Electromagnetic signals from Au plus Au collisions at RHIC energy, √SNN=200 GeV and Pb plus Pb collisions at LHC energy, √SNN=2.76 TeV

We analyse the recently available experimental data on direct photon productions from Au + Au collisions at root S-NN = 200 GeV RHIC and from Pb + Pb collisions at root S-NN = 2.76 TeV LHC energies. The transverse momentum (p(T)) distributions have been evaluated with the assumption of an initial quark gluon plasma phase at energy densities is an element of(i) = 41 and 70 GeV/fm(3) with initial thermalisation times tau(i) = 0.2 and 1.0 fm/c respectively for RHIC and LHC energies. The theoretical evaluations agree well with the experimental observations. The thermal radiations dominate within the p(T) range 1.5 <= p(T)(GeV) <= 3.5. The ratio of thermal photons to dileptons (R-em = [d(2)N(gamma)/d(2)p(T) dy]/(d(2)N(y*)/d(2)p(T) dy]) determines more precisely the window, as mentioned above. (c) 2012 Elsevier B.V. All rights reserved.