number Q_w. Configurations with nonzero Q_w break the charge-parity CP symmetry of QCD. We consider a novel mechanism by which these configurations can separate charge in the presence of a background magnetic field - the "Chiral Magnetic Effect". We argue that sufficiently large magnetic fields are created in heavy ion collisions so that the Chiral Magnetic Effect causes preferential emission of charged particles along the direction of angular momentum. Since separation of charge is CP-odd, any observation of the Chiral Magnetic Effect could provide a clear demonstration of the topological nature of the QCD vacuum. We give an estimate of the effect and conclude that it might be observed experimentally.
U. Alvarez-Rodriguez; M. Sanz; L. Lamata; E. Solano
2015-05-29T23:59:59.000Z
Quantum information provides fundamentally different computational resources than classical information. We prove that there is no unitary protocol able to add unknown quantum states belonging to different Hilbert spaces. This is an inherent restriction of quantum physics that is related to the impossibility of copying an arbitrary quantum state, i.e., the no-cloning theorem. Moreover, we demonstrate that a quantum adder, in absence of an ancillary system, is also forbidden for a known orthonormal basis. This allows us to propose an approximate quantum adder that could be implemented in the lab. Finally, we discuss the distinct character of the forbidden quantum adder for quantum states and the allowed quantum adder for density matrices.
Advances in Quantum Teleportation
Pirandola, Stefano; Weedbrook, Christian; Furusawa, Akira; Braunstein, Samuel L
2015-01-01T23:59:59.000Z
Quantum teleportation is one of the most important protocols in quantum information. By exploiting the physical resource of entanglement, quantum teleportation serves as a key primitive in a variety of quantum information tasks and represents an important building block for quantum technologies, with a pivotal role in the continuing progress of quantum communication, quantum computing and quantum networks. Here we review the basic theoretical ideas behind quantum teleportation and its variant protocols. We focus on the main experiments, together with the technical advantages and disadvantages associated with the use of the various technologies, from photonic qubits and optical modes to atomic ensembles, trapped atoms, and solid-state systems. Analysing the current state-of-the-art, we finish by discussing open issues, challenges and potential future implementations.
C. B. Compean; M. Kirchbach
2006-03-26T23:59:59.000Z
We present the quantum mechanics problem of the one-dimensional Schroedinger equation with the trigonometric Rosen-Morse potential. This potential is of possible interest to quark physics in so far as it captures the essentials of the QCD quark-gluon dynamics and (i) interpolates between a Coulomb-like potential (associated with one-gluon exchange) and the infinite wall potential (associated with asymptotic freedom), (ii) reproduces in the intermediary region the linear confinement potential (associated with multi-gluon self-interactions) as established by lattice QCD calculations of hadron properties. Moreover, its exact real solutions given here display a new class of real orthogonal polynomials and thereby interesting mathematical entities in their own.
High detectivity short-wavelength II-VI quantum cascade detector
Ravikumar, Arvind P., E-mail: aravikum@princeton.edu; Gmachl, Claire F. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Garcia, Thor A.; Tamargo, Maria C. [Department of Chemistry, The Graduate Center and The City College of New York, CUNY, New York, New York 10031 (United States); Jesus, Joel De [Department of Physics, The Graduate Center and The City College of New York, CUNY, New York, New York 10031 (United States)
2014-08-11T23:59:59.000Z
We report on the experimental demonstration of a ZnCdSe/ZnCdMgSe-based short-wavelength photovoltaic Quantum Cascade Detector (QCD). The QCD operates in two spectral bands centered around 2.6??m and 3.6??m. Calibrated blackbody measurements yield a peak responsivity of 0.1?mA/W or 2400?V/W at 80?K, and a corresponding 300?K background radiation limited infrared performance detectivity (BLIP) of ?2.5?×?10{sup 10?}cm ?Hz/W. Comparison of background illuminated and dark current-voltage measurements demonstrates a BLIP temperature of 200?K. The device differential resistance-area product, decreases from about 10{sup 6} ? cm{sup 2} at 80?K to about 8000 ? cm{sup 2} at 300?K, indicative of the ultra-low Johnson noise in the detectors.
One-loop calculations in quantum field theory: from Feynman diagrams to unitarity cuts
Ellis, R. Keith [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Kunszt, Zoltan [Institute for Theoretical Physics (Switzerland); Melnikov, Kirill [Johns Hopkins Univ., Baltimore, MD (United States); Zanderighi, Giulia [Rudolf Peierls Centre for Theoretical Physics (United Kingdom)
2012-09-01T23:59:59.000Z
The success of the experimental program at the Tevatron re-inforced the idea that precision physics at hadron colliders is desirable and, indeed, possible. The Tevatron data strongly suggests that one-loop computations in QCD describe hard scattering well. Extrapolating this observation to the LHC, we conclude that knowledge of many short-distance processes at next-to-leading order may be required to describe the physics of hard scattering. While the field of one-loop computations is quite mature, parton multiplicities in hard LHC events are so high that traditional computational techniques become inefficient. Recently new approaches based on unitarity have been developed for calculating one-loop scattering amplitudes in quantum field theory. These methods are especially suitable for the description of multi-particle processes in QCD and are amenable to numerical implementations. We present a systematic pedagogical description of both conceptual and technical aspects of the new methods.
Quantum thermodynamics of general quantum processes
Felix C. Binder; Sai Vinjanampathy; Kavan Modi; John Goold
2015-03-27T23:59:59.000Z
Accurately describing work extraction from a quantum system is a central objective for the extension of thermodynamics to individual quantum systems. The concepts of work and heat are surprisingly subtle when generalizations are made to arbitrary quantum states. We formulate an operational thermodynamics suitable for application to an open quantum system undergoing quantum evolution under a general quantum process by which we mean a completely-positive and trace-preserving map. We derive an operational first law of thermodynamics for such processes and show consistency with the second law. We show that heat, from the first law, is positive when the input state of the map majorises the output state. Moreover, the change in entropy is also positive for the same majorisation condition. This makes a strong connection between the two operational laws of thermodynamics.
