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

TL;DR

This paper searches for flavor changing neutral currents involving quark-gluon couplings in single top quark production, setting limits on these rare processes using data from the Fermilab Tevatron Collider.

Contribution

It introduces a novel analysis using Bayesian neural networks to distinguish signal from background in single top events, setting new limits on top quark FCNC couplings.

Findings

No significant excess observed over background expectations.

Set upper limits on FCNC cross sections: sigma_tgu<0.20pb, sigma_tgc<0.27pb.

Limits on top quark decay branching fractions: B(t->gu)<2.0×10^-4, B(t->gc)<3.9×10^-3.

Abstract

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 sigma_tgu<0.20pb and sigma_tgc<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.