Impact-parameter dependences of the number of interacting nucleons and mean multiplicities in heavy-ion collisions

The impact-parameter dependence of the mean number of interacting nucleons in high-energy heavy-ion collisions is considered in the case of identical atomic weights of colliding nuclei and in the case where one nucleus is muc h heavier than the other. It is shown that the use of a rare event-for exam ple, an event of J/psi or Y production-as a trigger may change significantl y quantities representing the averages of the multiplicities for accompanyi ng secondaries over impact-parameter values. The multiplicities of accompan ying particles in central collisions can have but a slight dependence on th e trigger. The observed multiplicity ratios for various secondaries in cent ral and minimum-bias events can be used as a test in searches for quark-glu on plasma. (C) 2000 MAIK "Nauka/Interperiodica".