Strong interaction effects are addressed in connection to extracting |V_{ cb}|. A comprehensive approach is described not relying on a 1/m_c expansion; it allows a percent accuracy without ad hoc assumptions about higher-order effects. An alternative to the M_X^2 variable is proposed improving convergence. Intrinsic hardness of integrated observables with a cut on E_\ell is discussed; it can be responsible for the behavior of <M_X^2> reported by BaBar. Consequences of the proximity to the `BPS' limit are considered.
Categories: hep-ph