Volume fluctuation and auto-correlation effects in the moment analysis of net-proton multiplicity distributions in heavy-ion collisions

Abstract

Moments (variance (σ2), skewness (S), kurtosis (κ)) of multiplicity distributions of conserved quantities, such as net-baryon, net-charge and net-strangeness, are predicted to be sensitive to the correlation length of the system and connected to the thermodynamic susceptibilities computed in the Lattice QCD and Hadron Resonance Gas model. In this paper, we present several measurement artifacts that could lead to volume fluctuation and auto-correlation effects in the moment analysis of net-proton multiplicity distributions in heavy-ion collisions using the ultra-relativistic quantum molecular dynamics model. We discuss methods to overcome these artifacts so that the extracted moments can be used to obtain physical conclusions. In addition, we present methods to properly estimate the statistical errors in moment analysis.