System size dependence of hadron pT spectra in p + p and Au+Au collisions at = 200 GeV

Abstract

We make a systematic study of transverse momentum (pT) spectra of hadrons produced in p + p and in different centralities of Au+Au collisions at center of mass energy of 200 GeV using phenomenological fit functions. The Tsallis distribution gives a very good description of hadron spectra in p + p collisions with just two parameters but does not produce the same in Au+Au collisions at intermediate pT. To explain the hadron spectra in heavy ion collisions in a wider pT range we propose a modified Tsallis function by introducing an additional parameter that accounts for collective flow. The new analytical function gives a very good description of both mesons and baryons spectra at all centralities of Au+Au collisions in terms of the parameters having a potential physics interpretation. With this modified Tsallis function we study the spectra of pions, kaons, protons, Λ and Ξ− as a function of system size at = 200 GeV. The parameter representing transverse flow increases with system size and is found to be more for baryons than that for mesons in central Au+Au collisions. The freeze-out temperature for baryons increases with centrality in Au+Au collisions more rapidly than for mesons.