Charged particle multiplicity fluctuation in \(A-A\) collisions at RHIC and LHC energies using Angantyr model

Event-by-event fluctuations of the charged particle multiplicity are studied for a wide range of centralities for Au−Au collisions at \(\sqrt{s_{NN}} = 200\hbox { GeV}\), Pb−Pb collisions at \(\sqrt{s_{NN}} = 2.76\hbox { TeV}\) and 5.02 TeV using the Pythia8 Angantyr model. The centrality dependence of \(\omega _{ch}\) observable, which quantifies the fluctuations in terms of scaled variance, is studied for different pseudo-rapidity ranges and has been compared with those obtained from a simple participant superposition model. The \(\omega _{ch}\) was found to be lower than the expectations from the participant model. The estimate would act like a baseline for current and future measurements of event-by-event fluctuations in the charged particle multiplicities in systems at LHC energies where no de-confined medium of quarks and gluons are formed.