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 √sNN = 200 GeV, Pb$-$Pb collisions at √sNN = 2.76 TeV and 5.02 TeV using the Pythia 8 Angantyr model. The centrality dependence of ωch observable, which quantifies the fluctuations in terms of scaled variance is studied for different pseudorapidity ranges and has been compared with those obtained from a simple participant superposition model. The ωch 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.