# Multiparticle collectivity from initial state correlations in high energy proton-nucleus collisions

## TL;DR

This paper presents an initial state model that reproduces key multiparticle correlation features in high-energy proton-nucleus collisions, offering an alternative to hydrodynamic explanations.

## Contribution

It introduces a simple initial state framework that captures multiparticle correlation patterns traditionally attributed to collective flow.

## Key findings

- Reproduces azimuthal harmonic ordering in $p+A$ collisions
- Matches energy and momentum dependence of $v_2 ext{ }{4}$
- Shows similar correlation patterns in an Abelian model

## Abstract

Qualitative features of multiparticle correlations in light-heavy ion ($p+A$) collisions at RHIC and LHC are reproduced in a simple initial state model of partons in the projectile coherently scattering off localized domains of color charge in the heavy nuclear target. These include i) the ordering of the magnitudes of the azimuthal angle $n$th Fourier harmonics of two-particle correlations $v_n\{2\}$, ii) the energy and transverse momentum dependence of the four-particle Fourier harmonic $v_2\{4\}$, and iii) the energy dependence of four-particle symmetric cumulants measuring correlations between different Fourier harmonics. Similar patterns are seen in an Abelian version of the model, where we observe $v_2\{2\} > v_2\{4\}\approx v_2\{6\}\approx v_2\{8\}$ of two, four, six, and eight particle correlations. While such patterns are often interpreted as signatures of collectivity arising from hydrodynamic flow, our results provide an alternative description of the multiparticle correlations seen in $p+A$ collisions.