Time-dependence in B0(t)→π+π− and \ob(t) \to \pi^+ \pi^- is
utilized to obtain a maximal set of information on strong and weak phases. One
can thereby check theoretical predictions of a small strong phase δ
between penguin and tree amplitudes. A discrete ambiguity between δ≃0 and δ≃π may be resolved by comparing the observed
charge-averaged branching ratio predicted for the tree amplitude alone, using
measurements of B→πlν and factorization, or by direct comparison of
parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix with those determined
by other means. It is found that with 150 fb−1 from BaBar and Belle, this
ambiguity will be resolvable if no direct CP violation is found. In the
presence of direct CP violation, the discrete ambiguity between δ and
π−δ becomes less important, vanishing altogether as ∣δ∣→π/2. The role of measurements involving the lifetime difference between
neutral B eigenstates is mentioned briefly.Comment: 14 pages, LaTeX, 5 figures, to be published in Phys. Rev. D. Updated
version with one reference change