MEASUREMENT OF R = B(t→Wb)/B(t→Wq) AT DØ.

A measurement of the ratio of branching fractions, R = B(t→Wb)/B(t→Wq), with q being any quark with I3 = -1/2 and Q = -1/3, is presented. This analysis considers samples of single- and double-tagged lepton+jets events obtained with the DØ detector, corresponding to integrated luminosities of 169 pb-1 and 158 pb-1, respectively in the e+jets and μ+jets channels. Two different lifetime taggers, CSIP and SVT, are used. [ABSTRACT FROM AUTHOR]