268 research outputs found
On the magnetic equation of state in (2+1)-flavor QCD
A first study of critical behavior in the vicinity of the chiral phase
transition of (2+1)-flavor QCD is presented. We analyze the quark mass and
volume dependence of the chiral condensate and chiral susceptibilities in QCD
with two degenerate light quark masses and a strange quark. The strange quark
mass (m_s) is chosen close to its physical value; the two degenerate light
quark masses (m_l) are varied in a wide range 1/80 \le m_l/m_s \le 2/5, where
the smallest light quark mass value corresponds to a pseudo-scalar Goldstone
mass of about 75 MeV. All calculations are performed with staggered fermions on
lattices with temporal extent Nt=4. We show that numerical results are
consistent with O(N) scaling in the chiral limit. We find that in the region of
physical light quark mass values, m_l/m_s \simeq 1/20, the temperature and
quark mass dependence of the chiral condensate is already dominated by
universal properties of QCD that are encoded in the scaling function for the
chiral order parameter, the magnetic equation of state. We also provide
evidence for the influence of thermal fluctuations of Goldstone modes on the
chiral condensate at finite temperature. At temperatures below, but close to
the chiral phase transition at vanishing quark mass, this leads to a
characteristic dependence of the light quark chiral condensate on the square
root of the light quark mass.Comment: 18 pages, 18 EPS-file
Conserved Charge Fluctuations from Lattice QCD and the Beam Energy Scan
We discuss the next-to-leading order Taylor expansion of ratios of cumulants
of net-baryon number fluctuations. We focus on the relation between the
skewness ratio, , and the kurtosis ratio,
. We show that differences in these two
cumulant ratios are small for small values of the baryon chemical potential.
The next-to-leading order correction to however is
approximately three times larger than that for . The former thus
drops much more rapidly with increasing beam energy, . We argue
that these generic patterns are consistent with current data on cumulants of
net-proton number fluctuations measured by the STAR Collaboration at
~GeV.Comment: 4 pages, 4 figures, contribution to the Quark Matter 2015 proceeding
Charmonium properties in hot quenched lattice QCD
We study the properties of charmonium states at finite temperature in
quenched QCD on large and fine isotropic lattices. We perform a detailed
analysis of charmonium correlation and spectral functions both below and above
. Our analysis suggests that both S wave states ( and )
and P wave states ( and ) disappear already at about . The charm diffusion coefficient is estimated through the Kubo formula and
found to be compatible with zero below and approximately at
.Comment: 32 pages, 19 figures, typo corrected, discussions on isotropic vs
anisotropic lattices expanded, published versio
Study of the finite temperature transition in 3-flavor QCD using the R and RHMC algorithms
We study the finite temperature transition in QCD with three flavors of equal
masses using the R and RHMC algorithm on lattices with temporal extent
N_{\tau}=4 and 6. For the transition temperature in the continuum limit we find
r_0 T_c=0.429(8) for the light pseudo-scalar mass corresponding to the end
point of the 1st order transition region. When comparing the results obtained
with the R and RHMC algorithms for p4fat3 action we see no significant
step-size errors down to a lightest pseudo-scalar mass of m_{ps} r_0=0.4.Comment: 13 pages, RevTeX, 10 figure
Equation of State for physical quark masses
We calculate the QCD equation of state for temperatures corresponding to the
transition region with physical mass values for two degenerate light quark
flavors and a strange quark using an improved staggered fermion action
(p4-action) on lattices with temporal extent N_tau=8. We compare our results
with previous calculations performed at twice larger values of the light quark
masses as well as with results obtained from a resonance gas model calculation.
We also discuss the deconfining and chiral aspects of the QCD transition in
terms of renormalized Polyakov loop, strangeness fluctuations and subtracted
chiral condensate. We show that compared to the calculations performed at twice
larger value of the light quark mass the transition region shifts by about 5
MeV toward smaller temperaturesComment: 7 pages, LaTeX, 6 figures; minor corrections, typos corrected,
references adde
The Spatial String Tension and Dimensional Reduction in QCD
We calculate the spatial string tension in (2+1) flavor QCD with physical
strange quark mass and almost physical light quark masses using lattices with
temporal extent N_tau=4,6 and 8. We compare our results on the spatial string
tension with predictions of dimensionally reduced QCD. This suggests that also
in the presence of light dynamical quarks dimensional reduction works well down
to temperatures 1.5T_c.Comment: 8 pages ReVTeX, 4 figure
- …