Centrality dependence of subthresholdϕmeson production in Ni + Ni collisions at1.9AGeV

We analyzed the ϕ meson production in central Ni + Ni collisions at a beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found a production probability per event of [8.6±1.6(stat)±1.5(syst)]×10−4. This new data point allows us for the first time to inspect the centrality dependence of subthreshold ϕ meson production in heavy-ion collisions. The rise of ϕ meson multiplicity per event with mean number of participants can be parametrized by a power function with exponent α=1.8±0.6. The ratio of ϕ to 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±0.05.Received 13 February 2016DOI:https://doi.org/10.1103/PhysRevC.94.014901©2016 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle & resonance productionRelativistic heavy-ion collisionsNuclear Physics