Probing gluon saturation and nuclear structure in photon-nucleus collisions

TL;DR

This paper uses the Color Glass Condensate framework to predict nuclear suppression in vector meson photoproduction during ultra peripheral heavy ion collisions, revealing insights into gluon saturation and nuclear structure at high energies.

Contribution

It provides the first predictions of nuclear suppression effects in vector meson photoproduction at TeV energies constrained by HERA data, and explores how photon polarization reveals nuclear geometry details.

Findings

Significant nuclear suppression predicted at TeV energies.

LHC data suggests stronger saturation effects.

Photon polarization induces azimuthal modulations revealing nuclear deformation.

Abstract

We calculate exclusive vector meson photoproduction within the Color Glass Condensate framework in high-energy photon-nucleus scattering probed experimentally in ultra peripheral heavy ion collisions at RHIC and at the LHC. When the free parameters are constrained by the $\gamma+p$ data from HERA, we predict significant nuclear suppression for both the coherent and incoherent photoproduction cross section in the TeV range. Our results indicate that the LHC data prefers even stronger saturation effects at the highest collision energies. Furthermore, we demonstrate how the linear polarization of photons in ulra peripheral collisions generates azimuthal modulations in the decay products of the exclusively produced vector meson. We show how these measurements can probe details of the nuclear geometry, specifically the deformed structure of the uranium nuclei.