Centrality dependence of K+ flow in 58Ni + 58Ni collisions at 1.91A GeV measured with FOPI detector

Kaon production in Ni + Ni heavy-ion collisions at 1.91A GeV was measured by the FOPI collaboration at the heavy-ion synchrotron (SIS) at GSI making use of the newly installed MMRPC barrel [1]. Sub-threshold kaon production is expected to provide valuable insight into the properties of hadrons at high density [2]. The kaon-nucleon potential is expected to enhance the in-medium effective mass for K and to reduce the effective mass for K− if the system becomes more dense. Thus, the production of a K will require more energy while the production of a K− will require less energy in a dense system. Furthermore, the repulsive kaon-nucleon potential tends to make kaons flow away from nucleons and the attractive antikaon-nucleon potential is expected to let anti-kaons flow similar to nucleons. Since the magnitude of these medium effects on charged kaons depends on the strength of the kaon-nucleon potential [2], in principle it is possible to deduce this strength from the measurement of charged kaon flow in heavy-ion collisions.