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arXiv · 2103.10322

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

ATLAS Collaboration
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Abstract

A search for the Higgs boson decaying into a photon and a pair of electrons or muons with an invariant mass $m_{\ell\ell} < 30$ 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 $H \rightarrow \ell \ell γ$ process is found with a significance of 3.2$σ$ over the background-only hypothesis, compared to an expected significance of 2.1$σ$. 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 $μ= 1.5 \pm 0.5$. The Higgs boson production cross-section times the $H \rightarrow\ell\ellγ$ branching ratio for $m_{\ell\ell} <$ 30 GeV is determined to be 8.7 $^{+2.8}_{-2.7}$ fb.

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ATLAS Collaboration. 2021-06-14. Evidence for Higgs boson decays to a low-mass dilepton system and a photon in pp collisions at $\sqrt{s} =$ 13 TeV with the ATLAS detector. https://doi.org/10.1016/j.physletb.2021.136412

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