First Measurement of the Ratio B(t-->Wb)/B(t-->Wq) and Associated Limit on the CKM Element Vtb

TL;DR

This paper reports the first measurement of the ratio of top quark decay branching fractions to Wb versus Wq, providing a new limit on the CKM matrix element Vtb based on Tevatron data.

Contribution

It presents the first experimental measurement of the ratio B(t-->Wb)/B(t-->Wq) and sets a new limit on Vtb, confirming standard model predictions.

Findings

Measured ratio R=0.94+/-0.31 (stat+syst)

Established lower limit R>0.61 at 90% C.L.

Provided a limit on Vtb consistent with three-generation unitarity.

Abstract

We present the first measurement of the ratio of branching fraction R= B(t-->wb)/B(t-->Wq) from ppbar collisions at sqrt(s)=1.8 TeV. The data set corresponds to 109 pb-1 of data recorded by the Collider Detector at Fermilab during the 1992-1995 Tevatron run. We measure R=0.94+.31-.24 (stat+syst) or R>0.61 (0.56) at 90 (95) %C.L., in agreement with the standard model predictions. This measurement yields a limit of the Cabibbo-Kobayashi-Maskawa quark mixing matrix element Vtb under the assumption of three generation unitarity.