A scaling relation between proton-nucleus and nucleus-nucleus collisions

TL;DR

This paper demonstrates that proton-nucleus ($pA$) collisions exhibit flow phenomena similar to nucleus-nucleus ($AA$) collisions at the same multiplicity, using a simple conformal scaling model based on cluster fluctuations.

Contribution

It introduces a conformal scaling model that explains $pA$ flow phenomena as a collective response to cluster fluctuations, aligning $pA$ and $AA$ collision behaviors.

Findings

The model reproduces elliptic and triangular flow in $pA$ collisions.

Flow in $pA$ arises from fluctuations in cluster positions.

Scaling relations unify $pA$ and $AA$ collision data.

Abstract

It is recently discovered that at high multiplicy, the proton-nucleus ($pA$) collisions give rise to two particle correlations that are strikingly similar to those of nucleus-nucleus ($AA$) collisions at the same multiplicity, although the system size is smaller in $pA$. Using an independent cluster model and a simple conformal scaling argument, where the ratio of the mean free path to the system size stays constant at fixed multiplicity, we argue that flow in $pA$ emerges as a collective response to the fluctuations in the position of clusters, just like in $AA$ collisions. With several physically motivated and parameter free rescalings of the recent LHC data, we show that this simple model captures the essential physics of elliptic and triangular flow in $pA$ collisions.