Search for single production of a vector-like quark via a heavy gluon in the $4b$ final state with the ATLAS detector in $pp$ collisions at $\sqrt{s} = 8$ TeV

TL;DR

This paper searches for a heavy gluon decaying into vector-like quarks resulting in a four b-quark final state, setting new limits on the masses of these particles based on ATLAS data at 8 TeV.

Contribution

It introduces a novel search for heavy gluons decaying into vector-like quarks in a four b-jet final state using ATLAS data, providing new mass exclusion limits.

Findings

No significant excess observed over Standard Model predictions.

Set upper limits on production cross section times branching ratio.

Established lower mass bounds on heavy gluon and vector-like quark masses.

Abstract

A search is performed for the process $pp \to G^* \to B_H\bar b/\bar B_H b \to H b \bar b \to b\bar bb\bar b$, predicted in composite Higgs scenarios, where $G^*$ is a heavy colour octet vector resonance and $B_H$ a vector-like quark of charge $-1/3$. The data were obtained from $pp$ collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.5 fb$^{-1}$, recorded by the ATLAS detector at the LHC. The largest background, multijet production, is estimated using a data-driven method. No significant excess of events with respect to Standard Model predictions is observed, and upper limits on the production cross section times branching ratio are set. Comparisons to the predictions from a specific benchmark model are made, resulting in lower mass limits in the two-dimensional mass plane of $m_{G^*}$ vs. $m_{B_H}$.