# Quark Matter 2018

May 13 – 19, 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

## Measurements of the photo-production of jets in ultra-peripheral heavy ion collisions with the ATLAS detector at the LHC

May 15, 2018, 11:50 AM
20m
Sala Volpi, 1st Floor (Palazzo del Casinò)

### Sala Volpi, 1st Floor

#### Palazzo del Casinò

Parallel Talk Initial state physics and approach to equilibrium

### Speaker

Peter Alan Steinberg (Brookhaven National Laboratory (US))

### Description

Ultra-peripheral heavy ion collisions occur when the nuclei have large impact parameter and interact through photon-induced reactions. These include processes in which an energetic photon emitted by one nucleus resolves the partonic structure of the other and stimulates jet production. Much like deep inelastic scattering, such processes provide a clean probe of the nuclear parton distributions. This is in contrast to other observables in ion-ion and proton-ion collisions which typically involve the convolution of parton distributions in both incident particles. Thus jet photo-production represents the most direct opportunity to study nuclear parton distributions until a future electron-ion collider is constructed. This talk presents new measurements of ultra-peripheral jet photo-production in Pb+Pb collisions with the ATLAS detector at the LHC. Events are selected using a combination of forward neutron and rapidity gap requirements. Final states with two or more jets are used to construct event level observables $H_{\mathrm{T}}$, $x_{\mathrm{A}}$ and $z_{\gamma}$, which characterize the hard scattering process. Measurements of differential cross sections in these three quantities, after unfolding for detector response, are presented. The results are compared with theoretical calculations using different nPDF parameterizatinos, which highlight the potential of this data in future global analysis for precision nPDF determination.

Collaboration ATLAS Experiment Presenter name already specified

### Primary author

Barbara Krystyna Wosiek (Institute of Nuclear Physics Polish Academy of Sciences (PL))