891 research outputs found
Applicability of Monte Carlo Glauber models to relativistic heavy ion collision data
The accuracy of Monte Carlo Glauber model descriptions of minimum-bias
multiplicity frequency distributions is evaluated using data from the
Relativistic Heavy Ion Collider (RHIC) within the context of a sensitive,
power-law representation introduced previously by Trainor and Prindle (TP).
Uncertainties in the Glauber model input and in the mid-rapidity multiplicity
frequency distribution data are reviewed and estimated using the TP centrality
methodology. The resulting errors in model-dependent geometrical quantities
used to characterize heavy ion collisions ({\em i.e.} impact parameter, number
of nucleon participants , number of binary interactions ,
and average number of binary collisions per incident participant nucleon )
are presented for minimum-bias Au-Au collisions at = 20, 62,
130 and 200 GeV and Cu-Cu collisions at = 62 and 200 GeV.
Considerable improvement in the accuracy of collision geometry quantities is
obtained compared to previous Monte Carlo Glauber model studies, confirming the
TP conclusions. The present analysis provides a comprehensive list of the
sources of uncertainty and the resulting errors in the above geometrical
collision quantities as functions of centrality. The capability of energy
deposition data from trigger detectors to enable further improvements in the
accuracy of collision geometry quantities is also discussed.Comment: 27 pages, 4 figures, 11 table
Size fluctuations of the initial source and the event-by-event transverse momentum fluctuations in relativistic heavy-ion collisions
We show that the event-by-event fluctuations of the transverse size of the
initial source, which follow directly from the Glauber treatment of the
earliest stage of relativistic heavy-ion collisions, cause, after hydrodynamic
evolution, fluctuations of the transverse flow velocity at hadronic freeze-out.
This in turn leads to event-by-event fluctuations of the average transverse
momentum, p_T. Simulations with GLISSANDO for the Glauber phase, followed by a
realistic hydrodynamic evolution and statistical hadronization carried out with
THERMINATOR, lead to agreement with the RHIC data. In particular, the magnitude
of the effect, its centrality dependence, and the weak dependence on the
incident energy are properly reproduced. Our results show that bulk of the
observed event-by-event p_T fluctuations may be explained by the fluctuations
of the size of the initial source.Comment: 5 pages, 4 figures, version accepted in PR
Transverse Momentum Correlations in Relativistic Nuclear Collisions
From the correlation structure of transverse momentum in relativistic
nuclear collisions we observe for the first time temperature/velocity structure
resulting from low- partons. Our novel analysis technique does not invoke
an {\em a priori} jet hypothesis. autocorrelations derived from the scale
dependence of fluctuations reveal a complex parton dissipation process
in RHIC heavy ion collisions. We also observe structure which may result from
collective bulk-medium recoil in response to parton stopping.Comment: 10 pages, 10 figures, proceedings, MIT workshop on fluctuations and
correlations in relativistic nuclear collision
Comparative Analysis of the Mechanisms of Fast Light Particle Formation in Nucleus-Nucleus Collisions at Low and Intermediate Energies
The dynamics and the mechanisms of preequilibrium-light-particle formation in
nucleus-nucleus collisions at low and intermediate energies are studied on the
basis of a classical four-body model. The angular and energy distributions of
light particles from such processes are calculated. It is found that, at
energies below 50 MeV per nucleon, the hardest section of the energy spectrum
is formed owing to the acceleration of light particles from the target by the
mean field of the projectile nucleus. Good agreement with available
experimental data is obtained.Comment: 23 pages, 10 figures, LaTeX, published in Physics of Atomic Nuclei
v.65, No. 8, 2002, pp. 1459 - 1473 translated from Yadernaya Fizika v. 65,
No. 8, 2002, pp. 1494 - 150
Fusion cross section for the system <SUP>6</SUP>Li+<SUP>28</SUP>Si at E~36 MeV
The fusion cross section for the system 6Li+28Si has been measured at E~36 MeV. Combining this with the data available at lower energies, the nucleus-nucleus real potentials have been determined for a range of interaction distances
The politics of playing along: radio and regulation in democratic Europe
The loss of localism has been a common trend in most radio markets in Europe
and the United States. Deregulation of ownership led to a concentration
phenomenon that has affected local radios in several western democracies.
New forms of regulation have been considered as possible ways to stop the
erosion of localism by applying rules to markets in the defense of diversity,
pluralism, and the local dimension. This article analyses the local radio market
in Portugal, by assessing the changes in the legislation and by examining the
regulatory action that can, according to its remit, act preventively to avoid
market forces to harm these principles.info:eu-repo/semantics/publishedVersio
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