15 research outputs found
Meson correlators above deconfinement
We review recent progress in studying spectral functions for mesonic
observables at finite temperatures, by analysis of imaginary time correlators
directly calculated on isotropic lattices. Special attention is paid to the
lattice artifacts present in such calculations.Comment: Latex, 3 figures uses iopart.cls, talk presented at Hot Quarks 2004,
July 18-24, 2004, Taos Valley New Mexico, US
Hadron correlators, spectral functions and thermal dilepton rates from lattice QCD
We discuss information on thermal modifications of hadron properties which
can be extracted from the structure of Euclidean correlation functions of
hadronic currents as well as more direct information obtained through the
reconstruction of the spectral functions based on the Maximum Entropy Method.Comment: 4 pages, latex2e, 5 EPS-files, invited contribution to the 16th Int.
Conf. on Ultra-Relativistic Nucleus-Nucleus Collisions, Nantes, France, 18 -
24 July, 200
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
Behavior of Charmonium Systems after Deconfinement
We present a study of charmonia in hot gluonic plasma, for temperatures upto
three times the deconfinement transition temperature Tc. q \bar{q} systems with
quark masses close to the charm mass and different spin-parity quantum numbers
were studied on very fine isotropic lattices. The analysis of temporal
correlators, and spectral functions constructed from them, shows that the J/psi
and eta_c survive up to quite high temperatures, with little observable change
up to 1.5 Tc, and then gradually weakening and disappearing by 3 Tc. For the
scalar and axial vector channels, serious modifications are induced by the hot
medium already close to Tc, possibly dissociating the mesons by 1.1 Tc.Comment: 18 pages, 31 eps figure
Elliptical Flow in Relativistic Ion Collisions at s^(1/2)= 200 A GeV
A consistent picture of the Au+Au and D+Au, s^1/2 = 200 A GeV measurements at
RHIC obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors including both
the rapidity and transverse momentum spectra was previously developed with the
simulation LUCIFER. The approach was modeled on the early production of a fluid
of pre-hadrons after the completion of an initial, phase of high energy
interactions. The formation of pre-hadrons is discussed here, in a perturbative
QCD approach as advocated by Kopeliovich, Nemchik and Schmidt. In the second
phase of LUCIFER, a considerably lower energy hadron-like cascade ensues. Since
the dominant collisions occurring in this latter phase are meson-meson in
character while the initial collisions are between baryons, i.e. both involve
hadron sized interaction cross-sections, there is good reason to suspect that
the observed elliptical flow will be produced naturally, and this is indeed
found to be the case.Comment: 7 pages, 6 figure
Lattice calculations of meson correlators and spectral functions at finite temperature
I review recent progress in relating meson spectral function to imaginary
time correlation function at finite temperature calculated on isotropic as well
as on anisotropic lattices. Special attention is payed for the lattice
artifacts present in calculation of meson spectral functions. Results in the
case of light quarks as well as heavy quarks are reviewed which indicate in
particular that even in the chiral limit meson spectral functions have
non-trivial structure and the ground state quarkonia survive up to temperature
1.5T_cComment: Invited plenary talk presented at SQM03 (Atlantic Beach, March 12-17,
2003), 10 pages LaTeX, uses iopams.sty, iopart.cl
News from Lattice QCD on Heavy Quark Potentials and Spectral Functions of Heavy Quark States
We discuss recent lattice results on in-medium properties of hadrons and
focus on thermal properties of heavy quark bound states. We will clarify the
relation between heavy quark free energies and potentials used to analyze the
melting of heavy quark bound states. Furthermore, we present calculations of
meson spectral functions which indicate that the charmonium ground states,
J/psi and eta_c, persist in the quark gluon plasma as well defined resonances
with no significant change of their zero temperature masses at least up to T ~
1.5 T_c. We also briefly comment on the current status of lattice calculations
at non-vanishing baryon number density.Comment: Plenary talk at the 17th International Conference on Ultra
Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland,
California, 11-17 Jan 2004. Submitted to J.Phys.
Suppression of High Transverse Momentum Spectra in Au+Au Collisions at RHIC
Au+Au, A GeV measurements at RHIC, obtained with the PHENIX,
STAR, PHOBOS and BRAHMS detectors, have all indicated a suppression of neutral
pion production, relative to an appropriately normalized NN level. For central
collisions and vanishing pseudo-rapidity these experiments exhibit suppression
in charged meson production, especially at medium to large transverse momenta.
In the PHENIX experiment similar behavior has been reported for
spectra.
In a recent work on the simpler D+Au interaction, to be considered perhaps as
a tune-up for Au+Au, we reported on a pre-hadronic cascade mechanism which
explains the mixed observation of moderately reduced suppression at
higher pseudo-rapidity as well as the Cronin enhancement at mid-rapidity. Here
we present the extension of this work to the more massive ion-ion collisions.
Our major thesis is that much of the suppression is generated in a late stage
cascade of colourless pre-hadrons produced after an initial short-lived
coloured phase. We present a pQCD argument to justify this approach and to
estimate the time duration of this initial phase. Of essential
importance is the brevity in time of the coloured phase existence relative to
that of the strongly interacting pre-hadron phase. The split into two phases is
of course not sharp in time, but adequate for treating the suppression of
moderate and high mesons.Comment: 19 pages, 10 figure
A study of charmonium systems across the deconfinement transition
We present results from lattice studies of charmonium systems near the deconfinement transition temperature. On quenched isotropic lattices with lattice spacings between 0.02 and 0.05 fm, qq systems with quark masses close to the charm mass and with different spin-parity quantum numbers are studied in the temperature range 0.9T_c-3T_c. Results for temporal correlators of local operators, and the spectral functions constructed from them, are discussed. For the pseudoscalar and vector channels, the correlators are observed to change very little across the deconfinement transition, unlike in the case of the light quarks. (orig.)Available from TIB Hannover: RA 2999(02-108) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
Hadron correlators, spectral functions and thermal dilepton rates from lattice QCD
We discuss information on thermal modifications of hadron properties which can be extracted from the structure of Euclidean correlation functions of hadronic currents as well as more direct information obtained through the reconstruction of the spectral functions based on the Maximum Entropy Method. (orig.)Available from TIB Hannover: RA 2999(02-153) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman