1,599 research outputs found
Hadronic fluctuations in the QGP
We analyze fluctuations of quark number and electric charge, in 2-flavour QCD
at finite temperature and vanishing net baryon number density. In the hadronic
phase we find that an enhancement of charge fluctuations arises from
contributions of doubly charged hadrons to the thermodynamics. The rapid
suppression of fluctuations seen in the high temperature phase suggests that in
the QGP quark number and electric charge are predominantly carried by
quasi-particles with the quantum numbers of quarks.Comment: 4 pages, 6 EPS-files, talk presented at Quark Matter 2005, Budapes
Flavor and Quark Mass Dependence of QCD Thermodynamics
We calculate the transition temperature in 2 and 3-flavor QCD using improved
gauge and staggered fermion actions on lattices with temporal extent Nt=4. We
find Tc=173(8)MeV and 154(8)MeV for nf=2 and 3, respectively. In the case of
3-flavor QCD we present evidence that the chiral critical point, i.e. the
second order endpoint of the line of first order chiral phase transitions,
belongs to the universality class of the 3d Ising model.Comment: Talk given at Lattice 2000 (Finite Temperature), 4 pages, 6
EPS-figure
Charmonium at finite temperature
We study charmoinum correlators and spectral functions at finite temperature
within the quenched approximation using isotropic lattices with lattice spacing
a^-1=4.86 GeV and 9.72 GeV. Although we observe some medium modifications of
the ground state charmonium spectral function above deconfinement, we find that
ground state charmonia (J/psi and eta_c) exist in the deconfined phase at least
up to temperatures as high as 1.5Tc. P-wave charmonia (chi_c) on the other hand
are dissociated already at 1.12Tc.Comment: Contribution to Lattice 2003 (non-zero) LaTeX, 3 pages, 3 figures,
uses espcrc2 styl
Free Meson Spectral Functions on the Lattice
We present results from an analytic calculation of thermal meson spectral
functions in the infinite temperature (free field) limit. We compare spectral
functions for various lattice fermion formulations used at present in studies
of in-medium properties of hadrons based on the maximum entropy method (MEM).
In particular, we will present a new calculation of spectral functions
performed with extended quark sources.Comment: 3 pages, Lattice2003(nonzero
Resonant photonuclear isotope detection using medium-energy photon beam
Resonant photonuclear isotope detection (RPID) is a nondestructive
detection/assay of nuclear isotopes by measuring gamma rays following
photonuclear reaction products. Medium-energy wideband photons of 12-16 MeV are
used for the photonuclear reactions and gamma rays characteristic of the
reaction products are measured by means of high-sensitivity Ge detectors.
Impurities of stable and radioactive isotopes of the orders of micro-nano gr
and ppm-ppb are investigated. RPID is used to study nuclear isotopes of
astronuclear and particle physics interests and those of geological and
historical interests. It is used to identify radioactive isotopes of fission
products as well.Comment: 6 pages, 3 figure
Common features of deconfining and chiral critical points in QCD and the three state Potts model in an external field
In the presented study we investigated the second order endpoints of the
lines of first order phase transitions which emerge for the QCD in the heavy
and light quark mass regime and for the three-dimensional three state Potts
model with an external field. We located the endpoints with Binder cumulants
and constructed the energy-like and ordering field like observables. The joint
probability distributions of these scaling fields and the values of the Binder
cumulant confirm that all three endpoints belong to the universality class of
the 3-dimensional Ising model.Comment: Based on a poster presented by S.Stickan at the CCP2001 Aachen,4
pages,6 figures, to be published in computer physics communicatio
Fluctuations in the vicinity of the phase transition line for two flavor QCD
We study the susceptibilities of quark number, isospin number and electric
charge in numerical simulations of lattice QCD at high temperature and density.
We discuss the equation of state for 2 flavor QCD at non-zero temperature and
density. Derivatives of with respect to quark chemical potential
are calculated up to sixth order. From this Taylor series, the
susceptibilities are estimated as functions of temperature and .
Moreover, we comment on the hadron resonance gas model, which explains well our
simulation results below .Comment: 3 pages, 5 figures, Talk presented at Lattice2004(non-zero
Where is the chiral critical point in 3-flavor QCD?
We determine the location of the second order endpoint of the line of first
order chiral phase transition in 3-flavor QCD at vanishing chemical potential.
Using Ferrenberg-Swendsen reweighting for two values of the quark mass we
determine the dependence of the transition line on the chemical potential and
locate the chiral critical point. For both quantities we find a significant
quark mass dependence.Comment: 3 pages, Lattice2003(nonzero), one reference exchange
Infrared features of unquenched finite temperature lattice Landau gauge QCD
The color diagonal and color antisymmetric ghost propagators slightly above
of MILC lattices are measured and compared with
zero temperature unquenched MILC and MILC
lattices and zero temperature quenched and
6.45 lattices. The expectation value of the color antisymmetric ghost
propagator is zero but its Binder cumulant, which is consistent
with that of dimensional Gaussian distribution below , decreases
above . Although the color diagonal ghost propagator is temperature
independent, the norm of the color antisymmetric ghost propagator is
temperature dependent. The expectation value of the ghost condensate observed
at zero temperature unquenched configuration is consistent with 0 in .
We also measure transverse, magnetic and electric gluon propagator and
extract gluon screening masses. The running coupling measured from the product
of the gluon dressing function and the ghost dressing function are almost
temperature independent but the effect of condensate observed at zero
temperature is consistent with 0 in .
The transverse gluon dressing function at low temperature has a peak in the
infrared but it becomes flatter at high temperature. Its absolute value in the
high momentum is larger for high temperature and similar to the magnetic gluon
dressing function. The electric gluon propagator at high momentum is
temperature independent. These data imply that the magnetic gluon propagator
and the color antisymmetric ghost propagator are affected by the presence of
dynamical quarks and there are strong non-perturbative effects through the
temperature dependent color anti-symmetric ghost propagator.Comment: 11 pages 16 figures, version accepted for publication in Phys. Rev.
The QCD phase diagram: A comparison of lattice and hadron resonance gas model calculations
We compare the lattice results on QCD phase diagram for two and three flavors
with the hadron resonance gas model (HRGM) calculations. Lines of constant
energy density have been determined at different baryo-chemical
potentials . For the strangeness chemical potentials , we use two
models. In one model, we explicitly set for all temperatures and
baryo-chemical potentials. This assignment is used in lattice calculations. In
the other model, is calculated in dependence on and
according to the condition of vanishing strangeness. We also derive an
analytical expression for the dependence of on by applying
Taylor expansion of . In both cases, we compare HRGM results on
diagram with the lattice calculations. The agreement is excellent,
especially when the trigonometric function of is truncated up to the
same order as done in lattice simulations. For studying the efficiency of the
truncated Taylor expansion, we calculate the radius of convergence. For zero-
and second-order radii, the agreement with lattice is convincing. Furthermore,
we make predictions for QCD phase diagram for non-truncated expressions and
physical masses. These predictions are to be confirmed by heavy-ion experiments
and future lattice calculations with very small lattice spacing and physical
quark masses.Comment: 25 pages, 8 eps figure
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