Influence of Backside Energy Leakages from Hadronic Calorimeters on Fluctuation Measures in Relativistic Heavy-Ion Collisions

Abstract

The phase diagram of the strongly interacting matter is the main research subject for different current and future experiments in high-energy physics. System size and energy scan programs aim to find a possible critical point. One of such programs was accomplished by the fixed-target NA61/SHINE experiment in 2018. It includes six beam energies and six colliding systems: p + p, Be + Be, Ar + Sc, Xe + La, Pb + Pb and p + Pb. In this study, we discuss how the efficiency of centrality selection by forward spectators influences multiplicity and fluctuation measures and how this influence depends on the size of colliding systems. We use SHIELD and EPOS Monte-Carlo (MC) generators along with the wounded nucleon model, introduce a probability to lose a forward spectator and spectator energy loss. We show that for light colliding systems such as Be or Li even a small inefficiency in centrality selection has a dramatic impact on multiplicity scaled variance. Conversely, heavy systems such as Ar + Sc are much less prone to the effect.Universe 2019, 5, 126 2 of 8 Study with a Geant Calorimeter ModelThe main motivation for this work was a study of how Projectile Spectator Detector (PSD) [9] influences the measured quantities in the NA61/SHINE collaboration [10]. PSD is a segmented modular hadronic calorimeter, which is used for triggering, centrality and event plane determination. The detector consists of 44 independent modules and each of them has 60 lead (16 mm) + scintillator (4 mm) layers. The total length of PSD is about 1.2 m, which corresponds to approximately 5.6 interaction lengths. A scheme of the NA61/SHINE setup and a photo of PSD are presented in Figure 1.