Comment on studying the corrections to factorization in B -> D-(*) X

We propose studying the mechanism of factorization in exclusive decays of t he form B --> D-(*X-) by examining the differential decay rate as a functio n of the invariant mass of the light hadronic state X. If factorization wor ks primarily due to the large N-c limit then its accuracy is not expected t o decrease as the X invariant mass increases. However, if factorization is mostly a consequence of perturbative QCD then the corrections should grow w ith the X invariant mass. Combining data for hadronic tau decays and semile ptonic B decays allows tests of factorization to be made for a variety of f inal states. We discuss the examples of B --> D*pi (+)pi (-)pi (-)pi (0) an d B --> D*omega pi (-). The mode B --> D*omega pi (-) will allow a precisio n study of the dependence of the corrections to factorization on the invari ant mass of the light hadronic state. (C) 2001 Elsevier Science B.V. All ri ghts reserved.