Z-peaked excess from heavy gluon decays to vector-like quarks

TL;DR

This paper proposes that a recent ATLAS excess in Z-peaked dilepton events can be explained by heavy gluon decays into vector-like quarks within composite Higgs models, predicting specific mass ranges and decay signatures.

Contribution

It introduces a novel interpretation of the ATLAS excess as a heavy gluon to vector-like quark decay signal in composite Higgs theories with custodial symmetry.

Findings

ATLAS excess can be explained by heavy gluon decays to bottom-partner quarks.

Heavy gluon masses around 1.87-2.15 TeV fit the observed excess.

Model predicts specific decay channels and parameter space for future tests.

Abstract

A 3 sigma excess has been recently announced by ATLAS in events with Z-peaked dilepton pairs, jets, and large transverse missing energy. We interpret this finding in the context of composite Higgs / RS theories. We find that composite Higgs theories with custodial symmetry protection to the $Zb\bar{b}$ coupling predict a significant contribution to $ZZbb$ (and to $hhbb$) final states coming from heavy gluon decays to pairs of bottom-partner vector-like quarks. The heavy gluon to vector-like quarks signal is largely accepted by the ATLAS selection if one of the $Z$ boson in the $ZZbb$ final state decays leptonically and the other to neutrinos. For a bottom partner of $\sim$900 GeV, we find that the ATLAS excess can be reproduced by composite Higgs models, in an experimentally allowed parameter space, for heavy gluon masses roughly in a range 1.87 - 2.15 TeV and for heavy gluon couplings to light quarks within $\sim(0.3-0.65) g_S$. We briefly discuss the implication of this result for future experimental tests.