Trilepton signals: the golden channel for seesaw searches at LHC

Abstract

The comparison of samples with different number of charged leptons shows that trilepton signals are the most significant ones for seesaw mediators. As previously pointed out, this is indeed the case for scalar Δ (type II) and fermion Σ (type III) triplets at LHC, which can be discovered in this channel for masses up to 500–700 GeV and an integrated luminosity of 30 fb−1; whereas fermion singlets N (type I) are marginally observable if there are no further new physics near the TeV scale. However, if there are new gauge interactions at this scale coupling to right-handed neutrinos, as in left–right models, heavy neutrinos are observable up to masses ∼ 2 TeV for new gauge boson masses up to ∼ 4 TeV, as we discuss in some detail.