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 $|m_{\mu \mu }|$.

arXiv comment37 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 (57)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• The anti-k_t jet clustering algorithm
• An Introduction to PYTHIA 8.2
• A Brief Introduction to PYTHIA 8.1
• FastJet user manual
• Parton distributions for the LHC
• Asymptotic formulae for likelihood-based tests of new physics
• Direct Evidence for Neutrino Flavor Transformation from Neutral-Current Interactions in the Sudbury Neutrino Observatory
• A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX
• A New Method for Combining NLO QCD with Shower Monte Carlo Algorithms
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• FeynRules 2.0 - A complete toolbox for tree-level phenomenology
• Parton distributions for the LHC Run II
• Matching NLO QCD computations and parton shower simulations
• The ATLAS Simulation Infrastructure
• Confidence Level Computation for Combining Searches with Small Statistics
• Scattering Amplitudes with Open Loops
• Herwig 7.0 / Herwig++ 3.0 Release Note
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• QCD Matrix Elements + Parton Showers
• Comix, a new matrix element generator
• Event Generation with Sherpa 2.2
• QCD matrix elements + parton showers: The NLO case
• Performance of the ATLAS Trigger System in 2015
• The Search for Heavy Majorana Neutrinos
• A Measurement of Atmospheric Neutrino Oscillation Parameters by Super-Kamiokande I
• QCD matrix elements and truncated showers
• Collier: a fortran-based Complex One-Loop LIbrary in Extended Regularizations
• Pathways to Naturally Small Neutrino Masses
• Muon reconstruction performance of the ATLAS detector in proton--proton collision data at $\sqrt{s}$=13 TeV
• Neutrinoless Double-Beta Decay: Status and Prospects
• A critical appraisal of NLO+PS matching methods
• Production and Integration of the ATLAS Insertable B-Layer
• OpenLoops 2
• Performance of pile-up mitigation techniques for jets in $pp$ collisions at $\sqrt{s}=8$ TeV using the ATLAS detector
• Neutrinos and Collider Physics
• Electron and photon performance measurements with the ATLAS detector using the 2015-2017 LHC proton-proton collision data
• ATLAS $b$-jet identification performance and efficiency measurement with $t\bar{t}$ events in $pp$ collisions at $\sqrt{s}=13$ TeV
• Jet reconstruction and performance using particle flow with the ATLAS Detector
• 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
• Performance of missing transverse momentum reconstruction with the ATLAS detector using proton-proton collisions at $\sqrt{s}$ = 13 TeV
• 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
• Single-top t-channel hadroproduction in the four-flavour scheme with POWHEG and aMC@NLO
• A comprehensive approach to new physics simulations
• Search for heavy neutral leptons in events with three charged leptons in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at $\sqrt{s}=8$ TeV
• Search for heavy neutral leptons in decays of $W$ bosons produced in 13 TeV $pp$ collisions using prompt and displaced signatures with the ATLAS detector
• Fully-Automated Precision Predictions for Heavy Neutrino Production Mechanisms at Hadron Colliders
• Heavy Majorana Neutrinos from $W\gamma$ Fusion at Hadron Colliders
• Search for heavy Majorana neutrinos in same-sign dilepton channels in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• Some Dipole Shower Studies
• 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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