A Method to Constrain Preferential Emission and Spectator Dynamics in Heavy-Ion Collisions

TL;DR

This paper proposes a new correlation measure using the Pearson coefficient to experimentally quantify the effects of preferential emission and spectator breakup on particle production in heavy-ion collisions, validated through simulations.

Contribution

It introduces a novel Pearson correlation observable that links spectator and particle asymmetries, providing a data-driven way to constrain emission and breakup models in heavy-ion collisions.

Findings

Correlation strength sensitive to spectator fluctuations

Observable robust across pseudorapidity

Provides a new constraint for collision models

Abstract

Longitudinal particle production in heavy-ion collisions is influenced both by preferential emission from participating nucleons and by the breakup of spectator matter, yet quantifying these effects experimentally remains challenging. We introduce a Pearson correlation between spectator and charged-particle forward-backward asymmetries as an experimental probe of these phenomena. Using Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV simulated with A Multi-Phase Transport (AMPT) model, we validate that this correlator provides a robust, pseudorapidity-differential measure of the influence of preferential emission on the longitudinal structure of particle production. We further demonstrate that the correlation strength is sensitive to fluctuations in spectator number, which in experiments arise from evaporation and fragmentation of the spectator remnants. The proposed observable therefore offers a data-driven handle for constraining models of preferential emission and spectator breakup, thereby improving our understanding of the mechanisms that shape the final-state longitudinal distributions in heavy-ion collisions.