Collectivity in small systems - Initial state vs. final state effects

TL;DR

This paper investigates the origins of long-range azimuthal correlations in small collision systems, emphasizing the importance of a unified theoretical approach to distinguish initial state effects from final state responses.

Contribution

It presents initial results from weakly coupled non-equilibrium simulations to quantify the roles of initial and final state effects in small system collisions.

Findings

Initial state momentum correlations contribute significantly to observed effects.

Final state response also plays a crucial role in azimuthal correlations.

Simulations help disentangle initial and final state contributions.

Abstract

Observations of long rang azimuthal correlations in small collision systems (p+p/A) have triggered an enormous excitement in the heavy-ion community. However, it is presently unclear to what extent the experimentally observed correlations should be attributed to initial state momentum correlations and/or the final state response to the initial state geometry. We discuss how a consistent theoretical description of the non-equilibrium dynamics is important to address both effects within a unified framework and present first results from weakly coupled non-equilibrium simulations in \cite{Greif:2017bnr} to quantify the relative importance of initial state and final state effects based on theoretical calculations.