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

Abstract

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 ¼ e; μ; τ) and L → W ν (ν ¼ 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 ffisffiffi p ¼ 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 GeVare excluded at the 95% confidence level, depending on the theoretical scenario considered.