1,431 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

### The H dibaryon on the lattice

We present our final results for the mass of the six quark flavor singlet
state (J^P=0^+, S=-2) called H dibaryon, which would be the lightest possible
strangelet in the context of strange quark matter. The calculations are
performed in quenched QCD on (8-24)^3 x 30 lattices with the (1,2) Symanzik
improved gauge action and the clover fermion action. Furthermore the fuzzing
technique for the fermion fields and smearing of the gauge fields is applied in
order to enhance the overlap with the ground state. Depending on the lattice
size we observe an H mass slightly above or comparable with the \Lambda\Lambda
threshold for strong decay. Therefore a bound H dibaryon state seemed to be
ruled out by our simulation.Comment: Lattice2002(spectrum), 3 pages, 2 figures, Proceedings of the XX
International Symposium on Lattice Field Theory, June 24-29, 2002 (MIT,
Cambridge, USA

### Testing MEM with Diquark and thermal Meson Correlation Functions

When applying the maximum entropy method (MEM) to the analysis of hadron
correlation functions in QCD a central issue is to understand to what extent
this method can distinguish bound states, resonances and continuum
contributions to spectral functions. We discuss these issues by analyzing meson
and diquark correlation functions at zero temperature as well as free quark
anti-quark correlators. The latter test the applicability of MEM to high
temperature QCD.Comment: 6 pages, 6 figures. Contribution to the proceedings of the Conference
on Strong and Electroweak Matter (SEWM 2000), Marseille, France, 14-17 June
2000; Figure 3(b) change

### Thermodynamics and in-medium hadron properties from lattice QCD

Non-perturbative studies of the thermodynamics of strongly interacting
elementary particles within the context of lattice regularized QCD are being
reviewed. After a short introduction into thermal QCD on the lattice we report
on the present status of investigations of bulk properties. In particular, we
discuss the present knowledge of the phase diagram including recent
developments of QCD at non-zero baryon number density. We continue with the
results obtained so far for the transition temperature as well as the
temperature dependence of energy and pressure and comment on screening and the
heavy quark free energies. A major section is devoted to the discussion of
thermal modifications of hadron properties, taking special account of recent
progress through the use of the maximum entropy method.Comment: prepared for "Quark-Gluon Plasma III", R.Hwa (ed.

### 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

### 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

### Thermodynamics of two-colour QCD

We discuss the thermodynamics of two-colour QCD with four flavours of
staggered quarks on 8^3x4 and 16^3x4 lattices. In our simulations we use the
Naik action for the fermions and a (1,2) tree-level improved gauge action. We
analyze the deconfinement and chiral phase transitions for four different quark
masses (m=0.1,0.05,0.025,0.015). Contrary to three-colour QCD the peak in the
Polyakov loop susceptibility decreases with decreasing quark mass. This
reflects an early breaking of the string in the heavy quark potential, which we
verify explicitly by calculating the heavy quark potential at finite
temperature using Polyakov loop correlations.Comment: LATTICE98(hightemp), 3 pages, LaTeX2e File, 5 EPS-figures,
espcrc2.st

### Infrared features of unquenched finite temperature lattice Landau gauge QCD

The color diagonal and color antisymmetric ghost propagators slightly above
$T_c$ of $N_f=2$ MILC $24^3\times 12$ lattices are measured and compared with
zero temperature unquenched $N_f=2+1$ MILC$_c$ $20^3\times 64$ and MILC$_f$
$28^3\times 96$ lattices and zero temperature quenched $56^4$ $\beta=6.4$ and
6.45 lattices. The expectation value of the color antisymmetric ghost
propagator $\phi^c(q)$ is zero but its Binder cumulant, which is consistent
with that of $N_c^2-1$ dimensional Gaussian distribution below $T_c$, decreases
above $T_c$. Although the color diagonal ghost propagator is temperature
independent, the $l^1$ 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 $T>T_c$.
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 $A^2$ condensate observed at zero
temperature is consistent with 0 in $T>T_c$.
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.

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