Quantum Evolution and Anticipation
Hans-Rudolf Thomann
2010-03-04T23:59:59.000Z
In a previous paper we have investigated quantum states evolving into mutually orthogonal states at equidistant times, and the quantum anticipation effect exhibited by measurements at one half step. Here we extend our analyzes of quantum anticipation to general type quantum evolutions and spectral measures and prove that quantum evolutions possessing an embedded orthogonal evolution are characterized by positive joint spectral measure. Furthermore, we categorize quantum evolution, assess anticipation strength and provide a framework of analytic tools and results, thus preparing for further investigation and experimental verification of anticipation in concrete physical situations such as the H-atom, which we have found to exhibit anticipation.
Robert Carroll
2007-11-05T23:59:59.000Z
We show some relations between Ricci flow and quantum theory via Fisher information and the quantum potential.
QCD uncertainties in the prediction of B --> K^* mu^+ mu^- observables
Sébastien Descotes-Genon; Lars Hofer; Joaquim Matias; Javier Virto
2014-11-04T23:59:59.000Z
The recent LHCb angular analysis of the exclusive decay B --> K^* mu^+ mu^- has indicated significant deviations from the Standard Model expectations. In order to give precise theory predictions, it is crucial that uncertainties from non-perturbative QCD are under control and properly included. The dominant QCD uncertainties originate from the hadronic B --> K^* form factors and from charm loops. We present a systematic method to include factorisable power corrections to the form factors in the framework of QCD factorisation and study the impact of the scheme chosen to define the soft form factors. We also discuss charm-loop effects.
Jet Substructure Templates: Data-driven QCD Backgrounds for Fat Jet Searches
Timothy Cohen; Martin Jankowiak; Mariangela Lisanti; Hou Keong Lou; Jay G. Wacker
2014-10-20T23:59:59.000Z
QCD is often the dominant background to new physics searches for which jet substructure provides a useful handle. Due to the challenges associated with modeling this background, data-driven approaches are necessary. This paper presents a novel method for determining QCD predictions using templates -- probability distribution functions for jet substructure properties as a function of kinematic inputs. Templates can be extracted from a control region and then used to compute background distributions in the signal region. Using Monte Carlo, we illustrate the procedure with two case studies and show that the template approach effectively models the relevant QCD background. This work strongly motivates the application of these techniques to LHC data.
Lattice QCD and Hydro/Cascade Model of Heavy Ion Collisions
Michael Cheng
2010-05-11T23:59:59.000Z
We report here on a recent lattice study of the QCD transition region at finite temperature and zero chemical potential using domain wall fermions (DWF). We also present a parameterization of the QCD equation of state obtained from lattice QCD that is suitable for use in hydrodynamics studies of heavy ion collisions. Finally, we show preliminary results from a multi-stage hydrodynamics/hadron cascade model of a heavy ion collision, in an attempt to understand how well the experimental data (e.g. particle spectra, elliptic flow, and HBT radii) can constrain the inputs (e.g. initial temperature, freezeout temperature, shear viscosity, equation of state) of the theoretical model.
Free energy of static quarks and the renormalized Polyakov loop in full QCD
K. Petrov; for the RBC-Bielefeld Collaboration
2007-10-23T23:59:59.000Z
We present results from a detailed study of singlet free energies in full QCD with realistic quark masses. An improved scheme for the non-perturbative renormalization of the Polyakov loop is used and we compare its temperature dependence for QCD with different flavor content. We also analyze screening masses extracted from singlet free energies at various temperatures close to and above the QCD transition temperature. We conclude that the temperature dependence of screening masses is well described by perturbation theory up to a non-perturbative pre-factor. An effective running coupling has been determined for all temperature values giving additional insight into screening phenomena at high temperature.
Lambda Phenomena: the Lambda points of liquid Helium and chiral QCD
Sourendu Gupta; Rishi Sharma
2015-03-11T23:59:59.000Z
The superfluid transition of liquid Helium shares an interesting phenomenon with the chiral limit of QCD: the specific heat is finite at the critical point, but has a cusp. From this follows an interesting mixture of universal and non-universal features at the critical point. Through the CP symmetry of chiral QCD, this has implications for the fourth order baryon number susceptibility and susceptibilities of higher orders. Investigations of such a scaling will show us whether O(4) scaling is an accurate description of baryon-free QCD when the pion mass is realistic.
Lambda Phenomena: the Lambda points of liquid Helium and chiral QCD
Gupta, Sourendu
2015-01-01T23:59:59.000Z
The superfluid transition of liquid Helium shares an interesting phenomenon with the chiral limit of QCD: the specific heat is finite at the critical point, but has a cusp. From this follows an interesting mixture of universal and non-universal features at the critical point. Through the CP symmetry of chiral QCD, this has implications for the fourth order baryon number susceptibility and susceptibilities of higher orders. Investigations of such a scaling will show us whether O(4) scaling is an accurate description of baryon-free QCD when the pion mass is realistic.
Anwar Bhatti; Don Lincoln
2010-02-23T23:59:59.000Z
Jets have been used to verify the theory of quantum chromodynamics (QCD), measure the structure of the proton and to search for the physics beyond the Standard Model. In this article, we review the current status of jet physics at the Tevatron, a sqrt(s) = 1.96 TeV p-pbar collider at the Fermi National Accelerator Laboratory. We report on recent measurements of the inclusive jet production cross section and the results of searches for physics beyond the Standard Model using jets. Dijet production measurements are also reported.
