Kaon, antikaon and φ(1020) production in Al+Al collisions at 1.9 A Gev

In this paper the production of K+, K- and phi mesons in Al+Al collisions at incident beam energy of 1.9A GeV is studied. The experiment was performed in GSI/Darmstadt using the FOPI spectrometer. The K-/K+ yields ratio was extracted in a substantial part of the phase-space. The yields ratio was found to be in a good agreement with previous experimental results that served as a proof for in-medium modifications of kaons' properties. In order to quantify the contribution of phi mesons decays to the observed K- mesons yield, the phi meson production probability was estimated. The preliminary result differs by almost two orders of magnitude from the earlier estimate available for heavier (Ni+Ni) system at similar beam energy, in which the number of K- mesons that could stem from phi mesons decays was found to be as high as 20%.