A unified study of the production of all identified hadrons over wide ranges of transverse momenta at LHC

摘要

The production of all identified hadrons in the heavy-ion collisions at the CERN Large Hadron Collider (LHC) is studied with emphasis on the p(T) distributions up to 20 GeV/c in central Pb+Pb collisions at root s(NN) = 2.76 TeV. The parton recombination model is used to determine the hadronic p(T) spectra from the quark distributions. From the heavy hyperon spectra it is known from earlier studies that the u, d, s thermal distributions in p(T) are exponential with large inverse slopes that cannot be identified with any temperature in conventional fluid models. They are used as inputs in our model together with shower partons determined from our treatment of momentum degradation that uses high-p(T) pion data as input. Those thermal and shower partons are used to calculate the p(T) distributions of all observed hadrons (pi, K, p, Lambda, Xi, Omega and phi) over wide ranges of p(T), so the system is highly constrained. We show how well the LHC data can be reproduced with only a few parameters to adjust. Centrality dependence has not been studied. What is learned is that minijets are important, not only in giving rise to abundant shower partons, but also in the conversion of semihard partons in the medium to soft partons that enhance the thermal partons. Since the conversion process can occur throughout the expansion phase of the high-density medium, the results of this work may be taken to imply that advocacy for the assumption of rapid equilibration needs to be reconciled with the phenomenological evidence that we have found for prolonged creation of soft partons.