The Ratio of the Φ and J/Ψ Meson Yields as a Possible Signature of the Quark-Gluon Plasma Formation

Abstract

It is very probable that in hadronic matter at high enough density and/or temperature a phase transition takes place which leads to the formation of a plasma consisting of deconfined quarks, antiquarks and gluons. We believe that the QGP phase is present in the central region of some neutron stars and it existed in the early Universe. We do hope that it may occur in head-on collisions of high energy heavy ions, too. If the hadronic matter at high energies is transparent then the QGP will contain almost as many antiquarks as quarks, in other words the baryon number density will be low. If the hadronic matter stops during the collision a baryon rich plasma will be formed. According to the analysis of the CERN experiments with 32S ions of 200 GeV/n energy at least the half of the hadronic matter was stopped, consequently one may assume that the QGP produced in heavy ion collision will be baryon rich at least in this energy region. In future experiments to be performed in CERN and in BNL by the help of colliding beams one hopes to reach the critical values of physical parameters of the QGP formation. These estimated critical values are the following: energy density: e ≈ 1–3 GeV/fm3, temperature: T ≈ 150–200 MeV, baryon density: ρ ≈ (5–10) ρ nucl . During the last decade a great number of suggestions has been formulated for the observable signature of the QGP formation. The most extensively studied possibilities are the emission of lepton pairs, the strangness enhancement, the production of strange antibaryons or exotic particles, the enhancement, the J/Ψ suppression,etc. Here we will concentrate on the combination of the last two possibilities.