Transverse momentum spectra of hadrons in high energy pp and heavy ion collisions

Kapil Saraswat,Prashant Shukla,Venktesh Singh

doi:10.1088/2399-6528/aab00f

Abstract

We present a study of transverse momentum (pT) spectra of unidentified charged particles in pp collisions at RHIC and LHC energies from to 13 TeV using Tsallis/Hagedorn function. The power law of Tsallis/Hagedorn form gives very good description of the hadron spectra in pT range from 0.2 to 300 GeV/c. The power index n of the pT distributions is found to follow a function of the type with asymptotic value a = 6.8. The parameter T governing the soft bulk contribution to the spectra remains almost same over wide range of collision energies. We also provide a Tsallis/Hagedorn fit to the pT spectra of hadrons in pPb and different centralities of PbPb collisions at . The data/fit shows deviations from the Tsallis distribution which become more pronounced as the system size increases. We suggest simple modifications in the Tsallis/Hagedorn power law function and show that the above deviations can be attributed to the transverse flow in low pT region and to the in-medium energy loss in high pT region.

Highlights

The light hadrons are the most abundant particles produced in the pp and heavy ion collisions
The Tsallis distribution function gives good description of the data for both the collision energies which can be inferred from the values of χ2/NDF given in the Table 1
The Tsallis distribution function gives good description of the data for collision energies which can be inferred from the values of χ2/NDF given in the Table 1

Summary

Introduction

The light hadrons are the most abundant particles produced in the pp and heavy ion collisions. The hadron pT spectra in pp collisions are successfully described by Tsallis distribution [5, 6] in terms of only two parameters, the Tsallis parameter T and the parameter q which governs the degree of non-thermalization. It is well known [7, 8, 9] that the functional form of the Tsallis distribution which describes near-thermal systems is essentially the same as the power law function by Hagedorn which is applicable to QCD hard scatterings [10, 11]. The CMS papers [19, 20]

Objectives

Results

Conclusion