QCD thermodynamics with an improved lattice action (original) (raw)

Lattice QCD thermodynamic results with improved staggered fermions

European Physical Journal C Particles and Fields, 2009

We present results on the QCD equation of state, obtained with two different improved dynamical staggered fermion actions and almost physical quark masses. Lattice cut-off effects are discussed in detail as results for three different lattice spacings are available now, i.e. results have been obtained on lattices with temporal extent of N τ =4,6 and 8. Furthermore we discuss the Taylor expansion approach to non-zero baryon chemical potential and present the isentropic equation of state on lines of constant entropy per baryon number.

QCD thermodynamics with Wilson fermions

2011

QCD is investigated at finite temperature using Wilson fermions in the fixed scale approach. A 2+1 flavor stout and clover improved action is used at four lattice spacings allowing for control over discretization errors. The light quark masses in this first study are fixed to heavier than physical values. The renormalized chiral condensate, quark number susceptibility and the Polyakov loop is measured and the results are compared with the staggered formulation in the fixed N t approach. The Wilson results at the finest lattice spacing agree with the staggered results at the highest N t .

Recent results on QCD thermodynamics: lattice QCD versus Hadron Resonance Gas model

Nuclear Physics A, 2011

We present our most recent investigations on the QCD cross-over transition temperatures with 2+1 staggered flavours and one-link stout improvement [JHEP 1009[JHEP :073, 2010. We extend our previous two studies [Phys. Lett. B643 (2006) 46, JHEP 0906:088 (2009)] by choosing even finer lattices (N t =16) and we work again with physical quark masses. All these results are confronted with the predictions of the Hadron Resonance Gas model and Chiral Perturbation Theory for temperatures below the transition region. Our results can be reproduced by using the physical spectrum in these analytic calculations. A comparison with the results of the hotQCD collaboration is also discussed.

Lattice QCD thermodynamics in the presence of the charm quark

Nuclear Physics A, 2013

In order to perform a continuum extrapolation for the trace anomaly, defined as I(T ) = T ∂(p/T 4 )/∂T , we interpolate the results for the four available lattice spacings, corresponding to N t = 6, 8, 10, 12 by means of a standard cubic spline ansatz. Notice that, with respect to our previous publication [10], a new set of N t = 12 points has been obtained, thereby making a spline interpolation possible. One high-precision point at N t = 16 has been simulated as a further check. We then varied the details of the spline interpolation to account for the statistical 2. Continuum estimate for the N f = 2 + 1 EOS

Lattice QCD thermodynamics on the Grid

Computer Physics Communications, 2010

We describe how we have used simultaneously O(10 3) nodes of the EGEE Grid, accumulating ca. 300 CPU-years in 2-3 months, to determine an important property of Quantum Chromodynamics. We explain how Grid resources were exploited eciently and with ease, using userlevel overlay based on Ganga and DIANE tools above standard Grid software stack. Application-specic scheduling and resource selection based on simple but powerful heuristics allowed to improve eciency of the processing to obtain desired scientic results by a specied deadline. This is also a demonstration of combined use of supercomputers, to calculate the initial state of the QCD system, and Grids, to perform the subsequent massively distributed simulations. The QCD simulation was performed on a 16 3 × 4 lattice. Keeping the strange quark mass at its physical value, we reduced the masses of the up and down quarks until, under an increase of temperature, the system underwent a second-order phase transition to a quark-gluon plasma. Then we measured the response of this system to an increase in the quark density. We nd that the transition is smoothened rather than sharpened. If conrmed on a ner lattice, this nding makes it unlikely for ongoing experimental searches to nd a QCD critical point at small chemical potential.

Heavy Quark Potential in Lattice QCD at Finite Temperature

Quark Confinement and the Hadron Spectrum V, 2003

Results of the study of lattice QCD with two flavors of nonperturbatively improved Wilson fermions at finite temperature are presented. The transition temperature for mπ mρ ∼ 0.8 and lattice spacing a ∼ 0.12 fm is determined. A two-exponent ansatz is successfully applied to describe the heavy quark potential in the confinement phase. * Talk given by V. Bornyakov at "

Free energies of heavy quarks in full-QCD lattice simulations with Wilson-type quark action

Nuclear Physics A, 2009

The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature in lattice QCD with 2+1 flavors of improved Wilson quarks. From the simulations on 32 3 × 12, 10, 8, 6, 4 lattices in the high temperature phase, based on the fixed scale approach, we find that, the heavy-quark free energies at short distance converge to the heavy-quark potential evaluated from the Wilson loop at zero temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the heavy-quark free energies approach to twice the single-quark free energies, implying that the interaction between heavy quarks is screened. The Debye screening mass obtained from the long range behavior of the free energy is compared with the results of thermal perturbation theory.

Mott-hadron resonance gas and lattice QCD thermodynamics

Physics of Particles and Nuclei, 2015

We present an effective model for the generic behaviour of hadron masses and phase shifts at finite temperature which shares basic features with recent developments within the PNJL model for correlations in quark matter. On this basis we obtain the transition between a hadron resonance gas phase and the quark gluon plasma in the spirit of the generalized Beth-Uhlenbeck approach where the Mott dissociation of hadrons is encoded in the hadronic phase shifts. Here we restrict ourselves to low-lying hadronic channels and perform a discussion of recent lattice QCD thermodynamics results from this perspective. We find agreement in the asymptotic regions while for the description of the transition itself the inclusion of further hadronic channels as well as a selfconsistent determination of the continuum thresholds is required.

Thermodynamics and heavy quark potential inNf = 2 dynamical QCD

Nuclear Physics B - Proceedings Supplements, 2003

We study N f = 2 lattice QCD with nonperturbatively improved Wilson fermions at finite temperature on 16 3 ·8 lattices. We determine the transition temperature at mπ mρ ∼ 0.8 and lattice spacing as small as a ∼ 0.12fm. The string breaking at T < Tc is also studied. We find that the static potential can be fitted by a simple expression involving string model potential at finite temperature.