7,946 research outputs found
Is there a flavor hierarchy in the deconfinement transition of QCD?
We present possible indications for flavor separation during the QCD
crossover transition based on continuum extrapolated lattice QCD calculations
of higher order susceptibilities. We base our findings on flavor specific
quantities in the light and strange quark sector. We propose a possible
experimental verification of our prediction, based on the measurement of higher
order moments of identified particle multiplicities. Since all our calculations
are performed at zero baryochemical potential, these results are of particular
relevance for the heavy ion program at the LHC.Comment: 5 pages, 3 figures, revte
A PNJL model in 0+1 Dimensions
We formulate the Polyakov-Nambu-Jona-Lasinio (PNJL) model in 0+1 dimensions.
The thermodynamics captured by the partition function yields a bulk pressure,
as well as quark susceptibilities versus temperature that are similar to the
ones in 3+1 dimensions. Around the transition temperature the behavior in the
pressure and quark susceptibilities follows from the interplay between the
lowest Matsubara frequency and the Polyakov line. The reduction to the lowest
Matsubara frequency yields a matrix Model. In the presence of the Polyakov line
the UV part of the Dirac spectrum features oscillations when close to the
transition temperature.Comment: 18 pages, 13 figure
Freeze-out parameters: lattice meets experiment
We present our results for ratios of higher order fluctuations of electric
charge as functions of the temperature. These results are obtained in a system
of 2+1 quark flavors at physical quark masses and continuum extrapolated. We
compare them to preliminary data on higher order moments of the net electric
charge distribution from the STAR collaboration. This allows us to determine
the freeze-out temperature and chemical potential from first principles. We
also show continuum-extrapolated results for ratios of higher order
fluctuations of baryon number. These will allow to test the consistency of the
approach, by comparing them to the corresponding experimental data (once they
become available) and thus extracting the freeze-out parameters in an
independent way.Comment: 5 pages, 7 figures, revte
Freeze-out parameters from electric charge and baryon number fluctuations: is there consistency?
Recent results for moments of multiplicity distributions of net-protons and
net-electric charge from the STAR collaboration are compared to lattice QCD
results for higher order fluctuations of baryon number and electric charge by
the Wuppertal-Budapest collaboration, with the purpose of extracting the
freeze-out temperature and chemical potential. All lattice simulations are
performed for a system of 2+1 dynamical quark flavors, at the physical mass for
light and strange quarks; all results are continuum extrapolated. We show that
it is possible to extract an upper value for the freeze-out temperature, as
well as precise baryo-chemical potential values corresponding to the four
highest collision energies of the experimental beam energy scan. Consistency
between the freeze-out parameters obtained from baryon number and electric
charge fluctuations is found. The freeze-out chemical potentials are now in
agreement with the statistical hadronization model.Comment: 5 pages, 4 figures, references added, discussion added to the
introduction, results unchange
An effective thermodynamic potential from the instanton with Polyakov-loop contributions
We derive an effective thermodynamic potential (Omega_eff) at finite
temperature (T>0) and zero quark-chemical potential (mu_R=0), using the
singular-gauge instanton solution and Matsubara formula for N_c=3 and N_f=2 in
the chiral limit. The momentum-dependent constituent-quark mass is also
obtained as a function of T, employing the Harrington-Shepard caloron solution
in the large-N_c limit. In addition, we take into account the imaginary quark
chemical potential mu_I = A_4, translated as the traced Polayakov-loop (Phi) as
an order parameter for the Z(N_c) symmsetry, characterizing the confinement
(intact) and deconfinement (spontaneously broken) phases. As a result, we
observe the crossover of the chiral (chi) order parameter sigma^2 and Phi. It
also turns out that the critical temperature for the deconfinment phase
transition, T^Z_c is lowered by about (5-10)% in comparison to the case with a
constant constituent-quark mass. This behavior can be understood by
considerable effects from the partial chiral restoration and nontrivial QCD
vacuum on Phi. Numerical calculations show that the crossover transitions occur
at (T^chi_c,T^Z_c) ~ (216,227) MeV.Comment: 15 pages, 7 figure
Fluctuations and correlations in high temperature QCD
We calculate second- and fourth-order cumulants of conserved charges in a
temperature range stretching from the QCD transition region towards the realm
of (resummed) perturbation theory. We perform lattice simulations with
staggered quarks; the continuum extrapolation is based on in
the crossover-region and at higher temperatures. We find that
the Hadron Resonance Gas model predictions describe the lattice data rather
well in the confined phase. At high temperatures (above 250 MeV) we find
agreement with the three-loop Hard Thermal Loop results.Comment: 18 pages revtex, 13 figure
QCD transition temperature: full staggered result
We conclude our investigations on the QCD cross-over transition temperatures
with 2+1 staggered flavours and one-link stout improvement. 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. These new results [for details see JHEP 1009:073,2010] support our
earlier findings. We compare them with the published results of the hotQCD
collaboration. 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. The findings of the hotQCD collaboration can be recovered
only by using a distorted spectrum. This analysis provides a simple explanation
for the observed discrepancy in the transition T between our and the hotQCD
collaborations.Comment: presented at the XXVIII. International Symposium on Lattice Field
Theory, June 14-19,2010, Villasimius, Sardinia Ital
Recent results on the Equation of State of QCD
We report on a continuum extrapolated result (arXiv:1309.5258) for the
equation of state (EoS) of QCD with dynamical quark flavors and
discuss preliminary results obtained with an additional dynamical charm quark
(). For all our final results, the systematics are controlled, quark
masses are set to their physical values, and the continuum limit is taken using
at least three lattice spacings corresponding to temporal extents up to
.Comment: Conference proceedings: The 32nd International Symposium on Lattice
Field Theory - Lattice 2014, June 23-28, 2014, Columbia University, New York,
New Yor
The QCD phase diagram from analytic continuation
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 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 10, 12 and 16 lattices. By combining the analysis for these
three observables we find, for the curvature, the value .Comment: 14 pages, 4 figures, revised versio
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