Subthreshold production of K⁺ mesons and the fragmentation of the target nucleus

Abstract

The interplay between subthreshold K⁺-production and the fragmentation of the target nucleus is considered in proton-nucleus interactions at projectile energies between 0.8 and 1 GeV. Inclusive data for the production of K⁺ mesons and of fragments are well described in the framework of the modified phase space model. For a coincidence measurement between K⁺ mesons and fragments the model predicts a decrease of the relative yield of intermediate mass fragments by about four orders of magnitude. This strong decrease is a consequence of energy-momentum conservation, because at subthreshold energies a second endothermic process like multifragmentation can hardly proceed simultaneously with the K⁺ production. A K⁺ meson is, therefore, expected to be accompanied by a heavy target residue, which is so weakly excited that it may evaporate a few nucleons but cannot decay into fragments. Due to the large energy and momentum transfer in this process the strength of the predicted effect is supposed to be sensitive to the details of the reaction dynamics.