Subthreshold K--meson production in proton-nucleus reactions revisited

The inclusive K- -meson production in proton-nucleus collisions in the subthreshold energy regime is studied in the framework of an appropriate spectral function approach for incoherent primary proton-nucleon and secondary pion-nucleon production processes, which takes properly into account the nuclear mean-field potential effects on these processes as well as the final state interaction (FSI) among the outgoing nucleons participating in the one-step antikaon creation process. A detailed comparison of the model calculations of the K(-)differential cross sections is given for the reactions p + Be-9, p + Cu-63, and p + Au-197 at subthreshold energies with the currently available experimental data, obtained recently at the ITEP proton synchrotron and at SIS/GSI. It is found that the calculations with inclusion of the influence of both the nuclear density-dependent mean-field potentials and the elementary NN-FSI effects on the K- production from direct mechanism are able to reproduce, contrary to previous estimates based on the use only of the density- dependent mean fields in calculating the K- yield from this mechanism, the energy dependences of the invariant differential cross sections for "hard" antikaon creation in p(9)Be and p(63)Cu collisions. It is further shown that the NN-FSI effects play a minor role in describing the data on the spectrum of relatively soft K- mesons from p(197)Au interactions at incident energy of 2.5 GeV. It is also shown that the relative strength of the proton- and pion-induced reaction channels in the subthreshold energy regime is governed by the kinematics of the experiment under consideration. The influence of the nucleon, kaon, and antikaon mean-field potentials on the K- yield is explored. It is demonstrated that, in line with previous findings, the K- optical potential has a strong effect on this yield at low antikaon momenta, which is greater than those from nucleon and kaon effective potentials. At high antikaon momenta, the K- yield is found-to be mainly determined, along with the elementary NN-FSI effects, by the nucleon mean field and the scenario with zero K+ potential is favorable. (C) 2002 MAIK "Nauka/lnterperiodica".