Measurement of B(B-→D0π-) and B(B0→D+π-) and isospin analysis of B¯→Dπ decays

We present new measurements of branching fractions for the color-favored decays B--->D(0)pi(-) and (B) over bar (0)-->D(+)pi(-). Using 9.67x10(6) B (B) over bar pairs collected with the CLEO detector, we obtain the branching fractions B(B--->D(0)pi(-))=(49.7+/-1.2+/-2.9+/-2.2)x10(-4) and B((B) over bar (0)-->D(+)pi(-))=(26.8+/-1.2+/-2.4+/-1.2)x10(-4). The first error is statistical, the second is systematic, and the third is due to the experimental uncertainty on the production ratio of charged and neutral B mesons in Y(4S) decays. These results, together with the current world average for the color-suppressed branching fraction B((B) over bar (0)-->D(0)pi(0)), are used to determine the cosine of the strong phase difference delta(I) between the I=1/2 and I=3/2 isospin amplitudes. We find cos delta(I)=0.863(-0.023-0.035-0.030)(+0.024+0.036+0.038), and obtain a 90% confidence interval of 16.5degrees更多