Baselines for higher-order cumulants of net-charge distributions from local charge conservation

Abstract

In studies of heavy-ion collisions, fluctuations of conserved quantities are considered as an important signal of the transition between the hadronic and partonic phases of nuclear matter. In this article, it is investigated how the local charge conservation affects higher-order cumulants of net-charge distributions at LHC energies. Simple expressions for the cumulants are derived under the assumption that particle-antiparticle pairs are produced in local processes from sources that are nearly uncorrelated in rapidity. For calculations with these expressions, one needs to know only the second cumulant of net-charge distribution and low-order cumulants of particle number distribution, which are directly measurable experimentally. It is argued that if one wishes to relate susceptibilities with cumulants of net-proton distributions, the developed model provides a better baseline than the conventional Skellam limit or baselines based on Monte Carlo simulations.