Resolving the antibaryon-production puzzle in high-energy heavy-ion collisions

We argue that the observed antiproton production in heavy-ion collisions at CERN-SPS energies can be understood if (contrary to most sequential scatte ring approaches) the backward direction in the process p (p) over bar <---- > (n) over bar pi (with (n) over bar = 5-6) is consistently accounted for w ithin a thermal framework. Employing the standard picture of subsequent che mical and thermal freezeout, which induces an oversaturation of pion number with associated chemical potentials of mu (pi), similar or equal to 60-80 MeV, enhances the backward reaction substantially. The resulting rates turn out to be large enough to maintain an antiproton abundance at thermal free zeout in accordance with the measured (p) over bar /p ratio in Pb(158A GeV) + Pb collisions.