Evidence for Higgs boson decays to a low-mass dilepton system and a photon in pp collisions at √s = 13 TeV with the ATLAS detector

Research output: Contribution to journalArticlepeer-review


  • ATLAS Collaboration

Colleges, School and Institutes


A search for the Higgs boson decaying into a photon and a pair of electrons or muons with an invariant mass mℓℓ < 30$ GeV is presented. The analysis is performed using 139 fb-1 of proton-proton collision data, produced by the LHC at a centre-of-mass energy of 13 TeV and collected by the ATLAS experiment. Evidence for the H → ℓℓγ process is found with a significance of 3.2 over the background-only hypothesis, compared to an expected significance of 2.1 for the Standard Model prediction. The best-fit value of the signal strength parameter, defined as the ratio of the observed signal yield to the one expected in the Standard Model, is μ = 1.5 ± 0.5. The Higgs boson production cross-section times the H → ℓℓγ branching ratio for mℓℓ < 30$ GeV is determined to be 8.7-2.7+2.8 fb.

Bibliographic note

39 pages in total, author list starting page 23, 5 figures, 1 table, submitted to PLB, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2018-43/


Original languageEnglish
Article number136412
Number of pages22
JournalPhys. Lett. B
Early online date31 May 2021
Publication statusPublished - 10 Aug 2021


  • hep-ex