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

TL;DR

This paper reports a search for heavy neutrinos and third-generation leptoquarks in proton-proton collisions at 13 TeV, using events with tau leptons and jets, setting new exclusion limits on their masses.

Contribution

It presents the first collider search for third-generation Majorana neutrinos and leptoquarks in final states with hadronically decaying tau leptons and jets.

Findings

Excluded W_R boson masses below 2.35 TeV for certain model assumptions.

Excluded third-generation scalar leptoquarks below 740 GeV.

First collider search for these particles in this specific final state.

Abstract

A search for new particles has been conducted using events with two high transverse momentum (pt) tau leptons that decay hadronically, at least two high-pt jets, and missing transverse energy from the tau lepton decays. The analysis is performed using data from proton-proton collisions, collected by the CMS experiment in 2015 at sqrt(s) = 13 TeV, corresponding to an integrated luminosity of 2.1 inverse femtobarns. The results are interpreted in two physics models. The first model involves heavy right-handed neutrinos, N[l] (l = e, mu, tau), and right-handed charged bosons, W[R], arising in a left-right symmetric extension of the standard model. Masses of the W[R] boson below 2.35 (1.63) TeV are excluded at 95% confidence level, assuming the N[tau] mass is 0.8 (0.2) times the mass of the W[R] boson and that only the N[tau] flavor contributes to the W[R] decay width. In the second model, pair production of third-generation scalar leptoquarks that decay into tau tau bb is considered. Third-generation scalar leptoquarks with masses below 740 GeV are excluded, assuming a 100% branching fraction for the leptoquark decay to a tau 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 tau leptons and jets.