Event plane dependence of the flow modulated background in di-hadron and jet-hadron correlations in heavy ion collisions

TL;DR

This paper derives the shape of flow-modulated backgrounds in di-hadron and jet-hadron correlations for arbitrary event plane orders, accounting for phase shifts and correlations between event planes, to improve understanding of jet quenching in heavy ion collisions.

Contribution

It extends the theoretical description of flow backgrounds to arbitrary event plane orders, including phase shifts and event plane correlations, enhancing analysis accuracy in heavy ion collision studies.

Findings

Derived background shape for arbitrary event plane order.

Identified phase shift effects for asymmetric jet regions.

Assessed impact of event plane correlations on background shape.

Abstract

Di-hadron and jet-hadron correlations are commonly used in relativistic heavy ion collisions to study the soft component of jets in a quark gluon plasma. There is a large correlated background which is described by the Fourier decomposition of the azimuthal anisotropy where $v_n$ is the $n$th order coefficient. The path length dependence of partonic energy loss can be studied by varying the angle of the high momentum trigger particle or jet relative to a reconstructed event plane. This modifies the shape of the background correlated with that event plane. The original derivation of the shape of this background only considered correlations relative to the second order event plane, which is correlated to the initial participant plane. We derive the shape of this background for an event plane at an arbitrary order. There is a phase shift in the case of jets restricted to asymmetric regions relative to the event plane. For realistic correlations between event planes, the correlation between the second and fourth order event planes leads to a much smaller effect than the finite event plane resolution at each order. Finally, we assess the status of the rapidity even $v_1$ term due to flow, which has been measured to be comparable to $v_2$ and $v_3$ terms.