Methods for Centrality Determination Using Forward Detectors in the BM@N Experiment

Abstract

Collision centrality is a key parameter for studying nuclear matter properties, as it determines the initial interaction geometry and the size of the produced system. Accurate centrality determination is essential for comparing experimental data obtained from different experiments and for benchmarking against theoretical models. This work presents a modification of the approach for centrality determination using charged particle multiplicity based on Bayes' theorem. The proposed improvements enable an estimation of event registration efficiency as a function of the impact parameter. Furthermore, two approaches utilizing forward detectors are proposed: a two-dimensional method based on the combined analysis of track hit counts and spectator deposited energy in the Forward Hadron Calorimeter FHCal, and a method employing signals from the quartz hodoscope and FHCal. These methods were applied to data from the first physics run Xe+CsI of the BM@N experiment (Baryonic Matter at Nuclotron) with a xenon beam at the energy of 3.8 A GeV. A comparison of the developed methods with the classical Monte Carlo Glauber approach demonstrates agreement within 5% across all considered methods, confirming their reliability and mutual consistency. The use of forward detectors for centrality determination may serve as an independent tool for assessing the initial collision geometry and can reduce autocorrelation effects in studies of proton multiplicity fluctuations. The developed approaches can be employed for data processing in the BM@N experiment, as well as in other heavy-ion experiments at intermediate energies.