The beam energy dependence of collective flow in heavy ion collisions
Petersen, Hannah; Auvinen, Jussi; Bleicher, Marcus
2015-01-01T23:59:59.000Z
The major goals of heavy ion research are to explore the phase diagram of quantum chromodynamics (QCD) and to investigate the properties of the quark gluon plasma (QGP), a new state of matter created at high temperatures and/or densities. Collective anisotropic flow is one of the most promising observables to gain insights about the properties of the system created in relativistic heavy ion reactions. The current status of the beam energy dependence of the first three Fourier coefficients of the azimuthal distribution of the produced particles $v_1$ to $v_3$ within hybrid transport plus hydrodynamics approaches are summarized.
The beam energy dependence of collective flow in heavy ion collisions
Hannah Petersen; Jan Steinheimer; Jussi Auvinen; Marcus Bleicher
2015-03-11T23:59:59.000Z
The major goals of heavy ion research are to explore the phase diagram of quantum chromodynamics (QCD) and to investigate the properties of the quark gluon plasma (QGP), a new state of matter created at high temperatures and/or densities. Collective anisotropic flow is one of the most promising observables to gain insights about the properties of the system created in relativistic heavy ion reactions. The current status of the beam energy dependence of the first three Fourier coefficients of the azimuthal distribution of the produced particles $v_1$ to $v_3$ within hybrid transport plus hydrodynamics approaches are summarized.
POLYSHIFT Communications Software for the Connection Machine System CM-200
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
George, William; Brickner, Ralph G.; Johnsson, S. Lennart
1994-01-01T23:59:59.000Z
We describe the use and implementation of a polyshift function PSHIFT for circular shifts and end-offs shifts. Polyshift is useful in many scientific codes using regular grids, such as finite difference codes in several dimensions, and multigrid codes, molecular dynamics computations, and in lattice gauge physics computations, such as quantum chromodynamics (QCD) calculations. Our implementation of the PSHIFT function on the Connection Machine systems CM-2 and CM-200 offers a speedup of up to a factor of 3–4 compared with CSHIFT when the local data motion within a node is small. The PSHIFT routine is included in the Connection Machine Scientificmore »Software Library (CMSSL).« less
Nuclear enhanced power corrections to DIS structure functions
Xiaofeng Guo; Jianwei Qiu; Wei Zhu
2001-10-03T23:59:59.000Z
We calculate nuclear enhanced power corrections to structure functions measured in deeply inelastic lepton-nucleus scattering in Quantum Chromodynamics (QCD). We find that the nuclear medium enhanced power corrections at order of $O(\\alpha_s/Q^2)$ enhance the longitudinal structure function $F_L$, and suppress the transverse structure function $F_1$. We demonstrate that strong nuclear effects in $\\sigma_A/\\sigma_D$ and $R_A/R_D$, recently observed by HERMES Collaboration, can be explained in terms of the nuclear enhanced power corrections.
Chemical freeze-out parameters in Beam Energy Scan Program of STAR at RHIC
Sabita Das
2014-12-01T23:59:59.000Z
The STAR experiment at RHIC has completed its first phase of the Beam Energy Scan (BES-I) program to understand the phase structure of the quantum chromodynamics (QCD). The bulk properties of the system formed in Au+Au collisions at different center of mass energy $\\sqrt{s_{NN}} = $ 7.7, 11.5, 19.6, 27, and 39 GeV have been studied from the data collected in the year 2010 and 2011. The centrality and energy dependence of mid-rapidity ($|y|$ chemical freeze-out parameters are extracted using measured particle ratios within the framework of a statistical model.
Keller, Dustin M. [University of Virginia; Hicks, Kenneth H. [OHIO
2013-05-01T23:59:59.000Z
The transition magnetic moments for decuplet-to-octet baryon electromagnetic decays are calculated from the CLAS experimental results and are compared with calculations to first order in the 1/N{sub c} expansion of quantum chromodynamics (QCD) and new U-spin predictions. Using the U-spin predictions for the {Sigma} *{sup 0} --> {Sigma}{sup 0} {gamma} and {Sigma} *{sup +} ? {Sigma}{sup +} {gamma} decays, the SU(3)-forbidden transition {Sigma} *{sup -} ? {Sigma}{sup -} {gamma} is obtained. In addition, the doubly strange baryon radiative decay {Xi} *{sup 0} ? {Xi} {gamma} is predicted using U-spin.
Charmonium properties in deconfinement phase in anisotropic lattice QCD
H. Iida; T. Doi; N. Ishii; H. Suganuma; K. Tsumura
2006-06-14T23:59:59.000Z
J/Psi and eta_c above the QCD critical temperature T_c are studied in anisotropic quenched lattice QCD, considering whether the c\\bar c systems above T_c are spatially compact (quasi-)bound states or scattering states. We adopt the standard Wilson gauge action and O(a)-improved Wilson quark action with renormalized anisotropy a_s/a_t =4.0 at \\beta=6.10 on 16^3\\times (14-26) lattices, which correspond to the spatial lattice volume V\\equiv L^3\\simeq(1.55{\\rm fm})^3 and temperatures T\\simeq(1.11-2.07)T_c. We investigate the c\\bar c system above T_c from the temporal correlators with spatially-extended operators, where the overlap with the ground state is enhanced. To clarify whether compact charmonia survive in the deconfinement phase, we investigate spatial boundary-condition dependence of the energy of c\\bar c systems above T_c. In fact, for low-lying S-wave c \\bar c scattering states, it is expected that there appears a significant energy difference \\Delta E \\equiv E{\\rm (APBC)}-E{\\rm (PBC)}\\simeq2\\sqrt{m_c^2+3\\pi^2/L^2}-2m_c (m_c: charm quark mass) between periodic and anti-periodic boundary conditions on the finite-volume lattice. In contrast, for compact charmonia, there is no significant energy difference between periodic and anti-periodic boundary conditions. As a lattice QCD result, almost no spatial boundary-condition dependence is observed for the energy of the c\\bar c system in J/\\Psi and \\eta_c channels for T\\simeq(1.11-2.07)T_c. This fact indicates that J/\\Psi and \\eta_c would survive as spatially compact c\\bar c (quasi-)bound states below 2T_c. We also investigate a $P$-wave channel at high temperature with maximally entropy method (MEM) and find no low-lying peak structure corresponding to \\chi_{c1} at 1.62T_c.
