Search for type-III seesaw heavy leptons in pp collisions at √s= 8 TeV with the ATLAS detector

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Allbrooke, Benedict ; Asquith, Lily ; Cerri, Alessandro ; Chavez Barajas, Carlos ; De Santo, Antonella ; Potter, Tina ; Salvatore, Fabrizio ; Santoyo Castillo, Itzebelt ; Suruliz, Kerim ; Sutton, Mark ; Vivarelli, Iacopo ; The ATLAS Collaboration, et al (2015)

A 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.
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