ABSTRACT
The forthcoming experiment of the NA34 collaboration consists, indeed, of two parts, one devoted to pN collisions, the other to AA collisions; the case of pA is, to some extent, incorporated in both. In the few years, various signals have been suggested as probes of the transient plasma of locally unconfined quarks and gluons expected to occur in high energy nucleus-nucleus collisions. Among these, direct photons and lepton pairs are particularly attractive: the Stefan-Boltzmann behaviour of the thermal production rates favors the hottest stages of the collision, and theabsence of final state interactions allows to directly view the interior. The spectra of real photons are investigated with several different approaches. Smaller components exist, in addition, for the detection of real photons. A sixth major component, an electron spectrometer at larger angles, may be added in the future for the nuclear case.
