Study of Pion Transverse Momentum Distributions in Ultra-Relativistic Heavy Ion Collisions: A USTFM Approach

Abstract

The mid-rapidity (|y| < 0.5) transverse momentum distributions of identified charged pions produced in different collision systems at different centre-of-mass energies (${{\sqrt S }_{{NN}}}$) ranging from RHIC to LHC have been studied using our early proposed unified statistical thermal freeze-out model (USTFM). We have also studied the effect of different collision centralities on the mid-rapidity (|y| < 0.5) production of pions. Our model results are found to be in good agreement with the experimental data. Different thermal freeze-out conditions which include transverse flow, thermal freeze-out temperature, and velocity profile have been extracted by providing the best fit to the experimental data points. We have incorporated the effects of transverse as well as longitudinal flow in this analysis. The effects of heavier decay resonances are also taken into account. Moreover, the strangeness conservation criteria have also been imposed in this analysis of pion distributions. The calculated freeze-out parameters indicates that the freeze-out temperature increases with decreasing centrality, while the transverse flow velocity increases by increase in the centrality of the colliding system.