Direct production of photons and dileptons in thermodynamical models of multiple hadron production

The thermodynamical picture of a hot lump of hadronic matter ('clusters', high-density gluonic clouds and especially suitable cases of hydrodynamical theories of Heisenberg and Landau) naturally leads to direct production of gamma quanta ('black-body radiation') and-in the next order in e/sup 2/-of lepton pairs. At large p/sub T/ their spectra reproduce the main features of the pionic spectrum. The intensity of gamma 's exceeds e/sup 2/ times that of the pi 's, due to the relatively large volume of the radiating system and to the long duration of its expansions. However, since the dynamics of the heated hadronic vacuum is not known, pre-exponential factors cannot be safely calculated. (50 refs).