# Search for vector-like quarks in events with two oppositely charged leptons and jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV

## TL;DR

This paper reports a search for heavy vector-like quarks T and B in proton-proton collisions at 13 TeV, setting mass exclusion limits based on observed event data consistent with standard model backgrounds.

## Contribution

The study provides the first mass exclusion limits for vector-like T and B quarks at 13 TeV using CMS data, considering multiple decay channels and branching fractions.

## Key findings

- Excluded T quark masses below 1280 GeV for 100% T→ tZ decay
- Excluded B quark masses below 1130 GeV for 100% B→ bZ decay
- Observed event counts are consistent with standard model predictions.

## Abstract

A search for the pair production of heavy vector-like partners T and B of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using proton-proton collisions at $\sqrt{s} =$ 13 TeV. The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. Final states studied for $\mathrm{T\overline{T}}$ production include those where one of the T quarks decays via T $\to$ tZ and the other via T $\to$ bW, tZ, or tH, where H is a Higgs boson. For the $\mathrm{B\overline{B}}$ case, final states include those where one of the B quarks decays via B $\to$ bZ and the other B $\to$ tW, bZ, or bH. Events with two oppositely charged electrons or muons, consistent with coming from the decay of a Z boson, and jets are investigated. The number of observed events is consistent with standard model background estimations. Lower limits at 95% confidence level are placed on the masses of the T and B quarks for a range of branching fractions. Assuming 100% branching fractions for T $\to$ tZ, and B $\to$ bZ, T and B quark mass values below 1280 and 1130 GeV, respectively, are excluded.