Search for third-generation scalar leptoquarks decaying to a top quark and a $\tau$ lepton at $\sqrt{s}=$ 13 TeV

TL;DR

This paper reports a search for third-generation scalar leptoquarks decaying into a top quark and a tau lepton using 13 TeV proton-proton collision data, setting new mass exclusion limits up to 900 GeV.

Contribution

It presents the most stringent limits to date on scalar leptoquark production decaying to top quarks and tau leptons, based on CMS data at 13 TeV.

Findings

No evidence for leptoquark pair production was observed.

Masses below 900 GeV are excluded at 95% confidence level.

The analysis improves previous limits on third-generation scalar leptoquarks.

Abstract

A search for pair production of heavy scalar leptoquarks (LQs), each decaying into a top quark and a $\tau$ lepton, is presented. The search considers final states with an electron or a muon, one or two $\tau$ leptons that decayed to hadrons, and additional jets. The data were collected in 2016 in proton-proton collisions at $\sqrt{s}=$ 13 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. No evidence for pair production of LQs is found. Assuming a branching fraction of unity for the decay LQ$ \to $t$\tau$, upper limits on the production cross section are set as a function of LQ mass, excluding masses below 900 GeV at 95% confidence level. These results provide the most stringent limits to date on the production of scalar LQs that decay to a top quark and a $\tau$ lepton.