K+ production in the reaction Ni-58+Ni-58 at incident energies from 1 to 2 A GeV

Semi-inclusive triple differential multiplicity distributions of positively charged kaons have been measured over a wide range in rapidity and transverse mass for central collisions of Ni-58 With Ni-58 nuclei. The transverse mass (m(t)) spectra have been studied as a function of rapidity at a beam energy 1.93 A GeV. The m(t) distributions of K+ mesons are well described by a single Boltzmann-type function. The spectral slopes are similar to that of the protons indicating that rescattering plays a significant role in the propagation of the kaon. Multiplicity densities have been obtained as a function of rapidity by extrapolating the Boltzmann-type fits to the measured distributions over the remaining phase space. The total K+ meson yield has been determined at beam energies of 1.06, 1.45, and 1.93 A GeV, and is presented in comparison to existing data. The low total yield indicates that the K+ meson can not be explained within a hadro-chemical equilibrium scenario, therefore indicating that the yield does remain sensitive to effects related to its production processes such as the equation of state of nuclear matter and/or modifications to the K+ dispersion relation. (C) 1997 Elsevier Science B.V.