Centrality dependence of subthreshold $\ddot{I}•$ meson production in Ni+Ni collisions at 1.9A GeV

Abstract

We analysed the $\ddot{I}•$ meson production in central Ni+Ni collisions at the beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found the production probability per event of $[8.6\pm 1.6(\text{stat})\pm 1.5(\text{syst})]\times 10^{-4}$. This new data point allows for the first time to inspect the centrality dependence of the subthreshold $\ddot{I}•$ meson production in heavy-ion collisions. The rise of $\ddot{I}•$ meson multiplicity per event with mean number of participants can be parameterized by the power function with exponent $\hat{I}\pm =1.8\pm 0.6$. The ratio of $\ddot{I}•$ to ${\text{K}}^{-}$ production yields seems not to depend within the experimental uncertainties on the collision centrality, and the average of measured values was found to be $0.36\pm 0.05$.

9 pages, 5 figures