Single top production in association with a Z boson at the LHC

Abstract

We present results for the production of a Z boson in association with single top at next-to-leading order (NLO), including the decay of the top quark and the Z boson. This electroweak process gives rise to the trilepton signature l+l-l'+- + jets + missing energy. We present results for this signature and show that the rate is competitive with the contribution of the mixed strong and electroweak production process, ttZ. As such it should be observable in the full data sample from LHC running at $\sqrt{s}=8$ TeV. The single top + Z process is a hitherto unconsidered irreducible background in searches for flavour changing neutral current decays of the top quark in tt production. For a selection of cuts used at the LHC involving a b-tag it is the dominant background. In an appendix we also briefly discuss the impact of NLO corrections on the related tH process.