Trace initial interaction from final state observable in relativistic heavy ion collisions

TL;DR

This paper proposes azimuthal multiplicity-correlation patterns to trace initial interactions in relativistic heavy ion collisions, revealing model-independent regularities in correlation pattern evolution with collision centrality.

Contribution

It introduces new correlation patterns to analyze initial interactions and demonstrates their model-independent behavior across different energies and models.

Findings

Correlation patterns shift from out-of-plane to in-plane with increasing centrality.

Anisotropic flow v_2 remains positive across all centralities.

Correlation patterns are independent of collision energy and model used.

Abstract

In order to trace the initial interaction in ultra-relativistic heavy ion collision in all azimuthal directions, two azimuthal multiplicity-correlation patterns -- neighboring and fixed-to-arbitrary angular-bin correlation patterns -- are suggested. From the simulation of Au + Au collisions at 200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting, we observe that the correlation patterns change gradually from out-of-plane preferential one to in-plane preferential one when the centrality of collision shifts from central to peripheral, meanwhile the anisotropic collective flow v_2 keeps positive in all cases. This regularity is found to be model and collision energy independent. The physics behind the two opposite trends of correlation patterns, in particular, the presence of out-of-plane correlation patterns at RHIC energy, are discussed.