Observation of Light-by-Light Scattering in Ultraperipheral Pb plus Pb Collisions with the ATLAS Detector

Aad, G, Abbott, B, Abbott, DC, Abdinov, O, Abud, A Abed, Abeling, K, Abhayasinghe, DK, Abidi, SH, AbouZeid, OS, Abraham, NL
et al (show 2920 more authors) (2019) Observation of Light-by-Light Scattering in Ultraperipheral Pb plus Pb Collisions with the ATLAS Detector. Physical Review Letters, 123 (5).

Access the full-text of this item by clicking on the Open Access link.

Abstract

This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at √sNN=5.02  TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73  nb−1, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy EγT>3  GeV and pseudorapidity |ηγ|<2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12±3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78±13(stat)±7(syst)±3(lumi)  nb.

Item Type: Article relativistic heavy-ion collisions Symplectic Admin 23 Sep 2019 08:05 18 May 2021 10:33 10.1103/PhysRevLett.123.052001 https://doi.org/10.1103/PhysRevLett.123.052001 Publisher https://livrepository.liverpool.ac.uk/id/eprint/3055604