Electromagnetic signals from Au+Au collisions at RHIC energy, $\sqrt{s_{NN}}$=200 GeV and Pb+Pb collisions at LHC energy, $\sqrt{s_{NN}}$=2.76 TeV

摘要

We analyse the recently available experimental data on direct photonproductions from Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV RHIC and fromPb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV LHC energies. The transversemomentum ($p_T$) distributions have been evaluated with the assumption of aninitial quark gluon plasma phase at temperatures $T_i$=404 and 546 MeV withinitial thermalisation times $\tau_i$=0.2 and 0.1 fm/c respectively for RHICand LHC energies. The theoretical evalutions agree reasonably well with theexperimental observations. The thermal window for the LHC energy is justifiedthrough the ratio of the $p_T$ spectra of thermal photons to dileptons.