Limiting fragmentation of chemical potentials in heavy ion collisions

TL;DR

This study extends thermal models to describe rapidity-dependent particle ratios in heavy ion collisions at RHIC energies, revealing a relationship between strange and light quark chemical potentials and supporting limiting fragmentation.

Contribution

It introduces a generalized thermal model approach for rapidity-dependent yields and establishes a specific relationship between strange and light quark chemical potentials.

Findings

Chemical potentials are consistent with limiting fragmentation.

The relation muS = 0.21 +-0.01 muB describes strange and light quark chemical potentials.

Thermal models can describe rapidity dependence of particle ratios at RHIC energies.

Abstract

Thermal models have been used to successfully describe the hadron yields from heavy ion collisions at a variety of energies. For root(S)<17 GeV this has usually been done using yields integrated over 4pi but at the higher energies available at RHIC, yields measured at central rapidity have been used. Recent BRAHMS data allows us to test whether thermal models can be generalized to describe the rapidity dependence of particle ratios. We have used the THERMUS package to fit BRAHMS data for the 5% most central Au+Au collisions for several rapidities at root(S) = 62 and 200 GeV. We have found a relationship between the strange and light quark chemical potentials, muS = 0.21 +-0.01muB. Using this relation we are able to describe the energy dependence of Lambda, Xsi and Omega ratios from other experiments. We also find that the chemical potentials are consistent with limiting fragmentation.