(Pseudo)scalar charmonium in finite temperature QCD
Dominguez, C. A. [Centre for Theoretical and Mathematical Physics, University of Cape Town, Rondebosch 7700 (South Africa); Department of Physics, Stellenbosch University, Stellenbosch 7600 (South Africa); Loewe, M. [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Rojas, J. C. [Departamento de Fisica, Universidad Catolica del Norte, Casilla 1280, Antofagasta (Chile); Zhang, Y. [Centre for Theoretical and Mathematical Physics, University of Cape Town, Rondebosch 7700 (South Africa)
2011-02-01T23:59:59.000Z
The hadronic parameters of pseudoscalar ({eta}{sub c}) and scalar ({chi}{sub c}) charmonium are determined at finite temperature from Hilbert moment QCD sum rules. These parameters are the hadron mass, leptonic decay constant, total width, and continuum threshold (s{sub 0}). Results for s{sub 0}(T) in both channels indicate that s{sub 0}(T) starts approximately constant, and then it decreases monotonically with increasing T until it reaches the QCD threshold, s{sub th}=4m{sub Q}{sup 2}, at a critical temperature T=T{sub c{approx_equal}}180 MeV interpreted as the deconfinement temperature. The other hadronic parameters behave qualitatively similarly to those of the J/{psi}, as determined in this same framework. The hadron mass is essentially constant, the total width is initially independent of T, and after T/T{sub c{approx_equal}}0.80 it begins to increase with increasing T up to T/T{sub c{approx_equal}}0.90(0.95) for {chi}{sub c} ({eta}{sub c}), and subsequently it decreases sharply up to T{approx_equal}0.94(0.99)T{sub c}, for {chi}{sub c} ({eta}{sub c}), beyond which the sum rules are no longer valid. The decay constant of {chi}{sub c} at first remains basically flat up to T{approx_equal}0.80T{sub c}, then it starts to decrease up to T{approx_equal}0.90T{sub c}, and finally it increases sharply with increasing T. In the case of {eta}{sub c} the decay constant does not change up to T{approx_equal}0.80T{sub c} where it begins a gentle increase up to T{approx_equal}0.95T{sub c} beyond which it increases dramatically with increasing T. This behavior contrasts with that of light-light and heavy-light quark systems, and it suggests the survival of the {eta}{sub c} and the {chi}{sub c} states beyond the critical temperature, as already found for the J/{psi} from similar QCD sum rules. These conclusions are very stable against changes in the critical temperature in the wide range T{sub c}=180-260 MeV.
Quantum convolutional stabilizer codes
Chinthamani, Neelima
2004-09-30T23:59:59.000Z
Quantum error correction codes were introduced as a means to protect quantum information from decoherance and operational errors. Based on their approach to error control, error correcting codes can be divided into two different classes: block codes...
Friedenauer, Axel; Glückert, Jan Tibor; Porras, Diego; Schätz, Tobias
2008-01-01T23:59:59.000Z
To gain deeper insight into the dynamics of complex quantum systems we need a quantum leap in computer simulations. We can not translate quantum behaviour arising with superposition states or entanglement efficiently into the classical language of conventional computers. The final solution to this problem is a universal quantum computer [1], suggested in 1982 and envisioned to become functional within the next decade(s); a shortcut was proposed via simulating the quantum behaviour of interest in a different quantum system, where all parameters and interactions can be controlled and the outcome detected sufficiently well. Here we study the feasibility of a quantum simulator based on trapped ions [2]. We experimentally simulate the adiabatic evolution of the smallest non-trivial spin system from the paramagnetic into the (anti-)ferromagnetic order with a quantum magnetisation for two spins of 98%, controlling and manipulating all relevant parameters of the Hamiltonian independently via electromagnetic fields. W...
Svetlichny, George
2011-01-01T23:59:59.000Z
I contemplate the idea that the subjective world and quantum state reductions are one and the same. If true, this resolves with one stroke both the quantum mechanical measurement problem and the hard problem of consciousness.
George Svetlichny
2011-04-13T23:59:59.000Z
I contemplate the idea that the subjective world and quantum state reductions are one and the same. If true, this resolves with one stroke both the quantum mechanical measurement problem and the hard problem of consciousness.
H. Niemi; K. J. Eskola; R. Paatelainen
2015-05-11T23:59:59.000Z
We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order perturbative QCD using a saturation conjecture to control soft particle production, and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries, against the LHC and RHIC measurements. We compare also the computed event-by-event probability distributions of relative fluctuations of elliptic flow, and event-plane angle correlations, with the experimental data from Pb+Pb collisions at the LHC. We show how such a systematic multi-energy and multi-observable analysis tests the initial state calculation and the applicability region of hydrodynamics, and in particular how it constrains the temperature dependence of the shear viscosity-to-entropy ratio of QCD matter in its different phases in a remarkably consistent manner.
Jae-Suk Park; John Terilla; Thomas Tradler
2009-09-21T23:59:59.000Z
We introduce the concept of a quantum background and a functor QFT. In the case that the QFT moduli space is smooth formal, we construct a flat quantum superconnection on a bundle over QFT which defines algebraic structures relevant to correlation functions in quantum field theory. We go further and identify chain level generalizations of correlation functions which should be present in all quantum field theories.
