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 ${\it pp}$ collisions at LHC energies $\sqrt s = $ 5.02 and 13 TeV published by the ALICE Collaboration using the Color String Percolation Model (CSPM). 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 ${\it pp}$ 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 $\bm \varepsilon$ and the temperature the dimensionless quantity $\bm \varepsilon/T^{4}$ is obtained. Our results for Pb-Pb and Xe-Xe collisions show a sharp increase in $\bm \varepsilon/T^{4}$ above T $\sim$ 210 MeV and reaching the ideal gas of quarks and gluons value of $\bm \varepsilon/T^{4} \sim$ 16 at temperature $\sim $ 230 MeV. In case of $pp$ collisions only $\bm \varepsilon/T^{4} \sim $ 10 corresponding to $\sim$ 30 degrees of freedom.