Hard π0 and η production in S+ Au nuclear collisions at SPS energies and possible signature of quark-gluon plasma

Abstract

Hard π 0 and η production is investigated in Landau and Bjorken hydrodynamical models taking into account great number of hadronic resonances (16 and 42) in hadronic phase. We consider two different scenario: with quark-gluon plasma (QGP) formation and with only hadronic gas one without QGP. The Cronin effect and hard direct pions emission are taken into account. It is shown that these two scenario give similar p ⊥ spectra which agrees with experimental data obtained by WA80 collaboration. Therefore we conclude that from hadronic spectra it is difficult to extract the proof of QGP formation. However we calculate also the η/ π 0 ratio. We show that this value agrees with experiment only for scenario with QGP and phase transition to hadrons. The hadronic gas scenario without QGP disagrees with experimental data.