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

We introduce a novel experimental method to quantify contribution of preferential emission to the pseudorapidity distribution of produced particles in heavy-ion collisions using correlations between spectator asymmetry and final-state multiplicity. Within a transport model, the magnitude of this correlator increases from mid to forward rapidities, reflecting the impact of preferential emission and capturing fluctuations in sources of particle production. The correlator demonstrates sensitivity to spectator number fluctuations arising from evaporation or fragmentation, providing a handle to constrain such dynamics. This method serves as a powerful tool to probe particle production mechanisms and the space-time evolution of spectator matter in heavy-ion collisions.