Search for pair-production of vector-like quarks in final states with at least one $Z$ boson decaying into a pair of electrons or muons in $pp$ collision data collected with the ATLAS detector at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for pair-produced vector-like quarks decaying into a Z boson and a third-generation quark, using ATLAS data at 13 TeV, setting mass limits up to about 1.2 TeV.

Contribution

First search using 13 TeV ATLAS data to set mass limits on vector-like quarks decaying into Z bosons and third-generation quarks.

Findings

No significant excess found over Standard Model predictions.

Excluded vector-like quark masses up to approximately 1.2 TeV.

Set 95% confidence level lower limits on vector-like quark masses.

Abstract

A search for pair-produced vector-like quarks decaying into a $Z$ boson and a third generation quark using 2015 and 2016 $pp$ collision data at $\sqrt{s}~=~13~$TeV collected by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of $36.1~$fb$^{-1}$, is presented. No significant excess over the Standard Model expectation was found so lower exclusion limits at 95% confidence level were set on the vector-like quark masses at 1030 (1210) GeV for singlet (doublet) $T$ and 1010 (1140) GeV for singlet (doublet) $B$.