ar X iv : h ep - p h / 01 09 10 1 v 1 1 2 Se p 20 01 Non - factorizable effects on B̄

Non-factorizable effects on the color-suppressed B → D(∗)π decay modes are analyzed. Recent observations of B̄0 → D(∗)0π0 by Belle and CLEO strongly suggest that there exists a non-zero strong phase difference between colorallowed and color-suppressed decay modes, and the factorization parameter a2 associated with the color-suppressed decay mode is process dependent. In the heavy quark limit where b and c are heavy, the process dependence of a2(Dπ,D π) is due to the different configuration of the heavy quark spin relative to the light degrees of freedom. From the experimental data, the heavy quark spin symmetry breaking contributions to the non-fatorizable effects are estimated to be 23− 28%. Typeset using REVTEX e-mail: [email protected]