Single-top-quark production at hadron colliders

Single-top-quark production probes the charged-current weak interaction of the top quark, and provides a direct measurement of the CKM matrix element V_tb. We perform two independent analyses to quantify the accuracy with which the W-gluon fusion (gq⃗tb̅ q) and qq̅ →tb̅ signals can be extracted from the backgrounds at both the Fermilab Tevatron and the CERN LHC. Although perturbation theory breaks down at low transverse momentum for the W-gluon fusion b̅ differential cross section, we show how to obtain a reliable cross section integrated over low b̅ transverse momenta up to a cutoff. We estimate the accuracy with which V_tb can be measured in both analyses, including theoretical and statistical uncertainties. We also show that the polarization of the top quark in W-gluon fusion can be detected at the Fermilab Tevatron and the CERN LHC.