Z -peaked excess from heavy gluon decays to vectorlike quarks

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/Randall-Sundrum theories. We find that composite Higgs theories with custodial symmetry protection to the Zbb¯ coupling predict a significant contribution to ZZbb (and to hhbb) final states coming from heavy gluon decays to pairs of bottom partner vectorlike quarks. The heavy gluon to vectorlike quark signal is largely accepted by the ATLAS selection if one of the Z bosons in the ZZbb final state decays leptonically and the other to neutrinos. For a bottom partner of ∼900GeV, 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 ∼(0.3-0.65)gS. We briefly discuss the implication of this result for future experimental tests.