315 research outputs found
Photon emission in Pb+Pb collisions at SpS and LHC
Yield of direct photons in Pb+Pb collisions at SpS and LHC energy is
evaluated with emphasis on estimate of possible uncertainty. Possibility of
experimental observation of direct photons at LHC is discussed. Predictions of
several models at SpS energy are compared with experimental data.Comment: 19 pages, 13 figure
Direct emission of light mesons from quark-gluon plasma surface
On the basis of hydrodynamic model of evolution of heavy ion collision we
consider emission of mesons directly from the
surface of quark-gluon plasma, with accounting of their absorption by
surrounding plasma hadronic gas. We evaluate upper and lower limits on yields
of these direct mesons in Pb+Pb collision at 158 AGeV (SpS) and 3150+3150 AGeV
(LHC), and find, that even in the case of the lowest yield, direct and
heavier mesons dominate at LHC energy at soft (). This
enhancement of the low meson production can be considered as a
quark-gluon plasma signature.Comment: Submitted to PR
Thermal Radiation from Au + Au Collisions at \sqrt{s} = 200 GEV/A Energy
The transverse momentum distribution of the direct photons measured by the
PHENIX collaboration in collisions at GeV/A has been
analyzed. It has been shown that the data can be reproduced reasonably well
assuming a deconfined state of thermalized quarks and gluons with initial
temperature more than the transition temperature for deconfinement inferred
from lattice QCD. The value of the initial temperature depends on the equation
of state of the evolving matter. The sensitivities of the results on various
input parameters have been studied. The effects of the modifications of
hadronic properties at non-zero temperature have been discussed.Comment: minor modifications in the text, accepted for publicatio
1+1 Dimensional Hydrodynamics for High-energy Heavy-ion Collisions
A 1+1 dimensional hydrodynamical model in the light-cone coordinates is used
to describe central heavy-ion collisions at ultrarelativistic bombarding
energies. Deviations from Bjorken's scaling are taken into account by choosing
finite-size profiles for the initial energy density. The sensitivity of fluid
dynamical evolution to the equation of state and the parameters of initial
state is investigated. Experimental constraints on the total energy of produced
particles are used to reduce the number of model parameters. Spectra of
secondary particles are calculated assuming that the transition from the
hydrodynamical stage to the collisionless expansion of matter occurs at a
certain freeze-out temperature. An important role of resonances in the
formation of observed hadronic spectra is demonstrated. The calculated rapidity
distributions of pions, kaons and antiprotons in central Au+Au collisions at
the c.m. energy 200 GeV per NN pair are compared with experimental data of the
BRAHMS Collaboration. Parameters of the initial state are reconstructed for
different choices of the equation of state. The best fit of these data is
obtained for a soft equation of state and Gaussian-like initial profiles of the
energy density, intermediate between the Landau and Bjorken limits.Comment: 43 pages, 27 figure
Quark-Gluon Matter
A concise review of the experimental and phenomenological progress in
high-energy heavy-ion physics over the past few years is presented. Emphasis is
put on measurements at BNL-RHIC and CERN-SPS which provide information on
fundamental properties of QCD matter at extreme values of temperature, density
and low-x. The new opportunities accessible at the LHC, which may help clarify
some of the current open issues, are also outlined.Comment: Minor changes to text. New refs. included. Updated figures with final
dat
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