Observation of Light-by-Light Scattering in Ultraperipheral Pb plus Pb Collisions with the ATLAS Detector
Date
2019
Authors
Aad, G.
Abbott, B.
Abbott, D.
Abdinov, O.
Abud, A.A.
Abeling, K.
Abhayasinghe, D.
Abidi, S.
AbouZeid, O.
Abraham, N.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
PHYSICAL REVIEW LETTERS, 2019; 123(5)
Statement of Responsibility
Conference Name
Abstract
This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at sqrt[s_{NN}]=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 E_{T}^{γ}>3 GeV and pseudorapidity |η_{γ}|<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.