Search for flavor changing neutral currents via quark-gluon couplings in single top quark production using 2.3 fb−1 of pp¯ collisions

We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are σtgu<0.20pb and σtgc<0.27pb. These correspond to limits on the top quark decay branching fractions of B(t→gu)<2.0×10−4 and B(t→gc)<3.9×10−3.