Event-by-Event Particle Ratio Fluctuations at LHC Energies

Abstract

A Monte Carlo study of identified particle ratio fluctuations at LHC energies is carried out in the framework of HIJING model using the fluctuation variable ν dyn . The simulated events for Pb-Pb collisions at s N N = 2.76 and 5.02 TeV and Xe-Xe collisions at s N N = 5.44 TeV are analyzed. From this study, it is observed that the values of π , K , p , K , and π , p follow the similar trends of energy dependence as observed in the most central collision data by NA49, STAR, and ALICE experiments. It is also observed that ν dyn for all the three combinations of particles for semicentral and central collisions, the model predicted values of ν dyn A , B for Pb-Pb collisions at s N N = 2.76 TeV agree fairly well with those observed in the ALICE experiment. For peripheral collisions, however, the model predicted values of ν dyn π , K are somewhat smaller, whereas for p , K and π , p it predicts larger values as compared to the corresponding experimental values. The possible reasons for the observed differences are discussed. The ν dyn values scaled with charged particle density when plotted against N part exhibit a flat behaviour, as expected from the independent particle emission sources. For p , K and π , p combinations, a departure from the flat trend is, however, observed in central collisions in the case of low p T window when the effect of jet quenching or resonances is considered. Furthermore, the study of ν dyn A , B dependence on particle density for various collision systems (including proton-proton collisions) suggests that at LHC energies ν dyn values for a given particle pair are simply a function of charged particle density, irrespective of system size, beam energy, and collision centrality.