A Two-dimensional Bayesian Approach to Centrality Determination in Nucleus-Nucleus Collisions

The determination of centrality in nucleus-nucleus collisions is a crucial task, as it enables the estimation of the impact parameter and thereby allows for the comparison of experimental results with predictions from theoretical models and other experiments. In this work, we present a two-dimensional approach for centrality determination based on a Bayesian framework. The observables used were the number of track hits and the deposited energy of spectators in the forward hadronic calorimeter. A distribution is proposed to describe the fluctuations of these two observables at a fixed impact parameter value. This distribution provides a more precise description of the observable distributions in both central and peripheral regions. The effectiveness of the proposed method was tested within a realistic BM@N simulation framework for Xe+CsI collisions at a beam energy of 3.8A GeV.