8,837 research outputs found
Hydrogen-like Atoms from Ultrarelativistic Nuclear Collisions
The number of hydrogen-like atoms produced when heavy nuclei collide is
estimated for central collisions at the Relativistic Heavy Ion Collider using
the sudden approximation of Baym et al. As first suggested by Schwartz, a
simultaneous measurement of the hydrogen and hadron spectra will allow an
inference of the electron or muon spectra at low momentum where a direct
experimental measurement is not feasible.Comment: 6 pages, 4 figure
From Color Fields to Quark Gluon Plasma
We discuss a model for the energy distribution and the early space-time
evolution of a heavy ion collision. We estimate the gluon field generated in
the wake of hard processes and through primordial fluctuations of the color
charges in the nuclei. Without specifying the dynamical mechanism of
thermalization we calculate the energy momentum tensor of the following plasma
phase. The results of this model can be used as initial conditions for a
further hydrodynamic evolution.Comment: Contribution to Quark Matter 2005; 4 pages, 4 figure
Prompt Photon and Inclusive Production at RHIC and LHC
We present results for prompt photon and inclusive production in p-p
and A-A collisions at RHIC and LHC energies. We include the full
next-to-leading order radiative corrections and nuclear effects, such as
nuclear shadowing and parton energy loss. We find the next-to-leading order
corrections to be large and dependent. We show how measurements of
production at RHIC and LHC, at large , can provide valuable
information about the nature of parton energy loss.
We calculate the ratio of prompt photons to neutral pions and show that at
RHIC energies this ratio increases with approaching one at
GeV, due to the large suppression of production. We show that at the
LHC, this ratio has steep dependence and approaches 10% effect at GeV.Comment: Talk presented by I. Sarcevic, to appear in the Proceedings of Quark
Matter 2002; 4 pages including 4 color figure
Zero range model of traffic flow
A multi--cluster model of traffic flow is studied, in which the motion of
cars is described by a stochastic master equation. Assuming that the escape
rate from a cluster depends only on the cluster size, the dynamics of the model
is directly mapped to the mathematically well-studied zero-range process.
Knowledge of the asymptotic behaviour of the transition rates for large
clusters allows us to apply an established criterion for phase separation in
one-dimensional driven systems. The distribution over cluster sizes in our
zero-range model is given by a one--step master equation in one dimension. It
provides an approximate mean--field dynamics, which, however, leads to the
exact stationary state. Based on this equation, we have calculated the critical
density at which phase separation takes place. We have shown that within a
certain range of densities above the critical value a metastable homogeneous
state exists before coarsening sets in. Within this approach we have estimated
the critical cluster size and the mean nucleation time for a condensate in a
large system. The metastablity in the zero-range process is reflected in a
metastable branch of the fundamental flux--density diagram of traffic flow. Our
work thus provides a possible analytical description of traffic jam formation
as well as important insight into condensation in the zero-range process.Comment: 10 pages, 13 figures, small changes are made according to finally
accepted version for publication in Phys. Rev.
Particle yield fluctuations and chemical non-equilibrium at RHIC
We study charge fluctuations within the statistical hadronization model.
Considering both the particle yield ratios and the charge fluctuations we show
that it is possible to differentiate between chemical equilibrium and
non-equilibrium freeze-out conditions. As an example of the procedure we show
quantitatively how the relative yield ratio together with the
normalized net charge fluctuation v(Q)=\ave{\Delta Q^2}/\ave{\Nch} constrain
the chemical conditions at freeze-out. We also discuss the influence of the
limited detector acceptance on fluctuation measurements, and show how this can
be accounted for within a quantitative analysis.Comment: Accepted for publication by Physical Review
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