Geometric scaling in symmetric nucleus-nucleus collisions

Abstract

We show that the centrality dependence of the multiplicity is identical in Pb+Pb and Xe+Xe collisions at the LHC, up to a constant factor. This geometric scaling is revealed if one defines centrality according to impact parameter, as opposed to the usual experimental definition, which is in terms of multiplicity. We reconstruct the impact parameter dependence of the multiplicity from experimental data using a recently-developed inversion method, which turns out to describe ALICE Xe+Xe multiplicity data much better than usual Monte Carlo Glauber fits. The multiplicity as function of impact parameter extracted from ALICE data is compared to model calculations.