# 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 $\sqrt{s}= 13$ TeV

CMS Collaboration; Canelli, Florencia; Kilminster, Benjamin; Aarestad, Thea; Caminada, Lea; De Cosa, Annapaoloa; Del Burgo, Riccardo; Donato, Silvio; Galloni, Camilla; Hinzmann, Andreas; Hreus, Tomas; Ngadiuba, Jennifer; Pinna, Deborah; Rauco, Giorgia; Robmann, Peter; Salerno, Daniel; Schweiger, Korbinian; Seitz, Claudia; Takahashi, Yuta; Zucchetta, Alberto; et al (2017). 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 $\sqrt{s}= 13$ TeV. Journal of High Energy Physics, 03:077.

## 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-$p_T$ 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 $\sqrt{s}= 13$ 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, $N_ℓ (ℓ = e, μ, τ)$, and right-handed charged bosons, $W_R$, 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 $W_R$ boson and that only the $N_τ$ flavor contributes to the $W_R$ 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.

## 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-$p_T$ 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 $\sqrt{s}= 13$ 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, $N_ℓ (ℓ = e, μ, τ)$, and right-handed charged bosons, $W_R$, 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 $W_R$ boson and that only the $N_τ$ flavor contributes to the $W_R$ 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.

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