Search for type-III seesaw heavy leptons in dilepton final states in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Abstract

A search for the pair production of heavy leptons as predicted by the type-III seesaw mechanism is presented. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to 139 fb${}^{-1}$ of integrated luminosity recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis focuses on the final state with two light leptons (electrons or muons) of different flavour and charge combinations, with at least two jets and large missing transverse momentum. No significant excess over the Standard Model expectation is observed. The results are translated into exclusion limits on heavy-lepton masses, and the observed lower limit on the mass of the type-III seesaw heavy leptons is 790 GeV at 95% confidence level.

42 pages in total, author list starting page 26, 7 figures, 3 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-2018-33/

References in corpus (17)

• 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
• New parton distributions for collider physics
• Event generation with SHERPA 1.1
• Herwig++ Physics and Manual
• LHAPDF6: parton density access in the LHC precision era
• Parton distributions in the LHC era: MMHT 2014 PDFs
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Pileup subtraction using jet areas
• Electron and photon performance measurements with the ATLAS detector using the 2015-2017 LHC proton-proton collision data
• Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data
• HistFitter software framework for statistical data analysis
• Type-III see-saw at LHC
• Search for anomalous production of prompt same-sign lepton pairs and pair-produced doubly charged Higgs bosons with $\sqrt{s}=8$ TeV $pp$ collisions using the ATLAS detector
• Search for physics beyond the standard model in multilepton final states in proton-proton collisions at $\sqrt{s}=$ 13 TeV

Cited by in corpus (26)

• The Present and Future Status of Heavy Neutral Leptons
• Muon $g-2$ in two Higgs doublet models with vectorlike leptons
• $(\mathbf{g}-2{)}_{\mathbf{e},\mathbf{\mu }}$ in an extended inverse type-III seesaw
• Bounds on the triplet fermions in type-III seesaw and implications for collider searches
• Majorana Neutrinos in Same-Sign $W^{\pm }{W}^{\pm }$ Scattering at the LHC: Breaking the TeV Barrier
• A complete effective field theory for dark matter
• Exploration at the high-energy frontier: ATLAS Run~2 searches investigating the exotic jungle beyond the Standard Model
• Highly enhanced contributions of heavy Higgs bosons and new leptons to muon $g-2$ and prospects at future colliders
• Leptonic anomalous magnetic moments in $\nu$SMEFT
• Search for heavy Majorana or Dirac neutrinos and right-handed $W$ gauge bosons in final states with charged leptons and jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Type-III see-saw: Search for triplet fermions in final states with multiple leptons and fat-jets at 13 TeV LHC
• Displaced Higgs production in Type-III Seesaw at the LHC/FCC, MATHUSLA and Muon collider
• Probing HNL-ALP couplings at colliders
• Distinguishing Leptoquarks at the LHC/FCC
• Lowering the scale of fermion triplet leptogenesis with two Higgs doublets
• Search for new phenomena in three- or four-lepton events in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
• Current Status of the Muon g-2 Interpretations within Two-Higgs-Doublet Models
• CP violating dark photon kinetic mixing and type-III seesaw model
• H Marks the Spot: Searching for Exotic Production of Higgs + X to Map Out New Physics
• Verifiable type-III seesaw and dark matter in a gauged $\mathbf{U}(1{)}_{\mathrm{B}-\mathrm{L}}$ symmetric model
• TeV Scale Resonant Leptogenesis with triplet Fermion in Connection to Muon $g-2$
• Seesaw Models under the Lens of Angular Distributions at ${\mu }^{+}{\mu }^{-},{\mu }^{+}{\mu }^{+},{\mu }^{+}\gamma$ and ${\mu }^{+}{e}^{-}$ Colliders
• Minimal dark matter in $SU(5)$ grand unification
• Searches for New High-Mass Resonances Decaying to Fermions at the LHC
• Radiative neutrino masses: A window to new physics
• Type-III Scotogenic Model: Inflation, Dark Matter and Collider Phenomenology