Search for Majorana neutrinos in same-sign $WW$ scattering events from $pp$ collisions at $\sqrt{s}=13$ TeV

Abstract

A search for Majorana neutrinos in same-sign $WW$ scattering events is presented. The analysis uses $\sqrt{s}=13$ TeV proton-proton collision data with an integrated luminosity of 140 fb${}^{-1}$ recorded during 2015-2018 by the ATLAS detector at the Large Hadron Collider. The analysis targets final states including exactly two same-sign muons and at least two hadronic jets well separated in rapidity. The modelling of the main backgrounds, from Standard Model same-sign $WW$ scattering and $WZ$ production, is constrained with data in dedicated signal-depleted control regions. The distribution of the transverse momentum of the second-hardest muon is used to search for signals originating from a heavy Majorana neutrino with a mass between 50 GeV and 20 TeV. No significant excess is observed over the background expectation. The results are interpreted in a benchmark scenario of the Phenomenological Type-I Seesaw model. In addition, the sensitivity to the Weinberg operator is investigated. Upper limits at the 95% confidence level are placed on the squared muon-neutrino-heavy-neutrino mass-mixing matrix element $|V_{\mu N}{|}^2$ as a function of the heavy Majorana neutrino's mass $m_N$, and on the effective $\mu \mu$ Majorana neutrino mass $|m_{\mu \mu }|$.

37 pages in total, author list starting page 19, 3 figures, 1 table. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2020-06/

References in corpus (14)

• 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
• Parton distributions for the LHC
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Distinguishing seesaw models at LHC with multi-lepton signals
• Muon reconstruction and identification efficiency in ATLAS using the full Run 2 $pp$ collision data set at $\sqrt{s}=13$ TeV
• From the trees to the forest: a review of radiative neutrino mass models
• Automation of next-to-leading order computations in QCD: the FKS subtraction
• Jet energy scale and resolution measured in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Performance of the ATLAS muon triggers in Run 2
• Heavy Majorana Neutrinos from $W\gamma$ Fusion at Hadron Colliders
• Probing the Weinberg Operator at Colliders
• Majorana Neutrinos in Same-Sign $W^{\pm }{W}^{\pm }$ Scattering at the LHC: Breaking the TeV Barrier

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• Future collider sensitivities to $\nu$SMEFT interactions
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