Exploring the QGP phase above the deconfinement temperature in pp and A − A collisions at LHC energies

Abstract

In the present work we have analyzed the transverse momentum spectra of charged particles in high multiplicity pp collisions at LHC energies $\sqrt{s}=5.02$ and 13 TeV published by the ALICE Collaboration using the Color String Percolation Model. For heavy ions Pb-Pb at $\sqrt{s_{NN}}=2.76$ and 5.02 TeV along with Xe-Xe at $\sqrt{s_{NN}}=5.44$ TeV have been analyzed. The initial temperature is extracted both in low and high multiplicity events in pp collisions. For $A-A$ collisions the temperature is obtained as a function of centrality. A universal scaling in the temperature from pp and $A-A$ collisions is obtained when multiplicity is scaled by the transverse interaction area. From the measured energy density ε and the temperature the dimensionless quantity $\epsilon /T^4$ is obtained. Our results for Pb-Pb and Xe-Xe collisions show a sharp increase in $\epsilon /T^4$ above T ∼ 210 MeV and reaching the ideal gas of quarks and gluons value of $\epsilon /T^4\sim 16$ at temperature ∼230 MeV.