High strangeness production in antiproton annihilation at rest on few nucleon systems as a possible signature of quark deconfinement or QGP occurrence

The dependence of the K+ and K− production on the number of nucleons involved in the annihilation process is investigated experimentally in the annihilation at rest on hydrogen, deuterium, 3He and 4He gas targets. Annihilations with any number of prongs (charged pions and kaons, protons and deuterons) are analyzed. Events with and without production of neutral mesons and with and without emission of fast neutrons (that is neutrons involved in the annihilation process) are recognized. The results are consistent with our previous ones on a more restricted sample of annihilation reactions and put in evidence that the strangeness production is lower or higher depending on the reaction channel. As a general trend, the strangeness production is higher in events without neutral mesons and still higher in events with the involvement of a higher number of nucleons. Both K+ and K− productions increase with the number of involved nucleons, but K+ much more. The maximum K+ production is observed in the reaction K+2π+2π−3n on 4He (with the involvement of 3–4 nucleons); compared with the production on hydrogen in the reaction K+π+2π−, the production on 4He is higher by a factor of 31.7±5.5. In the light of some theoretical speculations, this enhancement factor is too high to be explainable in terms of hadronic interactions and could be interpreted as a signature of quark deconfinement and of formation of a quark–gluon plasma.