Search for heavy neutral leptons in decays of W bosons produced in 13 TeV pp collisions using prompt signatures in the ATLAS detector

Abstract

The existence of right-handed neutrinos with Majorana masses below the electroweak scale could help address the origins of neutrino masses, the matter-antimatter asymmetry, and dark matter. In this paper, leptonic decays of W bosons from 140 fb${}^{-1}$ of 13 TeV proton-proton collisions at the LHC, reconstructed in the ATLAS experiment, are used to search for heavy neutral leptons produced through their mixing with muon or electron neutrinos in a scenario with lepton number violation. The search is conducted using prompt leptonic decay signatures. The considered final states require two same-charge leptons or three leptons, while vetoing three-lepton same-flavour topologies. No significant excess over the expected Standard Model backgrounds is found, leading to constraints on the heavy neutral lepton's mixing with muon and electron neutrinos for heavy-neutral-lepton masses. The analysis excludes $|U_e{|}^2$ values above $8\times 10^{-5}$ and $|U_{\mu }{|}^2$ values above $5.0\times 10^{-5}$ in the full mass range of 8-65 GeV. The strongest constraints are placed on heavy-neutral-lepton masses in the range 15-30 GeV of $|U_e{|}^2<1.1\times 10^{-5}$ and $|U_{\mu }{|}^2<5\times 10^{-6}$.

44 pages in total, author list starting page 27, 4 figures, 5 tables, published in Eur. Phys. J. C.. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2019-35/

References in corpus (43)

• 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
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Leptogenesis
• Single-top Wt-channel production matched with parton showers using the POWHEG method
• Single-top hadroproduction in association with a W boson
• Right-Handed Neutrinos at LHC and the Mechanism of Neutrino Mass Generation
• Muon reconstruction and identification efficiency in ATLAS using the full Run 2 $pp$ collision data set 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
• How to find neutral leptons of the nuMSM?
• HistFitter software framework for statistical data analysis
• A possible symmetry of the $\nu$MSM
• The PDF4LHC21 combination of global PDF fits for the LHC Run III
• Luminosity determination in $pp$ collisions at $\sqrt{s}=13$ TeV using the ATLAS detector at the LHC
• ATLAS flavour-tagging algorithms for the LHC Run 2 $pp$ collision dataset
• Heavy Majorana Neutrinos from $W\gamma$ Fusion at Hadron Colliders
• Measurement of the $c$-jet mistagging efficiency in $t\bar{t}$ events using $pp$ collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector
• Evidence for $t\bar{t}t\bar{t}$ production in the multilepton final state in proton-proton collisions at $\sqrt{s}$=13 TeV with the ATLAS detector
• Performance of the ATLAS muon trigger in pp collisions at $\sqrt{s}=8$ TeV
• Calibration of the light-flavour jet mistagging efficiency of the $b$-tagging algorithms with $Z$+jets events using 139 ${\mathrm{fb}}^{-1}$ of ATLAS proton-proton collision data at $\sqrt{s}=13$ TeV
• The Little Review on Leptogenesis
• Higher-order corrections for $tW$ production at high-energy hadron colliders
• Search for long-lived heavy neutral leptons with displaced vertices in proton-proton collisions at $\sqrt{s}=$ 13 TeV
• 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
• Single-top-quark production in the $t$-channel at NNLO
• Reinterpreting the ATLAS bounds on heavy neutral leptons in a realistic neutrino oscillation model
• Alignment of the ATLAS Inner Detector in Run-2
• Sterile neutrino dark matter via coinciding resonances
• Search for heavy neutral leptons in decays of $W$ bosons using a dilepton displaced vertex in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Electron and photon efficiencies in LHC Run 2 with the ATLAS experiment
• Search for heavy neutral leptons in $W^{+}\to {\mu }^{+}{\mu }^{\pm }\text{jet}$ decays
• Tools for estimating fake/non-prompt lepton backgrounds with the ATLAS detector at the LHC
• Search for heavy neutral leptons in final states with electrons, muons, and hadronically decaying tau leptons in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• Search for Majorana neutrinos in same-sign $WW$ scattering events from $pp$ collisions at $\sqrt{s}=13$ TeV
• Electron and photon energy calibration with the ATLAS detector using LHC Run 2 data
• The performance of missing transverse momentum reconstruction and its significance with the ATLAS detector using 140 fb${}^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collisions
• Search for heavy Majorana neutrinos in $e^{\pm }{e}^{\pm }$ and $e^{\pm }{\mu }^{\pm }$ final states via WW scattering in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Search for heavy neutral leptons in decays of W bosons using leptonic and semi-leptonic displaced vertices in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector
• Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton
• Search for pair production of squarks or gluinos decaying via sleptons or weak bosons in final states with two same-sign or three leptons with the ATLAS detector

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