Evolution of Effective Temperature, Kinetic Freeze-out Temperature and transverse flow velocity in pp Collision

TL;DR

This study analyzes strange hadron production in proton-proton collisions at various energies using statistical models, revealing energy-dependent freeze-out parameters and mass-related freeze-out scenarios.

Contribution

It introduces a detailed analysis of freeze-out parameters across multiple energies and particle masses, highlighting the mass differential and multi-freeze-out scenarios in pp collisions.

Findings

Effective temperature and freeze-out temperature increase with collision energy.

Mass-dependent freeze-out parameters support multi-freeze-out scenario.

Inverse relationship between non-extensivity parameter q and particle mass.

Abstract

This article focuses on the study of strange hadrons at 0.2 TeV centre of mass energy, recorded by STAR at RHIC, and at 0.9 TeV, 5.02 TeV and 7 TeV, recorded by CMS at LHC, in pp collision in the rapidity range from 0 to 2. The transverse momentum distributions of these strange particles have been processed using two statistical models, the Tsallis and the modified Hagedorn model. Both models fit the experimental data well. We extracted different freezeout parameters from the fit procedure using the abovementioned functions. We found that with increasing the collision energy, the effective temperature (T), in the case of the Tsallis model, and kinetic/thermal freeze-out temperature (T0) and transverse flow velocity, in the case of the modified Hagedorn model, increase because of greater energy transfer among the participants at higher colliding energies. Both T and T0 are observed to increase with the increase in the rest masses of the outgoing particles revealing the multi-freeze-out scenario. Furthermore, the multiplicity parameter (N0) decreases with the increase in the particle mass, confirming the mass differential freeze-out scenario. An inverse relationship between the non-extensivity parameter (q) and the masses of the produced particles has been noticed. Similarly, an inverse correlation between q and T has been found. For lighter particles, smaller T and greater q mean that they decouple from the system later and attain equilibrium slowly compared to heavier ones. In addition, a positive correlation between transverse flow velocity and T0 is noticed, which agrees with the literature.