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$$ \sqrt{s}=13 $$ TeV

Abstract

A search for new particles has been conducted using events with two high transverse momentum (pT) τ leptons that decay hadronically, at least two high-pT 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 W[subscript R] boson below 2.35 (1.63) TeV are excluded at 95% confidence level, assuming the N[subscript τ]mass is 0.8 (0.2) times the mass of the W[subscript R] boson and that only the N[subscript τ]flavor contributes to the W[subscript R]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. Keywords: Beyond Standard Model; Hadron-Hadron scattering (experiments); protonproton scattering