MEASURING CP ASYMMETRY IN B-]RHO-PI-DECAYS WITHOUT AMBIGUITIES

We reexamine the question of isospin analysis applied to the rhopi decay modes of the B as a tool to extract the CKM angle between V(ub)*V(ud) and V(tb)*V(td), without ambiguities or uncertainties due to penguin amplitude contributions. We find that a maximum-likelihood fit of the parameters to the full Dalitz plot distribution can successfully extract the parameters-perhaps with as few as 1000 events. This result is from a study of Monte Carlo-generated events without inclusion of detector efficiency or background effects. The interference between channels is a large effect and provides additional constraints on the parameters compared to channel-by-channel studies. These can usually lift the degeneracy between the multiple solutions that plague such studies. The inclusion of charged B decays in the analysis would provide a direct check of the standard model prediction that the penguin amplitude weak phase for this channel is canceled by the weak mixing phase.