Testing factorization in B→D(*) X decays

In QCD the amplitude for B̄⁰→D(*)⁺ π^- factorizes in the large N_c limit or in the large energy limit Q ≫Λ_QCD where Q = {m_b, m _c, m_b-m_c}. Data also suggest factorization in the exclusive processes B →D*π⁺ π^- π^- π⁰ and B→D*ωπ^-; however, by themselves neither a large N_c nor a large Q can account for this. We give exact large N_c relations among isospin amplitudes for B̄→D(*)X and B̄→D(*)X, which can be used to test factorization through exclusive or inclusive measurements. Noting that the condition for large energy release in B̄⁰→D⁺ π^- is enforced by the small velocity limit, m_b≫ m_b-m_c≫Λ, we propose that the combined large N_c and SV limits justify factorization in B→D(*)X. This combined limit is tested with the B→D*X inclusive decay spectrum measured by CLEO.