BARYON-ANTIBARYON PAIR PRODUCTION IN STRONG MESON FIELDS

According to the relativistic mean-field model, strong meson fields exist in normal nuclei. Even stronger meson fields may be generated in highly compressed and excited hadronic matter formed in relativistic heavy-ion collisions. The attractive interaction of baryons with a scalar field results in a significant reduction of the energy gap in the Dirac spectrum. The interaction with a vector field generated by baryon-rich medium is repulsive for baryons and attractive for antibaryons. At high enough densities, the minimal energy of antibaryons may become lower then -m(B), where m(B) is the baryon mass in vacuum. Such a system becomes unstable with respect to the spontaneous creation of baryon-antibaryon pairs. This phenomenon is estimated to occur at densities exceeding the normal nuclear density by factor 3-7, depending on the coupling constants. Spontaneous as well as induced pair creation will modify drastically both the antiproton and antihyperon production in relativistic heavy-ion collision. This could have a serious impact on recent proposal to use enhanced antihyperon production as an unambiguous signal for the quark-gluon plasma.