Abstract

There are strong indications that ultra-relativistic heavy ion collisions, produced in accelerators, lead to the formation of a new state of matter: the quark gluon plasma (QGP). This deconfined QCD matter is expected to exist just for very short times after the collision. All the information one can get about the plasma is obtained from the particles that reach the detectors. Among them, heavy vector mesons are particularly important. The abundance of cc¯ and bb¯ states produced in a heavy ion collision is a source of information about the plasma. In contrast to the light mesons, that completely dissociate when the plasma is formed, heavy mesons presumably undergo a partial thermal dissociation. The dissociation degree depends on the temperature and also on the presence of magnetic fields and on the density (chemical potential). So, in order to get information about the plasma out of the quarkonium abundance data, one needs to resort to models that provide the dependence of the dissociation degree on these factors. Holographic phenomenological models provide a nice description for charmonium and bottomonium quasi-states in a plasma. In particular, quasi-normal modes associated with quarkonia states have been studied recently for a plasma with magnetic fields. Here we extend this analysis of quasinormal models to the case when charmonium and bottomonium are inside a plasma with finite density. The complex frequencies obtained are then compared with a Breit Wigner approximation for the peaks of the corresponding thermal spectral functions, in order to investigate the quantitative agreement of the different descriptions of quarkonium quasi-states.

Highlights

  • One of the most fascinating challenges currently faced by physicists is to build a detailed picture of the quark gluon plasma (QGP) from the particles that reach the detectors in heavy ion collisions

  • At the very high energy densities produced in these processes, apparently produce the QGP, a state of matter where color is not confined inside bound states

  • An important source of indirect information about the QGP is the abundance of heavy vector mesons

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Summary

INTRODUCTION

One of the most fascinating challenges currently faced by physicists is to build a detailed picture of the quark gluon plasma (QGP) from the particles that reach the detectors in heavy ion collisions. [6, 7] where the spectral functions representing the quasi-states of heavy vector mesons were calculated. [10], quasinormal modes for heavy vector mesons were studied using the holographic model of [8, 9] This analysis was extended, for the case when a magnetic field is present, in ref. We present an extension of the analysis of heavy vector meson quasinormal modes to the case when the medium has a finite density. The comparison is performed by considering a Breit Wigner approximation for the spectral function peaks Such an approximation provides estimates for the real and imaginary parts of the quasinormal frequencies that are in a very nice agreement with the results obtained directly.

HOLOGRAPHIC MODEL FOR HEAVY VECTOR MESONS
QUASINORMAL MODES AT FINITE DENSITY
Results
COMPARISON WITH SPECTRAL FUNCTION RESULTS
CONCLUSIONS
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