Aad, G.Abbott, B.Abdallah, J.Abdinov, O.Aben, R.Abolins, M.AbouZeid, O. S.Izen, Joseph M.Leyton, MichaelMeirose, BernhardNamasivayam, HarisankarReeves, KendallATLAS Collaboration2016-12-162016-12-162015-08-012015-08-011550-7998http://hdl.handle.net/10735.1/5168A search for the pair production of heavy leptons (N⁰,L^±) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N⁰→W^±l^∓ (ℓ=e,μ,τ) and L^±→W^±ν {(ν=νe,νμ,ντ)} are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3 fb⁻¹ of pp collisions at √s = 8  TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair production is observed. Heavy leptons with masses below 325–540 GeV are excluded at the 95% confidence level, depending on the theoretical scenario considered.enCC BY 3.0 (Attribution)©2015 CERN, for the ATLAS Collaborationhttp://creativecommons.org/licenses/by/3.0/NeutrinosHeavy leptons (Nuclear physics)Transverse momentumJets (Nuclear physics)Causality (Physics)Proton-proton interactionsElectronsMuonsBosonsArticleAad, G., B. Abbott, J. Abdallah, O. Abdinov, et al. 2015. "Search for type-III seesaw heavy leptons in pp collisions at root s=8 TeV with the ATLAS detector." Physical Review D 92(3), doi: 10.1103/PhysRevD.92.032001923