# Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC

## TL;DR

This paper investigates how fluctuating proton shapes influence flow observables in proton-lead collisions at the LHC, using a combined classical Yang-Mills and hydrodynamic model constrained by HERA data.

## Contribution

It demonstrates the critical role of sub-nucleon scale proton shape fluctuations in describing flow measurements, with shapes constrained by experimental data rather than free parameters.

## Key findings

- Proton shape fluctuations significantly affect azimuthal harmonic coefficients.
- Inclusion of temperature-dependent viscosities improves agreement with data.
- Results include detailed flow coefficients and HBT radii for charged and identified particles.

## Abstract

Results for particle production in root-s = 5.02 TeV p+Pb collisions at the Large Hadron Collider within a combined classical Yang-Mills and relativistic viscous hydrodynamic calculation are presented. We emphasize the importance of sub-nucleon scale fluctuations in the proton projectile to describe the experimentally observed azimuthal harmonic coefficients, demonstrating their sensitivity to the proton shape. We stress that the proton shape and its fluctuations are not free parameters in our calculations. Instead, they have been constrained using experimental data from HERA on exclusive vector meson production. Including temperature dependent shear and bulk viscosities, as well as UrQMD for the low temperature regime, we present results for mean transverse momenta, harmonic flow coefficients for charged hadrons and identified particles, as well as Hanbury-Brown-Twiss radii.