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


Aad G., Abbott B., Abbott D. C., Abdinov O., Abud A. A., Abeling K., ...More

PHYSICAL REVIEW LETTERS, vol.123, no.5, 2019 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 123 Issue: 5
  • Publication Date: 2019
  • Doi Number: 10.1103/physrevlett.123.052001
  • Journal Name: PHYSICAL REVIEW LETTERS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Istanbul University Affiliated: Yes

Abstract

This Letter describes the observation of the light-by-light scattering process, gamma gamma -> gamma gamma, in Pb + Pb collisions at root 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(gamma) > 3 GeV and pseudorapidity vertical bar eta(gamma)vertical bar < 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.