A Bayesian analysis of the nucleon QCD sum rules
Keisuke Ohtani; Philipp Gubler; Makoto Oka
2011-10-03T23:59:59.000Z
QCD sum rules of the nucleon channel are reanalyzed, using the maximum entropy method (MEM). This new approach, based on the Bayesian probability theory, does not restrict the spectral function to the usual "pole + continuum"-form, allowing a more flexible investigation of the nucleon spectral function. Making use of this flexibility, we are able to investigate the spectral functions of various interpolating fields, finding that the nucleon ground state mainly couples to an operator containing a scalar diquark. Moreover, we formulate the Gaussian sum rule for the nucleon channel and find that it is more suitable for the MEM analysis to extract the nucleon pole in the region of its experimental value, while the Borel sum rule does not contain enough information to clearly separate the nucleon pole from the continuum.
QCD description of backward vector meson hard electroproduction
B. Pire; K. Semenov-Tian-Shansky; L. Szymanowski
2015-03-10T23:59:59.000Z
We consider backward vector meson exclusive electroproduction off nucleons in the framework of collinear QCD factorization. Nucleon to vector meson transition distribution amplitudes arise as building blocks for the corresponding factorized amplitudes. In the near-backward kinematics, the suggested factorization mechanism results in the dominance of the transverse cross section of vector meson production ($\\sigma_T \\gg \\sigma_L$) and in the characteristic $1/Q^8$-scaling behavior of the cross section. We evaluate nucleon to vector meson TDAs in the cross-channel nucleon exchange model and present estimates of the differential cross section for backward $\\rho^0$, $\\omega$ and $\\phi$ meson production off protons. The resulting cross sections are shown to be measurable in the forthcoming JLab@12 GeV experiments.
Automatic O$(a)$ improvement for twisted-mass QCD
Sinya Aoki; Oliver Bär
2006-10-18T23:59:59.000Z
We present a condition for automatic O$(a)$ improvement in twisted mass lattice QCD, using symmetries of the Symanzik effective theory. If the continuum part of the Symanzik effective theory is invariant under a particular transformation, named $T_1$ in this report, scaling violations of all quantities invariant under $T_1$ transformation are even in the lattice spacing $a$. On the other hand, quantities non-invariant under $T_1$ vanish in the continuum limit with odd powers in $a$. We prove this statement even for the massive case without using the equation of motion. We also consider a few different criteria for the $T_1$ invariant condition in lattice theories and discuss ambiguities of the lattice condition for O$(a)$ improvement.
Physical Point Simulation in 2+1 Flavor Lattice QCD
PACS-CS Collaboration; :; S. Aoki; K. -I. Ishikawa; N. Ishizuka; T. Izubuchi; D. Kadoh; K. Kanaya; Y. Kuramashi; Y. Namekawa; M. Okawa; Y. Taniguchi; A. Ukawa; N. Ukita; T. Yamazaki; T. Yoshie
2010-04-04T23:59:59.000Z
We present the results of the physical point simulation in 2+1 flavor lattice QCD with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action at $\\beta=1.9$ on a $32^3 \\times 64$ lattice. The physical quark masses together with the lattice spacing is determined with $m_\\pi$, $m_K$ and $m_\\Omega$ as physical inputs. There are two key algorithmic ingredients to make possible the direct simulation at the physical point: One is the mass-preconditioned domain-decomposed HMC algorithm to reduce the computational cost. The other is the reweighting technique to adjust the hopping parameters exactly to the physical point. The physics results include the hadron spectrum, the quark masses and the pseudoscalar meson decay constants. The renormalization factors are nonperturbatively evaluated with the Schr{\\"o}dinger functional method. The results are compared with the previous ones obtained by the chiral extrapolation method.
QCD Viscosity to Entropy Density Ratio in the Hadronic Phase
Jiunn-Wei Chen; Yen-Han Li; Yen-Fu Liu; Eiji Nakano
2007-04-20T23:59:59.000Z
Shear viscosity (eta) of QCD in the hadronic phase is computed by the coupled Boltzmann equations of pions and nucleons in low temperatures and low baryon number densities. The eta to entropy density ratio eta/s maps out the nuclear gas-liquid phase transition by forming a valley tracing the phase transition line in the temperature-chemical potential plane. When the phase transition turns into a crossover, the eta/s valley gradually disappears. We suspect the general feature for a first-order phase transition is that eta/s has a discontinuity in the bottom of the eta/s valley. The discontinuity coincides with the phase transition line and ends at the critical point. Beyond the critical point, a smooth eta/s valley is seen. However, the valley could disappear further away from the critical point. The eta/s measurements might provide an alternative to identify the critical points.
Spectral Properties of the Overlap Dirac Operator in QCD
Bietenholz, W; Shcheredin, S
2003-01-01T23:59:59.000Z
We discuss the eigenvalue distribution of the overlap Dirac operator in quenched QCD on lattices of size 8^{4}, 10^{4} and 12^{4} at beta = 5.85 and beta = 6. We distinguish the topological sectors and study the distributions of the leading non-zero eigenvalues, which are stereographically mapped onto the imaginary axis. Thus they can be compared to the predictions of random matrix theory applied to the epsilon-expansion of chiral perturbation theory. We find a satisfactory agreement, if the physical volume exceeds about (1.2 fm)^{4}. For the unfolded level spacing distribution we find an accurate agreement with the random matrix conjecture on all volumes that we considered.
Transverse momentum-dependent parton distribution functions in lattice QCD
Engelhardt, Michael G. [New Mexico State University; Musch, Bernhard U. [Tech. University Munich; Haegler, Philipp G. [Tech. University Munich; Negele, John W. [MIT; Schaefer, Andreas [Regensburg
2013-08-01T23:59:59.000Z
A fundamental structural property of the nucleon is the distribution of quark momenta, both parallel as well as perpendicular to its propagation. Experimentally, this information is accessible via selected processes such as semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process (DY), which can be parametrized in terms of transversemomentum-dependent parton distributions (TMDs). On the other hand, these distribution functions can be extracted from nucleon matrix elements of a certain class of bilocal quark operators in which the quarks are connected by a staple-shaped Wilson line serving to incorporate initial state (DY) or final state (SIDIS) interactions. A scheme for evaluating such matrix elements within lattice QCD is developed. This requires casting the calculation in a particular Lorentz frame, which is facilitated by a parametrization of the matrix elements in terms of invariant amplitudes. Exploratory results are presented for the time-reversal odd Sivers and Boer-Mulders transverse momentum shifts.
