QCD interactions involving a heavy quark with energy much smaller than itsmass can be understood in the context of an effective field theory in which theheavy quark velocity is held fixed while its mass is taken to infinity. Nonleptonicdecays of hadrons containing a heavy quark further simplify when gluonsexchanged carry small momenta compared to the heavy quark mass.
Under these assumptions the ratio of rates for B → D ρ^- and B → D π^- isinvestigated. The reliability of these assumptions is tested by calculating firstorder, one loop QCD corrections, assuming reasonable momentum distributions forthe quarks inside the light mesons.
