Search for heavy neutrinos and third-generation leptoquarks in final states with two hadronically decaying $\tau$ leptons and two jets in proton-proton collisions at $\sqrt{s} = 13~\mathrm{TeV}$

A search for heavy, right-handed neutrinos, $N_{l}$, and right-handed $W_{R}$ bosons, which arise in the left-right symmetric extensions of the standard model, has been performed. The search focuses on the scenario where the $W_{R}$ and $N_{l}$ decay chains result in a pair of high-$p_{T}$ $\tau$ leptons which decay hadronically, in addition to two high-$p_{T}$ jets and missing transverse energy from the $\tau$ lepton decays. The analysis is performed using 2.1 $\rm fb^{-1}$ of data collected by the CMS experiment in 2015 at $\sqrt{s} = 13$ TeV. For models with strict left-right symmetry, and assuming only $N_{\tau}$ flavor contributes significantly to the $W_{R}$ decay width, $W_{R}$ masses below 2.35 (1.63) TeV are excluded at a $95\%$ confidence level, assuming the $N_{\tau}$ mass is 0.8 (0.2) times the mass of $W_{R}$ boson. To illustrate the sensitivity of this analysis to other new physics models, focus is also placed on pair production of third-generation scalar leptoquarks with decay into $\tau\tau$bb. 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.