Energy flow and multiplicity measurement in ultra-relativistic nucleus-nucleus collisions

Experimental results from the HELIOS set-up (High Energy Lepton and Ion Spectrometer, in operation at the CERN Super Proton Synchrotron to study high-energy nucleus-nucleus collisions) are presented and discussed. The transverse energy differential cross section can be parametrized by a geometrical model. The energy density reached in these collisions is much larger than that inside the nucleon and is in the region of the critical value 2·5 GeV/fm³ obtained from lattice QCD calculations for the deconfinement transition. The transverse momentum spectra of photons agree in shape and absolute cross section with the photon spectra expected from hadronic sources.Presented at the IIIrd International Symposium High Energy Experiments And Methods (HEXAM '89), Bechyn, Czechoslovakia, June 25–30, 1989.I would like to thank the organizers of the HEXAM'89 Symposium in Bechyn for giving me the opportunity to participate in this very pleasant and stimulating conference and the hospitality they have extended. This work was supported in part by the National Sciences and Engineering Research Council of Canada (NSERC).