# 10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

May 31, 2020 to June 5, 2020
Online
US/Central timezone

## Light-by-light scattering in ultra-peripheral Pb+Pb collisions in the ATLAS experiment

Jun 2, 2020, 7:30 AM
1h 20m
Online

#### Online

Poster Initial State

### Speaker

Klaudia Maj (AGH University of Science and Technology (PL))

### Description

The ultra-peripheral Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV performed at the ATLAS experiment are used to study a rare light-by-light scattering process,
$\gamma\gamma\rightarrow\gamma\gamma$, allowed in Quantum Electrodynamics via a loop
diagram. The poster summarises recent light-by-light measurements conducted using a combination of 2015 and 2018 datasets recorded by the ATLAS experiment, corresponding to an integrated luminosity of 2.2 n$b^{-1}$. The light-by-light event candidates are required to consist of only two photons produced exclusively, each with transverse energy $E_{\mathrm{T}} >$ 2.5 GeV, pseudorapidity $|\eta| <2.4$, diphoton invariant mass $m_{\gamma\gamma} > 5$ GeV, and with diphoton transverse momentum $p_{\mathrm{T}^{\gamma\gamma}}$ < 1 GeV and acoplanarity below 0.01. The differential distributions, presented as functions of kinematic and angular variables of the final-state photons, are unfolded for detector effects. The fiducial and differential cross-sections are presented and compared with theoretical predictions. The diphoton invariant mass distribution is
used to set limits on the production of axion-like particles.

Track Initial State Poster ATLAS

### Primary authors

Lidija Zivkovic (Institute of physics Belgrade (RS))

### Presentation materials

 HP poster session Klaudia Maj Poster ID = 283 KMaj-poster-LbyL.pdf