Direct photon detection in PbPb collisions in the ALICE experiment at LHC

Direct photons are considered as one of the most important signatures of thermalized quark-gluon matter produced in relativistic heavy-ion collisions. The ALICE experiment at LHC, which is being prepared to study heavy-ion collisions at the energies 5.5A TeV, will be equipped by the photon spectrometer PHOS to detect direct photons and measure their spectrum in a wide momentum range 0 < pT < 100 GeV/c with high precision. Expected yields of direct photons at the LHC energies, as well as experimental methods to measure photon spectrum in the PHOS detector, are discussed in the paper