Influence of phi mesons on negative kaons in Ni plus Ni collisions at 1.91A GeV beam energy

Abstract

phi and K- mesons from Ni + Ni collisions at the beam energy of 1.91A GeV have been measured by the FOPI spectrometer, with a trigger selecting central and semicentral events amounting to 52% of the total cross section. The phase-space distributions, and the total yield of K-, as well as the kinetic energy distribution and the total yield of f mesons are presented. The phi/K- ratio is found to be 0.44 +/- 0.07 (stat)(-0.10)(+0.16)(syst), meaning that about 22% of K- mesons originate from the decays of f mesons, occurring mostly in vacuum. The inverse slopes of direct kaons are up to about 15 MeV larger than the ones extracted within the one-source model, signaling that a considerable share of gap between the slopes of K+ and K- could be explained by the contribution of f mesons to negative kaons.