Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying into invisible particles at 13 TeV with the ATLAS detector

Abstract

This paper presents a measurement of the electroweak production of two jets in association with a $Z\gamma$ pair, with the $Z$ boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector and corresponding to an integrated luminosity of 139 fb${}^{-1}$. The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak $Z\gamma$ production in association with two jets is observed in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31$\pm$0.29 fb. An observed (expected) upper limit of 0.37 ($0.34_{-0.10}^{+0.15}$) at 95% confidence level is set on the branching ratio of a 125 GeV Higgs boson to invisible particles, assuming the Standard Model production cross-section. The signature is also interpreted in the context of decays of a Higgs boson into a photon and a dark photon. An observed (expected) 95% CL upper limit on the branching ratio for this decay is set at 0.018 ($0.017_{-0.005}^{+0.007}$), assuming the Standard Model production cross-section for a 125 GeV Higgs boson.

58 pages in total, author list starting page 42, 9 figures, 7 tables. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2021-17/

References in corpus (20)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Herwig++ Physics and Manual
• Parton distributions in the LHC era: MMHT 2014 PDFs
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Tuning PYTHIA 8.1: the Monash 2013 Tune
• An NNLO subtraction formalism in hadron collisions and its application to Higgs boson production at the LHC
• Higgs boson gluon-fusion production in N3LO QCD
• NLO Electroweak Corrections to Higgs Boson Production at Hadron Colliders
• Muon reconstruction and identification efficiency in ATLAS using the full Run 2 $pp$ collision data set at $\sqrt{s}=13$ TeV
• Dark matter and the early Universe: a review
• Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes
• Top mass effects in Higgs production at next-to-next-to-leading order QCD: virtual corrections
• Searches for invisible decays of the Higgs boson in pp collisions at sqrt(s) = 7, 8, and 13 TeV
• p p -> j j e+/- mu+/- nu nu and j j e+/- mu-/+ nu nu at O(α_{em}^6) and O(α_{em}^4 α_s^2) for the Study of the Quartic Electroweak Gauge Boson Vertex at LHC
• Dark photons and resonant monophoton signatures in Higgs boson decays at the LHC
• Isolating Vector Boson Scattering at the LHC: gauge cancellations and the Equivalent Vector Boson Approximation vs complete calculations
• Higgs Boson Production in Association with a Photon in Vector Boson Fusion at the LHC
• Search for chargino-neutralino production in events with Higgs and W bosons using 137 fb${}^{-1}$ of proton-proton collisions at $\sqrt{s}=$ 13 TeV

Cited by in corpus (11)

• Search for invisible Higgs-boson decays in events with vector-boson fusion signatures using 139 ${\text{fb}}^{-1}$ of proton-proton data recorded by the ATLAS experiment
• Exploration at the high-energy frontier: ATLAS Run~2 searches investigating the exotic jungle beyond the Standard Model
• Exotic Higgs Decays
• Electroweak, QCD and flavour physics studies with ATLAS data from Run 2 of the LHC
• Is the decay of the Higgs boson to a photon and a dark photon currently observable at the LHC?
• Observability of the Higgs boson decay to a photon and a dark photon
• Combination and summary of ATLAS dark matter searches interpreted in a 2HDM with a pseudo-scalar mediator using 139 fb${}^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data
• Semi-dark Higgs decays: sweeping the Higgs neutrino floor
• Limiting the Heavy-quark and Gluon-philic Real Dark Matter
• Illuminating all-hadronic final states with a photon: Exotic decays of the Higgs boson to four bottom quarks in vector boson fusion plus gamma at hadron colliders
• Dark photon searches via Higgs boson production at the LHC and beyond