On the Possibility of Event Shape Selection in Relativistic Heavy Ion Collisions

TL;DR

This paper explores the feasibility of selecting heavy ion collision events based on initial geometric features by analyzing correlations with final state flow, revealing significant fluctuations that challenge event engineering.

Contribution

It investigates the correlation between initial state geometry and final flow observables, highlighting the impact of fluctuations and rescattering on event selection.

Findings

Large event-by-event fluctuations due to finite particle number and rescattering.

Event engineering by final state selection is challenging.

Correlations between initial geometry and final flow are affected by fluctuations.

Abstract

We investigate the possibility of selecting heavy ion collision events with certain features in the initial state ("event engineering"). Anisotropic flow measurements in heavy ion reactions have confirmed the almost ideal fluid dynamical behaviour of the hot and dense quark gluon plasma state. As a consequence, it is intriguing to pursue the idea of selecting collisions with a certain special initial geometry, e.g., a large ellipsoidal or triangular deformation, by classifying events by the value of their final observed flow coefficients. This procedure could be especially interesting for azimuthally dependent jet energy loss studies. We investigate the correlation between initial state features and final state momentum space anisotropies within an event-by-event hybrid approach. We find that the finite particle number and hadronic rescattering of the final state leads to large event-by-event fluctuations in the observables that could be used to characterize the features of the initial state. This makes event engineering by final state selection difficult.