925 research outputs found
Non-simple localizations of finite simple groups
Often a localization functor (in the category of groups) sends a finite
simple group to another finite simple group. We study when such a localization
also induces a localization between the automorphism groups and between the
universal central extensions. As a consequence we exhibit many examples of
localizations of finite simple groups which are not simple.Comment: 10 page
Jets propagation through a hadron-string medium
Di-jet correlations in nucleus-nucleus collisions are studied within the
Hadron-String-Dynamics (HSD) transport approach taking into account the
reaction of the medium on the jet energy loss nonperturbatively. A comparison
with the STAR and PHENIX data in central Au+Au collisions at the RHIC energy
GeV is performed differentially, i.e. with respect to
correlations in azimuthal angle and pseudorapidity .
The HSD results do not show enough suppression for the `away-side' jets in
accordance with earlier perturbative studies. Furthermore, the `Mach-cone'
structure for the angle distribution in the `away-side' jet as well as `ridge'
long rapidity correlations in the `near-side' jet - observed by the STAR and
PHOBOS Collaborations - are not seen in the HSD results, thus suggesting a
partonic origin.Comment: 7 pages, 3 figure
Fluctuations and Correlations in Nucleus-Nucleus Collisions within Transport Models
Particle number fluctuations and correlations in nucleus-nucleus collisions
at SPS and RHIC energies are studied within microscopic transport approaches.
In this review we focus on the Hadron-String-Dynamics (HSD) and
Ultra-relativistic-Quantum-Molecular-Dynamics (UrQMD) models The obtained
results are compared with the available experimental data as well as with the
statistical models and the model of independent sources. In particular the role
of the experimental centrality selection and acceptance is discussed in detail
for a variety of experimental fluctuations and correlation observables with the
aim to extract information on the critical point in the plane of
strongly interacting matter
Fluctuations and correlations from microscopic transport theory
The multiplicity fluctuations in A+A collisions at SPS and RHIC energies are studied within the HSD transport approach. We find a dominant role of the fluctuations in the nucleon participant number for the final fluctuations. In order to extract physical fluctuations one should decrease the fluctuations in the participants number. This can be done considering very central collisions. The system size dependence of the multiplicity fluctuations in central A+A collisions at the SPS energy range – obtained in the HSD and UrQMD transport models – is presented. The results can be used as a ‘background’ for experimental measurements of fluctuations as a signal of the critical point. Event-by-event fluctuations of the K/p , K/p and p/p ratios in A+A collisions are also studied. Event-by-event fluctuations of the kaon to pion number ratio in nucleus-nucleus collisions are studied for SPS and RHIC energies. We find that the HSD model can qualitatively reproduce the measured excitation function for the K/p ratio fluctuations in central Au+Au (or Pb+Pb) collisions from low SPS up to top RHIC energies. The forward-backward correlation coefficient measured by the STAR Collaboration in Au+Au collisions at RHIC is also studied. We discuss the effects of initial collision geometry and centrality bin definition on correlations in nucleus-nucleus collisions. We argue that a study of the dependence of correlations on the centrality bin definition as well as the bin size may distinguish between these ‘trivial’ correlations and correlations arising from ‘new physics’. 5th International Workshop on Critical Point and Onset of Deconfinement - CPOD 2009, June 08 - 12 2009 Brookhaven National Laboratory, Long Island, New York, US
Open and Hidden Charm Production in Heavy Ion Collisions at Ultrarelativistic Energies
We consider the production of the open charm and J/psi mesons in heavy ion
collisions at BNL RHIC. We discuss several recently developed pictures for
J/psi production and argue that a measurement at RHIC energies is crucial for
disentangling these different descriptions.Comment: 19 pages, Latex, 5 PS-figures. v3: Fig.6 is adde
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