# Accessing the gluon Wigner distribution in ultraperipheral $pA$ collisions

## TL;DR

This paper proposes a method to measure the gluon Wigner distribution in nucleons through exclusive diffractive dijet production in ultraperipheral proton-nucleus collisions at RHIC and LHC, highlighting advantages over previous lepton-nucleon scattering approaches.

## Contribution

It introduces a novel approach using ultraperipheral collisions to access the gluon Wigner distribution, simplifying extraction and including saturation effects in the models.

## Key findings

- Cross section calculations for the process.
- Evaluation of angular dependence of the distribution.
- Discussion on experimental feasibility at RHIC and LHC.

## Abstract

We propose to constrain the gluon Wigner distribution in the nucleon by studying the exclusive diffractive dijet production process in ultraperipheral proton-nucleus collisions (UPCs) at RHIC and the LHC. Compared to the previous proposal in Ref. [Y. Hatta, B. W. Xiao, and F. Yuan, Phys. Rev. Lett. 116, 202301 (2016).] to study the same observable in lepton-nucleon scattering, the use of UPCs has a few advantages: not only is the cross section larger, but the extraction of the Wigner distribution from the data also becomes simpler, including its elliptic angular dependence. We compute the corresponding cross section and evaluate the coefficients using models which include the gluon saturation effects. A potential for the measurements of the Wigner distribution at current and future experimental facilities is also discussed.