2,842 research outputs found
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
Continuum EoS for QCD with Nf=2+1 flavors
We report on a continuum extrapolated result [arXiv:1309.5258] for the
equation of state (EoS) of QCD with dynamical quark flavors. In this
study, all 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 . A Symanzik improved gauge and
stout-link improved staggered fermion action is used. Our results are available
online [ancillary file to arXiv:1309.5258].Comment: Conference proceedings, 7 pages, 4 figures. Talk presented at 31st
International Symposium on Lattice Field Theory (LATTICE 2013), July 29 -
August 3, 2013, Mainz, German
Dynamical overlap simulations using HMC
We apply the Hybrid Monte Carlo method to the simulation of overlap fermions.
We give the fermionic force for the molecular dynamics update. We present early
results on a small dynamical chiral ensemble.Comment: Lattice2004(machines), 3 pages; references updated, minor changes to
tex
QCD thermodynamics with dynamical overlap fermions
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.Comment: 14 pages, 6 figures, 1 tabl
Determination of SU(2) ChPT LECs from 2+1 flavor staggered lattice simulations
By fitting pion masses and decay constants from 2+1 flavor staggered lattice
simulations to the predictions of NLO and NNLO SU(2) chiral perturbation theory
we determine the low-energy constants l_3 and l_4. The lattice ensembles were
generated by the Wuppertal-Budapest collaboration and cover pion masses in the
range of 135 to 435 MeV and lattice scales between 0.7 and 2.0 GeV. By choosing
a suitable scaling trajectory, we were able to demonstrate that precise and
stable results for the LECs can be obtained from continuum ChPT to NLO. The
pion masses available in this work also allow us to study the applicability of
using ChPT to extrapolate from higher masses to the physical pion mass.Comment: 8 pages, 8 figures, 1 table, talk presented at Xth Quark Confinement
and the Hadron Spectrum, Munich, October 201
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
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