A remark on the sign change of the four-particle azimuthal cumulant in small systems

TL;DR

This paper investigates how global transverse momentum conservation affects azimuthal cumulants in small systems, revealing a sign change in $c_2 ext{ }\{4\}$ that aligns with recent experimental observations.

Contribution

It provides a theoretical calculation showing the sign change of $c_2\{4\}$ due to momentum conservation in small systems, connecting it with experimental data.

Findings

Sign change of $c_2\{4\}$ in small particle systems.

Qualitative agreement with ATLAS measurements.

Highlights the role of momentum conservation in azimuthal correlations.

Abstract

The azimuthal cumulants, $c_2\{2\}$ and $c_2\{4\}$, originating from the global conservation of transverse momentum in the presence of hydro-like elliptic flow are calculated. We observe the sign change of $c_2\{4\}$ for small number of produced particles. This is in a qualitative agreement with the recent ATLAS measurement of multi-particle azimuthal correlations with the subevent cumulant method.