  We analyse the recently available experimental data on direct photon
productions from Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV RHIC and from
Pb+Pb collisions at $\sqrt{s_{NN}}$=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 temperatures $T_i$=404 and 546 MeV with
initial thermalisation times $\tau_i$=0.2 and 0.1 fm/c respectively for RHIC
and LHC energies. The theoretical evalutions agree reasonably well with the
experimental observations. The thermal window for the LHC energy is justified
through the ratio of the $p_T$ spectra of thermal photons to dileptons.
