Search for production of single top quarks via $tcg$ and $tug$ flavor-changing neutral current couplings

TL;DR

This study searches for single top quark production via flavor-changing neutral current couplings involving gluons and charm or up quarks, using Tevatron data, and sets upper limits on the anomalous couplings.

Contribution

First search for single top production via $tcg$ and $tug$ FCNC couplings at Tevatron, establishing new upper limits on these anomalous couplings.

Findings

No significant deviation from standard model predictions.

Upper limits on $ ilde{ m ext{kappa}}_{c} ext{Lambda}$ and $ ilde{ m ext{kappa}}_{u} ext{Lambda}$.

Constraints improve previous bounds on FCNC top couplings.

Abstract

We search for the production of single top quarks via flavor-changing neutral current couplings of a gluon to the top quark and a charm ($c$) or up ($u$) quark. We analyze 230 pb$^{-1}$ of lepton + jets data from $\ppbar$ collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters $\kappacLambda$ and $\kappauLambda$, where $\kappag$ define the strength of $tcg$ and $tug$ couplings, and $\Lambda$ defines the scale of new physics. The limits at 95% C.L. are: $\kappacLambda < 0.15 \rm TeV^{-1}$ and $\kappauLambda < 0.037 \rm TeV^{-1}$.