# Charged-particle angular correlations in XeXe collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.44 TeV

## TL;DR

This paper investigates azimuthal charged-particle correlations in xenon-xenon collisions at 5.44 TeV, comparing results with lead-lead data and hydrodynamic models to better understand the collective behavior in heavy ion collisions.

## Contribution

It provides the first detailed measurement of azimuthal anisotropy coefficients in XeXe collisions at the LHC, offering new insights into initial-state fluctuations and collective flow.

## Key findings

- Measured $v_2$, $v_3$, $v_4$ coefficients in XeXe collisions.
- Compared XeXe results with PbPb data and hydrodynamic models.
- Constraints on hydrodynamic descriptions of heavy ion collisions.

## Abstract

Azimuthal correlations of charged particles in xenon-xenon collisions at a center-of-mass energy per nucleon pair of $ \sqrt{s_{_\mathrm{NN}}} =$ 5.44 TeV are studied. The data were collected by the CMS experiment at the LHC with a total integrated luminosity of 3.42 $\mu$b$^{-1}$. The collective motion of the system formed in the collision is parameterized by a Fourier expansion of the azimuthal particle density distribution. The azimuthal anisotropy coefficients $v_{2}$, $v_{3}$, and $v_{4}$ are obtained by the scalar-product, two-particle correlation, and multiparticle correlation methods. Within a hydrodynamic picture, these methods have different sensitivities to non-collective and fluctuation effects. The dependence of the Fourier coefficients on the size of the colliding system is explored by comparing the xenon-xenon results with equivalent lead-lead data. Model calculations that include initial-state fluctuation effects are also compared to the experimental results. The observed angular correlations provide new constraints on the hydrodynamic description of heavy ion collisions.