Examination of the species and beam energy dependence of particle spectra using Tsallis statistics

Abstract

Tsallis Statistics was used to investigate the non-Boltzmann distribution of\nparticle spectra and their dependence on particle species and beam energy in\nthe relativistic heavy-ion collisions at SPS and RHIC. Produced particles are\nassumed to acquire radial flow and be of non-extensive statistics at\nfreeze-out. J/psi and the particles containing strangeness were examined\nseparately to study their radial flow and freeze-out. We found that the strange\nhadrons approach equilibrium quickly from peripheral to central A+A collisions\nand they tend to decouple earlier from the system than the light hadrons but\nwith the same final radial flow. These results provide an alternative picture\nof freeze-outs: a thermalized system is produced at partonic phase; the\nhadronic scattering at later stage is not enough to maintain the system in\nequilibrium and does not increase the radial flow of the copiously produced\nlight hadrons. The J/psi in Pb+Pb collisions at SPS is consistent with early\ndecoupling and obtains little radial flow. The J/psi spectra at RHIC are also\ninconsistent with the bulk flow profile.\n