# Proton structure fluctuations: from HERA to the LHC

## TL;DR

This paper investigates proton shape fluctuations by analyzing HERA diffractive data and incorporates these fluctuations into hydrodynamical models to successfully describe LHC proton-nucleus collision results.

## Contribution

It constrains proton shape fluctuations using HERA data and applies these constraints to hydrodynamical simulations of proton-nucleus collisions at the LHC.

## Key findings

- HERA data favor large geometric proton fluctuations
- Fluctuating proton shapes improve hydrodynamical model agreement with LHC data
- Successful description of mean transverse momentum and flow harmonics

## Abstract

We constrain the amount of event-by-event fluctuations of the proton by comparing with the HERA coherent and incoherent diffractive $J/\Psi$ production data. We find that the HERA measurements prefer large geometric fluctuations. We then include the constrained fluctuating proton shapes in viscous hydrodynamical simulations of the proton-nucleus collisions at $\sqrt{s_{NN}}=5.02$ TeV, and find a good description of the mean transverse momentum and flow harmonics measured at the LHC.