Effects of global charge conservation on time evolution of cumulants of conserved charges in relativistic heavy ion collisions

TL;DR

This paper studies how global charge conservation influences the evolution of fluctuations in conserved charges during relativistic heavy ion collisions, highlighting the importance of diffusion and experimental measurements of cumulants.

Contribution

It demonstrates that global charge conservation effects are negligible for net-electric charge fluctuations observed by ALICE due to finite diffusion, and proposes experimental methods to estimate these effects.

Findings

Global charge conservation has minimal impact on net-electric charge fluctuations in experiments.

Finite diffusion distance explains the negligible effect of global charge conservation.

Combining cumulant measurements across rapidity windows can estimate conservation effects.

Abstract

We investigate the effect of the global charge conservation on the cumulants of conserved charges observed in relativistic heavy ion collisions in a finite rapidity window, $\Delta\eta$, with a special emphasis on the time evolution of fluctuations in the hadronic medium. It is argued that the experimental result of the net-electric charge fluctuation observed by ALICE does not receive effects from the global charge conservation, because of the finite diffusion distance of charged particles in the hadronic stage. We emphasize that the magnitude of the effect of the global charge conservation can be estimated experimentally by combining the information on the $\Delta\eta$ dependences of various cumulants of conserved charges, similarly to other dynamical properties of the hot medium.