Testing Topology Conserving Gauge Actions for Lattice QCD
K. -i. Nagai; K. Jansen; W. Bietenholz; L. Scorzato; S. Necco; S. Shcheredin
2005-09-29T23:59:59.000Z
We explore gauge actions for lattice QCD, which are constructed such that the occurrence of small plaquette values is strongly suppressed. Such actions originate from the admissibility condition in order to conserve the topological charge. The suppression of small plaquette values is expected to be advantageous for numerical studies in the $\\epsilon$-regime and also for simulations with dynamical quarks. Performing simulations at a lattice spacing of about 0.1 fm, we present numerical results for the static potential, the physical scale $r_0$, the stability of the topological charge history, the condition number of the kernel of the overlap operator and the acceptance rate against the step size in the local HMC algorithm.
QPACE -- a QCD parallel computer based on Cell processors
H. Baier; H. Boettiger; M. Drochner; N. Eicker; U. Fischer; Z. Fodor; A. Frommer; C. Gomez; G. Goldrian; S. Heybrock; D. Hierl; M. Hüsken; T. Huth; B. Krill; J. Lauritsen; T. Lippert; T. Maurer; B. Mendl; N. Meyer; A. Nobile; I. Ouda; M. Pivanti; D. Pleiter; M. Ries; A. Schäfer; H. Schick; F. Schifano; H. Simma; S. Solbrig; T. Streuer; K. -H. Sulanke; R. Tripiccione; J. -S. Vogt; T. Wettig; F. Winter
2009-12-24T23:59:59.000Z
QPACE is a novel parallel computer which has been developed to be primarily used for lattice QCD simulations. The compute power is provided by the IBM PowerXCell 8i processor, an enhanced version of the Cell processor that is used in the Playstation 3. The QPACE nodes are interconnected by a custom, application optimized 3-dimensional torus network implemented on an FPGA. To achieve the very high packaging density of 26 TFlops per rack a new water cooling concept has been developed and successfully realized. In this paper we give an overview of the architecture and highlight some important technical details of the system. Furthermore, we provide initial performance results and report on the installation of 8 QPACE racks providing an aggregate peak performance of 200 TFlops.
? b ? ? ? + ? ? form factors and differential branching fraction from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Detmold, William; Lin, C.-J. David; Meinel, Stefan; Wingate, Matthew
2013-04-01T23:59:59.000Z
We present the first lattice QCD determination of the ?b?? transition form factors that govern the rare baryonic decays ?b??l?l? at leading order in heavy-quark effective theory. Our calculations are performed with 2+1 flavors of domain-wall fermions, at two lattice spacings and with pion masses down to 227 MeV. Three-point functions with a wide range of source-sink separations are used to extract the ground-state contributions. The form factors are extrapolated to the physical values of the light-quark masses and to the continuum limit. We use our results to calculate the differential branching fractions for ?b??l?l? with l=e, ?, ? within the standard model. We find agreement with a recent CDF measurement of the ?b?????? differential branching fraction.
QCD thermodynamics with continuum extrapolated Wilson fermions II
Szabolcs Borsanyi; Stephan Durr; Zoltan Fodor; Christian Holbling; Sandor D. Katz; Stefan Krieg; Daniel Nogradi; Kalman K. Szabo; Balint C. Toth; Norbert Trombitas
2015-07-13T23:59:59.000Z
We continue our investigation of 2+1 flavor QCD thermodynamics using dynamical Wilson fermions in the fixed scale approach. Two additional pion masses, approximately 440 MeV and 285 MeV, are added to our previous work at 545 MeV. The simulations were performed at 3 or 4 lattice spacings at each pion mass. The renormalized chiral condensate, strange quark number susceptibility and Polyakov loop is obtained as a function of the temperature and we observe a decrease in the light chiral pseudo-critical temperature as the pion mass is lowered while the pseudo-critical temperature associated with the strange quark number susceptibility or the Polyakov loop is only mildly sensitive to the pion mass. These findings are in agreement with previous continuum results obtained in the staggered formulation.
Toward the excited isoscalar meson spectrum from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Edwards, Robert G. [JLAB; Dudek, Jozef J. [JLAB, Old Dominion U.; Thomas, Christopher Edward [Trinity College, Dublin; Guo, Peng [Indiana U.
2013-11-01T23:59:59.000Z
We report on the extraction of an excited spectrum of isoscalar mesons using lattice QCD. Calculations on several lattice volumes are performed with a range of light quark masses corresponding to pion masses down to about ~400 MeV. The distillation method enables us to evaluate the required disconnected contributions with high statistical precision for a large number of meson interpolating fields. We find relatively little mixing between light and strange in most JPC channels; one notable exception is the pseudoscalar sector where the approximate SU(3)F octet, singlet structure of the ?, ?' is reproduced. We extract exotic JPC states, identified as hybrid mesons in which an excited gluonic field is coupled to a color-octet qqbar pair, along with non-exotic hybrid mesons embedded in a qqbar-like spectrum.
