Determination of centrality in nucleus-nucleus collisions on the MPD/NICA installation.

Measurement of the number of spectators in nucleus-nucleus collisions could be used to determine the number of nucleons participating in the interaction, i.e. get information about collision centrality. However, at energies of the NICA collider energy resolution of the forward hadron calorimeter is insufficient for separation of the amplitudes corresponding to different number of spectators. Uncertainty in the number of spectators leads to a large error in determining the centrality. For central events inaccuracy in determining the collision parameter is about 40%, for peripheral ones, no better than 30% at a beam energy of 2.5 AxGeV. The multiplicity scintillator detector will allow to obtain more accurate data. A certain method is proposed for determining the centrality, taking into account the real MPD installation geometry.