A simplified approach to determine α and the penguin amplitude in Bd → ππ

The effect of inelastic final-state interactions (IFSIs) on the determination of the weak phase α from the isospin triangles of B → ππ is qualitatively illustrated. Neglecting the electroweak penguins and IFSIs and assuming the dominance of the top-quark loop in strong penguin diagrams, we propose an experimentally accessible way to approximately determine α and the penguin amplitude in Bd → ππ. This approach relies on a simplified isospin consideration and the factorization approximation, and its feasibility is irrelevant to the time-dependent measurements of Bd → ππ.