Improved measurement of ttZ couplings at the CERN LHC

We consider QCD t (t) over barZ production at the LHC with Z ->nu(nu) over bar and all-hadronic t (t) over bar decays, i.e. pp -> p(T)b (b) over bar +4 jets, as a tool to measure ttZ couplings. This channel has a significantly larger cross section than those where the Z boson decays leptonically. However, t (t) over bar, b (b) over bar +4 jet, t (t) over barj, and t (t) over bar jj production give rise to potentially large backgrounds. We show that these processes can be suppressed to an acceptable level with suitable cuts, and find that adding the p(T)b (b) over bar +4 jet channel to the final states used in previous ttZ couplings analyses will improve the sensitivity by 10%-60%. We also discuss how the measurement of the ttZ couplings may constrain Little Higgs models.