Toward the excited isoscalar meson spectrum from lattice QCD
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Edwards, Robert G.; Dudek, Jozef J.; Thomas, Christopher Edward; Guo, Peng
2013-11-01T23:59:59.000Z
We report on the extraction of an excited spectrum of isoscalar mesons using lattice QCD. Calculations on several lattice volumes are performed with a range of light quark masses corresponding to pion masses down to about ~400 MeV. The distillation method enables us to evaluate the required disconnected contributions with high statistical precision for a large number of meson interpolating fields. We find relatively little mixing between light and strange in most JPC channels; one notable exception is the pseudoscalar sector where the approximate SU(3)F octet, singlet structure of the ?, ?' is reproduced. We extract exotic JPC states, identifiedmore »as hybrid mesons in which an excited gluonic field is coupled to a color-octet qqbar pair, along with non-exotic hybrid mesons embedded in a qqbar-like spectrum.« less
Noncommutative QED+QCD and the {beta} function for QED
Ettefaghi, M. M.; Haghighat, M.; Mohammadi, R. [Department of Physics, Qom University, Qom 371614-6611 (Iran, Islamic Republic of); Department of Physics, Isfahan University of Technology, Isfahan, 84156-83111 (Iran, Islamic Republic of)
2010-11-15T23:59:59.000Z
QED based on {theta}-unexpanded noncomutative space-time in contrast with the noncommutative QED based on {theta}-expanded U(1) gauge theory via the Seiberg-Witten map is one-loop renormalizable. Meanwhile it suffers from asymptotic freedom that is not in agreement with the experiment. We show that the QED part of the U{sub *}(3)xU{sub *}(1) gauge group as an appropriate gauge group for the noncommutative QED+QCD is not only one-loop renormalizable but also has a {beta} function that can be positive, negative and even zero. In fact the {beta} function depends on the mixing parameter {delta}{sub 13} as a free parameter and it will be equal to its counterpart in the ordinary QED for {delta}{sub 13}=0.367{pi}.
Resummation of clustering logarithms for non-global QCD observables
Delenda, Yazid
2013-01-01T23:59:59.000Z
We address the problem of resumming leading clustering logs in QCD jet observables defined using the k_t, CA and SISCone algorithms. We specifically choose the jet mass distribution as an example and calculate up to order(alpha_s^4) clustering-log terms in the series expansion at single-log accuracy. These terms are found to exhibit a pattern of exponentiation and we are thus able to perform an all-orders analytical resummation for the clustering logs. We also numerically calculate the non-global logs at large N_c. We show that our result for the resummation of clustering logs is a very good analytical approximation to the numerical result obtained using a specialised Monte Carlo program.
Toward the excited isoscalar meson spectrum from lattice QCD
Edwards, Robert G. [JLAB; Dudek, Jozef J. [JLAB, Old Dominion U.; Thomas, Christopher Edward [Trinity College, Dublin; Guo, Peng [Indiana U.
2013-11-01T23:59:59.000Z
We report on the extraction of an excited spectrum of isoscalar mesons using lattice QCD. Calculations on several lattice volumes are performed with a range of light quark masses corresponding to pion masses down to about ~400 MeV. The distillation method enables us to evaluate the required disconnected contributions with high statistical precision for a large number of meson interpolating fields. We find relatively little mixing between light and strange in most J^{PC} channels; one notable exception is the pseudoscalar sector where the approximate SU(3)_{F} octet, singlet structure of the ?, ?' is reproduced. We extract exotic J^{PC} states, identified as hybrid mesons in which an excited gluonic field is coupled to a color-octet qqbar pair, along with non-exotic hybrid mesons embedded in a qqbar-like spectrum.
Nuclear matter to strange matter transition in holographic QCD
Youngman Kim; Yunseok Seo; Sang-Jin Sin
2009-11-19T23:59:59.000Z
We construct a simple holographic QCD model to study nuclear matter to strange matter transition. The interaction of dense medium and hadrons is taken care of by imposing the force balancing condition for stable D4/D6/D6 configuration. By considering the intermediate and light flavor branes interacting with baryon vertex homogeneously distributed along R^3 space and requesting the energy minimization, we find that there is a well defined transition density as a function of current quark mass. We also find that as density goes up very high, intermediate (or heavy) and light quarks populate equally as expected from the Pauli principle. In this sense, the effect of the Pauli principle is realized as dynamics of D-branes.
$W^+W^-$ production at hadron colliders in NNLO QCD
T. Gehrmann; M. Grazzini; S. Kallweit; P. Maierhöfer; A. von Manteuffel; S. Pozzorini; D. Rathlev; L. Tancredi
2014-08-22T23:59:59.000Z
Charged gauge boson pair production at the Large Hadron Collider allows detailed probes of the fundamental structure of electroweak interactions. We present precise theoretical predictions for on-shell $W^+W^-$ production that include, for the first time, QCD effects up to next-to-next-to-leading order in perturbation theory. As compared to next-to-leading order, the inclusive $W^+W^-$ cross section is enhanced by 9% at 7 TeV and 12% at 14 TeV. The residual perturbative uncertainty is at the 3% level. The severe contamination of the $W^+W^-$ cross section due to top-quark resonances is discussed in detail. Comparing different definitions of top-free $W^+W^-$ production in the four and five flavour number schemes, we demonstrate that top-quark resonances can be separated from the inclusive $W^+W^-$ cross section without significant loss of theoretical precision.
Phase transition in finite density and temperature lattice QCD
Rui Wang; Ying Chen; Ming Gong; Chuan Liu; Yu-Bin Liu; Zhao-Feng Liu; Jian-Ping Ma; Xiang-Fei Meng; Jian-Bo Zhang
2015-04-09T23:59:59.000Z
We investigate the behavior of the chiral condensate in lattice QCD at finite temperature and finite chemical potential. The study was done using two flavors of light quarks and with a series of $\\beta$ and $ma$ at the lattice size $24\\times12^{2}\\times6$. The calculation was done in the Taylar expansion formalism. We are able to calculate the first and second order derivatives of $\\langle\\bar{\\psi}\\psi\\rangle$ in both isoscalar and isovector channels. With the first derivatives being small, we find that the second derivatives are sizable close to the phase transition and the magnitude of $\\bar{\\psi}\\psi$ decreases under the influence of finite chemical potential in both channels.
