Precision measurement of the ratio B(t -> Wb)/B(t -> Wq)

TL;DR

This paper reports a precise measurement of the ratio of top quark decays to Wb versus all Wq decays, using Tevatron data, and derives the CKM matrix element |Vtb| from this ratio.

Contribution

The paper provides the first precise measurement of the ratio B(t -> Wb)/B(t -> Wq) and extracts |Vtb| assuming CKM unitarity, improving understanding of top quark decays.

Findings

Measured R = 0.90 +/- 0.04

Extracted |Vtb| = 0.95 +/- 0.02

Supports the Standard Model predictions

Abstract

We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s or b quark, in the lepton+jets and dilepton ttbar final states. The measurement uses data from 5.4 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the CKM matrix element |Vtb| as |Vtb| = 0.95 +/- 0.02, assuming unitarity of the 3x3 CKM matrix.