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

A search for the pair production of heavy leptons (N 0, L $\pm$) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N 0 → W $\pm$ l□(ℓ = e, μ, τ) and L $\pm$ → W $\pm$ ν (ν = ν e, ν μ, ν τ) 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 p p 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. \copyright 2015 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the "http://creativecommons.org/licenses/by/3.0/" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.