Single-top-quark production via q qbar -> t bbar

TL;DR

The paper addresses measuring the CKM element $|V_{tb}|$ through single-top production, focusing on the timelike s-channel process $q qbar to t bbar$ as a complementary probe to W-gluon fusion. It provides leading-order cross sections for signal and backgrounds at the Tevatron and LHC, applying detector-level cuts and b-tagging to assess observability. The results indicate that the Tevatron could observe the signal with modest luminosity and extract $|V_{tb}|$ with ~10% precision (improving with more data), while the LHC faces substantial backgrounds that complicate a clean signal. Overall, the study argues for pursuing both channels to map the top-quark charged current across different $q^2$ regimes, leveraging a well-constrained quark-antiquark flux for the $q qbar$ channel.

Abstract

We consider single-top-quark production via the weak process $q\bar q to t\bar b$ at hadron colliders. This process may provide the best measurement of the magnitude of the Cabbibo-Kobayashi-Maskawa matrix element $V_{tb}$. We show that a signal can potentially be observed at the Fermilab Tevatron with 3 $fb^{-1}$ of integrated luminosity. In contrast, the signal is masked at the CERN Large Hadron Collider by top-quark pair production and single-top-quark production via $W$-gluon fusion.