Indication of transverse radial flow in high-multiplicity proton–proton collisions at the Large Hadron Collider

Abstract

We analyze the measured spectra of π±, K±, p() in proton–proton (pp) collisions at = 0.9, 2.76 and 7 TeV in the light of blast-wave model to extract the transverse radial flow velocity and kinetic temperature at freeze-out for the system formed in pp collisions. The dependence of the blast-wave parameters on average charged particle multiplicity of event sample or the ‘centrality’ of collisions has been studied and compared with results of similar analysis in nucleus–nucleus (AA) and proton–nucleus (pA) collisions. We analyze the spectra of , Λ() and Ξ− also to see the dependence of blast-wave description on the species of produced particles. Within the framework of the blast-wave model, the study reveals indication of collective behavior for high-multiplicity events in pp collisions at LHC. Strong transverse radial flow in high-multiplicity pp collisions and its comparison with that in pA and AA collisions match with predictions from a very recent theoretical work (Shuryak and Zahed 2013 arXiv:hep-ph/1301.4470) that addresses the conditions for applicability of hydrodynamics in pp and pA collisions.