Evidence for production of single top quarks and first direct measurement of |Vtb|

TL;DR

This paper reports the first evidence of single top quark production at the Fermilab Tevatron and provides a direct measurement of the CKM matrix element |Vtb|, using a multivariate analysis on 0.9 fb^-1 data.

Contribution

It presents the first evidence for single top quark production and directly measures |Vtb|, a key parameter in the standard model, from collider data.

Findings

Measured single top production cross section as 4.9 +- 1.4 pb.

Achieved a 3.4 sigma significance for the signal.

Constrained |Vtb| to be between 0.68 and 1 at 95% confidence level.

Abstract

The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron ppbar collider. Using a 0.9 fb^-1 dataset, we apply a multivariate analysis to separate signal from background and measure sigma(ppbar->tb+X,tqb+X) = 4.9 +- 1.4 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the CKM matrix element that describes the Wtb coupling and find 0.68 < |Vtb| <= 1 at 95% C.L. within the standard model.