A determination of the CKM angle α using mixing-induced CP violation in the decays Bd → π+π− and Bd → K0K0

We present a method of determining the CKM angle α by performing simultaneous measurements of the mixing-induced CP asymmetries of the decays Bd → π+π− and Bd → K0K0. The accuracy of our approach is limited by SU(3)-breaking effects originating from b → dss QCD-penguin diagrams. Using plausible power-counting arguments we show that these uncertainties are expected to be of the same order as those arising through electroweak penguins in the standard Gronau-London method in which α is extracted by means of isospin relations among B → ππ decay amplitudes. Therefore our approach, which does not involve the experimentally difficult mode Bd → π0π0 and is essentially unaffected by electroweak penguins, may be an interesting alternative to determine α.