Search for flavor changing neutral currents in decays of top quarks

TL;DR

This paper searches for flavor changing neutral currents in top quark decays using proton-antiproton collision data, setting a new upper limit on the branching ratio of t -> Zq decays.

Contribution

First search for FCNC in top decays at Tevatron, establishing a new upper limit on B(t -> Zq) with 4.1 fb^-1 of data.

Findings

No evidence of FCNC observed.

Set upper limit B(t -> Zq) < 3.2% at 95% CL.

Constraints on anomalous top-Z couplings.

Abstract

We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for ttbar -> l'null + jets (l, l' = e, mu) final states using 4.1 fb^-1 of integrated luminosity of ppbar collisions at sqrt(s) = 1.96 TeV. We extract limits on the branching ratio B(t -> Zq) (q = u, c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B < 3.2% at 95% C.L.