Search for vector-like quarks in events with two oppositely charged leptons and jets in proton–proton collisions at $$\sqrt{s} = 13\,\text {Te}\text {V} $$ s = 13 Te

Abstract

Abstract A search for the pair production of heavy vector-like partners

$$\mathrm {T}$$

T

and

$$\mathrm {B}$$

B

of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using proton–proton collisions at

$$\sqrt{s} = 13\,\text {Te}\text {V} $$

s

= 13

Te

. The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9

$$\,\text {fb}^{-1}$$

fb

- 1

. Final states studied for

$$\mathrm {T} \overline{\mathrm {T}} $$

T

T ¯

production include those where one of the

$$\mathrm {T}$$

T

quarks decays via

$$\mathrm {T} \rightarrow \mathrm {t}\mathrm {Z}$$

T → t Z

and the other via

$$\mathrm {T} \rightarrow \mathrm {b}\mathrm {W}$$

T → b W

,

$$\mathrm {t}\mathrm {Z}$$

t Z

, or

$$\mathrm {t}\mathrm {H} $$

t H

, where

$$\mathrm {H}$$

H

is a Higgs boson. For the

$$\mathrm {B} \overline{\mathrm {B}} $$

B

B ¯

case, final states include those where one of the

$$\mathrm {B}$$

B

quarks decays via

$$\mathrm {B} \rightarrow \mathrm {b}\mathrm {Z}$$

B → b Z

and the other

$$\mathrm {B} \rightarrow \mathrm {t}\mathrm {W}$$

B → t W

,

$$\mathrm {b}\mathrm {Z}$$

b Z

, or

$$\mathrm {b}\mathrm {H} $$

b H

. Events with two oppositely charged electrons or muons, consistent with coming from the decay of a

$$\mathrm {Z}$$

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

$$\mathrm {T}$$

T

and

$$\mathrm {B}$$

B

quarks for a range of branching fractions. Assuming 100% branching fractions for

$$\mathrm {T} \rightarrow \mathrm {t}\mathrm {Z}$$

T → t Z

, and

$$\mathrm {B} \rightarrow \mathrm {b}\mathrm {Z}$$

B → b Z

,

$$\mathrm {T}$$

T

and

$$\mathrm {B}$$

B

quark mass values below 1280 and 1130

$$\,\text {Ge}\text {V}$$

Ge

, respectively, are excluded.