Extraction of a weak phase from B -> D-(*)pi

To observe CP-violating asymmetries through the interference of a weaker amplitude with a stronger one in B-0 --> D((*))pi and (B) over bar (0) --> D((*))pi decays, one must collect enough events that the intensity associated With the weaker amplitude would be statistically significant. We show that, provided the weaker amplitude is measured separately in B+/- --> D(*)+/- pi(0) decays, the time-integrated approach requires around 2.5 x 10(8) B(B) over bar pairs for measurements of the weak phase sin(2beta+gamma) with an uncertainty of 0.05 or better, We also determine the optimal conditions for precise 2beta+gamma measurements and discuss the possibilities for resolving a discrete ambiguity.