501 research outputs found
Quasi-particle model for deconfined matter
Our quasi-particle model for deconfined matter near T_c is reviewed. The
extrapolation of lattice QCD data to a finite baryo-chemical potential is
discussed. Determined by the chiral transition temperature T_c, the resulting
equation of state of neutral and beta-stable deconfined matter is soft and
limits size and mass of pure quark stars.Comment: Contribution to 5th Intern. Conf. "Quark Confinement and the Hadron
Spectrum", Gargnano (It), Sep. 10 - 14, 200
Pion interferometry at RHIC: probing a thermalized quark-gluon-plasma?
We calculate the Gaussian radius parameters of the pion-emitting source in high energy heavy ion collisions, assuming a first order phase transition from a thermalized Quark-Gluon-Plasma (QGP) to a gas of hadrons. Such a model leads to a very long-lived dissipative hadronic rescattering phase which dominates the properties of the two-pion correlation functions. The radii are found to depend only weakly on the thermalization time tau i, the critical temperature T c (and thus the latent heat), and the specific entropy of the QGP. The dissipative hadronic stage enforces large variations of the pion emission times around the mean. Therefore, the model calculations suggest a rapid increase of R out/R side as a function of K T if a thermalized QGP were formed
The Disappearance of Flow
We investigate the disappearance of collective flow in the reaction plane in
heavy-ion collisions within a microscopic model (QMD). A systematic study of
the impact parameter dependence is performed for the system Ca+Ca. The balance
energy strongly increases with impact parameter. Momentum dependent
interactions reduce the balance energies for intermediate impact parameters
fm. Dynamical negative flow is not visible in the laboratory
frame but does exist in the contact frame for the heavy system Au+Au. For
semi-peripheral collisions of Ca+Ca with fm a new two-component
flow is discussed. Azimuthal distributions exhibit strong collectiv flow
signals, even at the balance energy.Comment: 19 pages, 7 eps-figures, uses psfig.sty; complete postscript file
available at
ftp://th.physik.uni-frankfurt.de/pub/bass/GSI-preprint_95-11.ps.
Particle Correlations at RHIC - Scrutiny of a Puzzle
We present calculations of two-pion and two-kaon correlation functions in
relativistic heavy ion collisions from a relativistic transport model that
includes explicitly a first-order phase transition from a thermalized
quark-gluon plasma to a hadron gas. We compare the obtained correlation radii
with recent data from RHIC. The predicted R_side radii agree with data while
the R_out and R_long radii are overestimated. We also address the impact of
in-medium modifications, for example, a broadening of the rho-meson, on the
correlation radii. In particular, the longitudinal correlation radius R_long is
reduced, improving the comparison to data.Comment: 4 pages, 3 figure
Kaon interferometry : a sensitive probe of the QCD equation of state?
We calculate the kaon HBT radius parameters for high energy heavy ion collisions, assuming a first order phase transition from a thermalized Quark-Gluon-Plasma to a gas of hadrons. At high transverse momenta K_T ~ 1 GeV/c direct emission from the phase boundary becomes important, the emission duration signal, i.e., the R_out/R_side ratio, and its sensitivity to T_c (and thus to the latent heat of the phase transition) are enlarged. Moreover, the QGP+hadronic rescattering transport model calculations do not yield unusual large radii (R_i<9fm). Finite momentum resolution effects have a strong impact on the extracted HBT parameters (R_i and lambda) as well as on the ratio R_out/R_side
Kaon Interferometry: A Sensitive Probe of the QCD Equation of State?
We calculate the kaon HBT radius parameters for high energy heavy ion
collisions, assuming a first order phase transition from a thermalized
Quark-Gluon-Plasma to a gas of hadrons. At high transverse momenta K_T ~ 1
GeV/c direct emission from the phase boundary becomes important, the emission
duration signal, i.e., the R_out/R_side ratio, and its sensitivity to T_c (and
thus to the latent heat of the phase transition) are enlarged. Moreover, the
QGP+hadronic rescattering transport model calculations do not yield unusual
large radii (R_i<9fm). Finite momentum resolution effects have a strong impact
on the extracted HBT parameters (R_i and lambda) as well as on the ratio
R_out/R_side.Comment: 4 pages, 2 figure
Directed and Elliptic Flow
We compare microscopic transport model calculations to recent data on the
directed and elliptic flow of various hadrons in 2 - 10 A GeV Au+Au and Pb (158
A GeV) Pb collisions. For the Au+Au excitation function a transition from the
squeeze-out to an in-plane enhanced emission is consistently described with
mean field potentials corresponding to one incompressibility. For the Pb (158 A
GeV) Pb system the elliptic flow prefers in-plane emission both for protons and
pions, the directed flow of protons is opposite to that of the pions, which
exhibit anti-flow. Strong directed transverse flow is present for protons and
Lambdas in Au (6 A GeV) Au collisions as well. Both for the SPS and the AGS
energies the agreement between data and calculations is remarkable.Comment: Latex, 4 pages, 3 eps-figure
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