Search for Type III Seesaw Heavy Leptons in proton-proton collisions with the ATLAS detector at the LHC

A search for pair-production of heavy leptons ($\Sigma^{0}$, $\Sigma^{\pm}$)predicted by the Type III seesaw mechanism to explain the origin of small neutrino masses is presented. The decay channels for the heavy leptons $\Sigma^0\rightarrow W^{\pm}e^{\mp}$ and $\Sigma^{\pm} \rightarrow W^{\pm}\nu_{e}$ are considered. Multivariate techniques versus a kinematic selection method are compared. The study is based on proton-proton collisions recorded at the ATLAS detector at the Large Hadron Collider at CERN during 2015 with a center-of-mass energy of 13 TeV. The data used corresponds to an integrated luminosity of 3.2 fb$^{-1}$ and no evidence of heavy lepton pair-production was observed.