Characterizing quark gluon plasma by thermal photons and lepton pairs

TL;DR

This paper analyzes thermal photon and lepton pair spectra from heavy-ion collisions at LHC energies to extract properties of the quark-gluon plasma, comparing results across different collider energies and predicting dilepton spectra.

Contribution

It introduces a method to characterize quark-gluon plasma properties using thermal photon and dilepton spectra, with predictions for LHC energies based on initial conditions constrained by photon data.

Findings

Photon spectra reveal the rise in effective degeneracy with multiplicity.

Lepton pair spectra slopes suggest the average radial flow velocity.

Predicted dilepton spectra at LHC energies for future experimental comparison.

Abstract

The photon spectra measured by the ALICE collaboration in Pb+Pb collisions at Large Hadron Collider (LHC) energies has been analyzed with a view of extracting the properties of thermal system formed in these collisions. The results of the analysis are compared with the previously studied spectra measured at Super Proton Synchrotron (SPS) and Relativistic Heavy Ion Collider (RHIC) energies. The thermal dilepton spectra from the Pb+Pb collision at LHC energy has been predicted for the initial conditions constrained by the thermal photon spectra at the same collision conditions. The slope of the photon has been used to estimate the rise in the effective degeneracy with the charged particle multiplicity of the system. The slopes of the lepton pair spectra for different invariant mass windows have been used to conjecture the average radial flow velocity of the high temperature phase.