656 research outputs found
Static pair free energy and screening masses from correlators of Polyakov loops: continuum extrapolated lattice results at the QCD physical point
We study the correlators of Polyakov loops, and the corresponding gauge
invariant free energy of a static quark-antiquark pair in 2+1 flavor QCD at
finite temperature. Our simulations were carried out on = 6, 8, 10, 12,
16 lattices using Symanzik improved gauge action and a stout improved staggered
action with physical quark masses. The free energies calculated from the
Polyakov loop correlators are extrapolated to the continuum limit. For the free
energies we use a two step renormalization procedure that only uses data at
finite temperature. We also measure correlators with definite Euclidean time
reversal and charge conjugation symmetry to extract two different screening
masses, one in the magnetic, and one in the electric sector, to distinguish two
different correlation lengths in the full Polyakov loop correlator
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
Static quark-antiquark pair free energy and screening masses: continuum results at the QCD physical point
We study the correlators of Polyakov loops, and the corresponding gauge
invariant free energy of a static quark-antiquark pair in 2+1 flavor QCD at
finite temperature. Our simulations were carried out on = 6, 8, 10, 12,
16 lattices using a Symanzik improved gauge action and a stout improved
staggered action with physical quark masses. The free energies calculated from
the Polyakov loop correlators are extrapolated to the continuum limit. For the
free energies we use a two step renormalization procedure that only uses data
at finite temperature. We also measure correlators with definite Euclidean time
reversal and charge conjugation symmetry to extract two different screening
masses, one in the magnetic, and one in the electric sector, to distinguish two
different correlation lengths in the full Polyakov loop correlator. This
conference contribution is based on the paper: JHEP 1504 (2015) 138Comment: 7 pages, 4 figures. Talk presented at the 33rd International
Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe
International Conference Center, Kobe, Japa
Probing the Structure of Jet Driven Core-Collapse Supernova and Long Gamma Ray Burst Progenitors with High Energy Neutrinos
Times of arrival of high energy neutrinos encode information about their
sources. We demonstrate that the energy-dependence of the onset time of
neutrino emission in advancing relativistic jets can be used to extract
important information about the supernova/gamma-ray burst progenitor structure.
We examine this energy and time dependence for different supernova and
gamma-ray burst progenitors, including red and blue supergiants, helium cores,
Wolf-Rayet stars, and chemically homogeneous stars, with a variety of masses
and metallicities. For choked jets, we calculate the cutoff of observable
neutrino energies depending on the radius at which the jet is stalled. Further,
we exhibit how such energy and time dependence may be used to identify and
differentiate between progenitors, with as few as one or two observed events,
under favorable conditions
SU(2) chiral perturbation theory low-energy constants from 2+1 flavor staggered lattice simulations
We extract the next-to-leading-order low-energy constants \bar\ell_3 and
\bar\ell_4 of SU(2) chiral perturbation theory, based on precise lattice data
for the pion mass and decay constant on ensembles generated by the
Wuppertal-Budapest Collaboration for QCD thermodynamics. These ensembles
feature 2+1 flavors of two-fold stout-smeared dynamical staggered fermions
combined with Symanzik glue, with pion masses varying from 135 to 435 MeV,
lattice scales between 0.7 and 2.0 GeV, while m_s is kept fixed at its physical
value. Moderate taste splittings and the scale being set through the pion decay
constant allow us to restrict ourselves to the taste pseudoscalar state and to
use formulas from continuum chiral perturbation theory. Finally, by dropping
the data points near 135 MeV from the fits, we can explore the range of pion
masses that is needed in SU(2) chiral perturbation theory to reliably
extrapolate to the physical point.Comment: 40 pages, 22 figures, 3 tables; v2: expanded discussion, matches
published versio
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
The QCD equation of state and the effects of the charm
We present an update on the QCD equation of state of the Wuppertal-Budapest
Collaboration, extending our previous studies [JHEP 0601 (2006) 089, JHEP 1011
(2010) 077]. A Symanzik improved gauge and a stout-link improved staggered
fermion action is utilized. We discuss partial quenching and present
preliminary results for the fully dynamical charmed equation of state.Comment: Talk presented at the XXIX International Symposium on Lattice Field
Theory, July 10-16, 2011, Lake Tahoe, Californi
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