Phase transition in finite density and temperature lattice QCD
Wang, Rui; Gong, Ming; Liu, Chuan; Liu, Yu-Bin; Liu, Zhao-Feng; Ma, Jian-Ping; Meng, Xiang-Fei; Zhang, Jian-Bo
2015-01-01T23:59:59.000Z
We investigate the behavior of the chiral condensate in lattice QCD at finite temperature and finite chemical potential. The study was done using two flavors of light quarks and with a series of $\\beta$ and $ma$ at the lattice size $24\\times12^{2}\\times6$. The calculation was done in the Taylar expansion formalism. We are able to calculate the first and second order derivatives of $\\langle\\bar{\\psi}\\psi\\rangle$ in both isoscalar and isovector channels. With the first derivatives being small, we find that the second derivatives are sizable close to the phase transition and the magnitude of $\\bar{\\psi}\\psi$ decreases under the influence of finite chemical potential in both channels.
Rare $B$ decays using lattice QCD form factors
Horgan, R R; Meinel, S; Wingate, M
2015-01-01T23:59:59.000Z
In this write-up we review and update our recent lattice QCD calculation of $B \\to K^*$, $B_s \\to \\phi$, and $B_s \\to K^*$ form factors [arXiv:1310.3722]. These unquenched calculations, performed in the low-recoil kinematic regime, provide a significant improvement over the use of extrapolated light cone sum rule results. The fits presented here include further kinematic constraints and estimates of additional correlations between the different form factor shape parameters. We use these form factors along with Standard Model determinations of Wilson coefficients to give Standard Model predictions for several observables [arXiv:1310.3887]. The modest improvements to the form factor fits lead to improved determinations of $F_L$, the fraction of longitudinally polarized vector mesons, but have little effect on most other observables.
Rare $B$ decays using lattice QCD form factors
R. R. Horgan; Z. Liu; S. Meinel; M. Wingate
2015-03-20T23:59:59.000Z
In this write-up we review and update our recent lattice QCD calculation of $B \\to K^*$, $B_s \\to \\phi$, and $B_s \\to K^*$ form factors [arXiv:1310.3722]. These unquenched calculations, performed in the low-recoil kinematic regime, provide a significant improvement over the use of extrapolated light cone sum rule results. The fits presented here include further kinematic constraints and estimates of additional correlations between the different form factor shape parameters. We use these form factors along with Standard Model determinations of Wilson coefficients to give Standard Model predictions for several observables [arXiv:1310.3887]. The modest improvements to the form factor fits lead to improved determinations of $F_L$, the fraction of longitudinally polarized vector mesons, but have little effect on most other observables.
Matching NLO QCD computations and parton shower simulations
S. Frixione; B. R. Webber
2002-07-12T23:59:59.000Z
We propose a method for matching the next-to-leading order (NLO) calculation of a given QCD process with a parton shower Monte Carlo (MC) simulation. The method has the following features: fully exclusive events are generated, with hadronization according to the MC model; total exclusive rates are accurate to NLO; NLO results for distributions are recovered upon expansion in $\\alpha_S$; hard emissions are treated as in NLO computations while soft/collinear emissions are handled by the MC simulation, with the same logarithmic accuracy as the MC; and matching between the hard- and soft/collinear-emission regions is smooth. A fraction of events with negative weight is generated, but unweighting remains possible with reasonable efficiency. The method is clarified using a simple toy model, and illustrated by application to the hadroproduction of W$^+$W$^-$ pairs.
QCD thermodynamics with continuum extrapolated Wilson fermions II
Szabolcs Borsanyi; Stephan Durr; Zoltan Fodor; Christian Holbling; Sandor D. Katz; Stefan Krieg; Daniel Nogradi; Kalman K. Szabo; Balint C. Toth; Norbert Trombitas
2015-04-14T23:59:59.000Z
We continue our investigation of 2+1 flavor QCD thermodynamics using dynamical Wilson fermions in the fixed scale approach. Two additional pion masses, approximately 440 MeV and 285 MeV, are added to our previous work at 545 MeV. The simulations were performed at 3 or 4 lattice spacings at each pion mass. The renormalized chiral condensate, strange quark number susceptibility and Polyakov loop is obtained as a function of the temperature and we observe a decrease in the light chiral pseudo-critical temperature as the pion mass is lowered while the pseudo-critical temperature associated with the strange quark number susceptibility or the Polyakov loop is only mildly sensitive to the pion mass. These findings are in agreement with previous continuum results obtained in the staggered formulation.
Improved Actions for QCD Thermodynamics on the Lattice
B. Beinlich; F. Karsch; E. Laermann
1995-10-18T23:59:59.000Z
Finite cut-off effects strongly influence the thermodynamics of lattice regularized QCD at high temperature in the standard Wilson formulation. We analyze the reduction of finite cut-off effects in formulations of the thermodynamics of $SU(N)$ gauge theories with three different $O(a^2)$ and $O(a^4)$ improved actions. We calculate the energy density and pressure on finite lattices in leading order weak coupling perturbation theory ($T\\rightarrow \\infty$) and perform Monte Carlo simulations with improved $SU(3)$ actions at non-zero $g^2$. Already on lattices with temporal extent $N_\\tau=4$ we find a strong reduction of finite cut-off effects in the high temperature limit, which persists also down to temperatures a few times the deconfinement transition temperature.
Giulio Chiribella; Giacomo Mauro D'Ariano; Paolo Perinotti
2007-12-09T23:59:59.000Z
We present a method for optimizing quantum circuits architecture. The method is based on the notion of "quantum comb", which describes a circuit board in which one can insert variable subcircuits. The method allows one to efficiently address novel kinds of quantum information processing tasks, such as storing-retrieving, and cloning of channels.
Randall Espinoza; Tom Imbo; Paul Lopata
2004-03-30T23:59:59.000Z
We investigate an entangled deformation of the deterministic quantum cloning process, called enscription, that can be applied to (certain) sets of distinct quantum states which are not necessarily orthogonal, called texts. Some basic theorems on enscribable texts are given, and a relationship to probabilistic quantum cloning is demonstrated.