Search for the Higgs boson decay to a $Z$ boson and a photon in $pp$ collisions at $\sqrt{s}=13$ TeV and $13.6$ TeV with the ATLAS detector

Abstract

A search for the Higgs boson decay to a $Z$ boson and a photon in the $\ell \ell \gamma$ ($\ell =e,\mu$) final state is performed using $pp$ collisions at $\sqrt{s}=13.6$ TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022-2024, corresponding to an integrated luminosity of 165 fb${}^{-1}$. The signal yield, normalised to the Standard Model prediction, is measured to be $\mu =0.9_{-0.6}^{+0.7}$, compared to an expected value of $\mu =1.0\pm 0.7$. This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations for the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb${}^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collisions to provide the most stringent expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of $\mu =1.3_{-0.5}^{+0.6}$ ($\mu =1.0_{-0.5}^{+0.6}$), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation.

43 pages in total, author list starting page 26, 4 figures, 4 tables. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGP-2024-19

References in corpus (27)

• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Higgs boson gluon-fusion production in N3LO QCD
• NLO Electroweak Corrections to Higgs Boson Production at Hadron Colliders
• A portrait of the Higgs boson by the CMS experiment ten years after the discovery
• Electroweak and QCD corrections to Higgs production via vector-boson fusion at the LHC
• A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery
• Muon reconstruction and identification efficiency in ATLAS using the full Run 2 $pp$ collision data set at $\sqrt{s}=13$ TeV
• Strong and electroweak corrections to the production of Higgs+2jets via weak interactions at the LHC
• Jet energy scale and resolution measured in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Higgs boson production in association with top quarks in the POWHEG BOX
• vh@nnlo - Higgs Strahlung at hadron colliders
• The PDF4LHC21 combination of global PDF fits for the LHC Run III
• Top mass effects in Higgs production at next-to-next-to-leading order QCD: virtual corrections
• QCD NLO and EW NLO corrections to $t\bar{t}H$ production with top quark decays at hadron collider
• Soft gluon resummation for gluon-induced Higgs Strahlung
• Higgs production in association with bottom quarks
• AtlFast3: the next generation of fast simulation in ATLAS
• Higgs boson decays to $\gamma \gamma$ and $Z\gamma$ in models with Higgs extensions
• A Novel Technique for Studying the Z Boson Transverse Momentum Distribution at Hadron Colliders
• Software and computing for Run 3 of the ATLAS experiment at the LHC
• Studies of the muon momentum calibration and performance of the ATLAS detector with $pp$ collisions at $\sqrt{s}$=13 TeV
• Measurement of the properties of Higgs boson production at $\sqrt{s}=13$ TeV in the $H\to \gamma \gamma$ channel using $139$ fb${}^{-1}$ of $pp$ collision data with the ATLAS experiment
• Electron and photon efficiencies in LHC Run 2 with the ATLAS experiment
• Search for Higgs boson decays to a Z boson and a photon in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• The SM expected branching ratio for $h\to \gamma \gamma$ and an excess for $h\to Z\gamma$