Date of this Version
PHYSICAL REVIEW LETTERS 107, 121802 (2011); DOI: 10.1103/PhysRevLett.107.121802
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 tt̅ final states. The measurement uses data from 5.4 fb-1 of pp̅ collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90±0.04, and we extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element │Vtb│ as │Vtb│= 0.95 ± 0.02, assuming unitarity of the 3X3 CKM matrix.