Is the centrality dependence of the elliptic flow v2 and of the average u0001 pT u0002 more than a core-corona effect?

摘要

Recently we showed that the centrality dependence of the multiplicity of different hadron species observed innRelativistic Heavy Ion Collider (RHIC) and Super Proton Synchrotron (SPS) experiments can be well understoodnin a simple model, dubbed the core-corona model. There it is assumed that those incoming nucleons that scatternonly once produce hadrons as in pp collisions whereas those that scatter more often form an equilibrated sourcenwhich decays according to phase space. In this article we showthat also kinematical variables such as v2/u0001part(Npart)nas well as vi2n/u0001part(Npart) and u0001pinT (Npart)u0002 of identified particles are well described in this model. The correlation ofnu0001pinTnu0002 between peripheral heavy-ion collisions and pp collisions for different hadrons, reproduced in this model,nquestions whether hydrodynamical calculations are the proper tool to describe a noncentral heavy-ion collision.nThe model explains as well the centrality dependence of v2/u0001part of charged particles, considered up to now asnan observable that allows us to determine the viscosity of the quark-gluon plasma. The observed dependence ofnvi2n/u0001part(Npart) on the particle species is a simple consequence of the different ratios of core-to-corona particles.