Mapping the Proton's Fluctuating Waistline

TL;DR

This paper proposes that rare fluctuations in the proton's shape, such as a 'fat' proton, can explain universal scaling in high-energy nuclear collision particle distributions and influence initial state geometry.

Contribution

It introduces simple models of proton shape fluctuations to explain universal scaling and their effects on nuclear collision initial conditions.

Findings

Rare proton shape fluctuations occur with observable frequency.

Proton fluctuations influence initial spatial eccentricities in nuclear collisions.

Model suggests collective flow behavior is feasible due to these fluctuations.

Abstract

We discuss a mechanism for the apparently universal scaling in the high-multiplicity tail of charged particle distributions for high energy nuclear collisions. We argue that this scaling behavior originates from rare fluctuations of the nucleon density. We discuss a pair of simple models of proton shape fluctuations. A "fat" proton with a size of 3 fm occurs with observable frequency. In light of this result, collective flow behavior in the ensuing nuclear interaction seems feasible. We discuss the influence of these models on the large $x$ structure of the proton and the likely influences on the distribution of initial state spatial eccentricities $\epsilon_{n}$.