Search for heavy neutrinos or third-generation leptoquarks in final states with two hadronically decaying τ leptons and two jets in proton-proton collisions at √s=13 TeV

Abstract

A search for new particles has been conducted using events with two high transverse momentum (p T) τ leptons that decay hadronically, at least two high-p T jets, and missing transverse energy from the τ lepton decays. The analysis is performed using data from proton-proton collisions, collected by the CMS experiment in 2015 at √s=13 TeV, corresponding to an integrated luminosity of 2.1 fb−1. The results are interpreted in two physics models. The first model involves heavy right-handed neutrinos, Nℓ (ℓ = e, μ, τ), and right-handed charged bosons, WR, arising in a left-right symmetric extension of the standard model. Masses of the WR boson below 2.35 (1.63) TeV are excluded at 95% confidence level, assuming the N τ mass is 0.8 (0.2) times the mass of the WR boson and that only the N τ flavor contributes to the WR decay width. In the second model, pair production of third-generation scalar leptoquarks that decay into ττbb is considered. Third-generation scalar leptoquarks with masses below 740 GeV are excluded, assuming a 100% branching fraction for the leptoquark decay to a τ lepton and a bottom quark. This is the first search at hadron colliders for the third-generation Majorana neutrino, as well as the first search for third-generation leptoquarks in the final state with a pair of hadronically decaying τ leptons and jets.