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

Abstract

We present a study of transverse momentum ($p_T$) spectra of unidentified charged particles in pp collisions at RHIC and LHC energies from $\sqrt{s}$ = 62.4 GeV to 13 TeV using Tsallis/Hagedorn function. The power law of Tsallis/Hagedorn form gives excellent description of the hadron spectra in $p_T$ range from 0.2 to 300 GeV/$c$. The power index $n$ of the $p_T$ distributions is found to follow a function of the type $a+b/\sqrt{s}$ with asymptotic value $a=5.72$. 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 $p_T$ spectra of hadrons in pPb and different centralities of PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. 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 $p_T$ region and to the in-medium energy loss in high $p_T$ region.