Determining the Factorization Parameter and Strong Phase Differences in B-->D^(*)\pi Decays

The first observation of the color-suppressed decay mode \bar{B}^0_d --> D^()0 \pi^0 by the Belle and CLEO Collaborations makes a quantitative analysis of the isospin relations for the amplitudes of B --> D^()\pi possible. The strong (isospin) phase difference in B --> D\pi transitions is found to be about 29^\circ by use the Belle data or 26^\circ by use of the CLEO data, implying that final-state interactions might not be negligible. Applying the factorization approximation to I=3/2 and I=1/2 isospin amplitudes of B --> D\pi decays, we obtain the ratio of the effective Wilson coefficients a^{eff}_1 and a^{eff}_2: a^{eff}_2/a^{eff}_1 \approx 0.27. A similar analysis shows that the magnitude of final-state interactions in B --> D^*\pi might be comparable with that in B --> D\pi, and the factorization hypothesis works consistently in both of them.