ON THE PHOTON PRODUCTION IN NUCLEUS-NUCLEUS COLLISIONS AT HIGH-ENERGY

A modified Landau hydrodynamical model is applied to study hard therma l photon production in central heavy-ion collisions at LHC, RHIC and S PS energies. It is shown that the phase transition from quark-gluon pl asma into hadrons in consequence of the thermodynamical expansion is c lose to the second order phase transition if a resonance production is taken into account. Hard direct photon emission is also investigated with consideration of nuclear shadowing effect on structure function o f quarks and gluons. Also pi0-decay photon background is investigated. It is demonstrated that at the LHC energy photon yield from the quark -gluon plasma in the photon transversal momentum k(perpendicular) rang e from 5 to 25 GeV/c exceeds both the background and the direct photon yield. This conclusion may be important for the quark-gluon plasma di agnostic aims. It is also shown that for the LHC energy the thermal ph oton yield in the present model essentially exceeds this yield obtaine d in the Bjorken scaling model.