Remarks on a technique of measuring CP phase α

We present a method to measure the CKM phase α and the tree and penguin (strong and electroweak) amplitudes in B → ππ decays, based on isospin consideration and the weak assumption that all tree amplitudes have a common strong phase and all penguin amplitudes have a different common phase. The method needs only the time-independent measurements of the relevant decay rates in B → ππ. We also propose a method to experimentally examine the validity of the assumption that all penguin amplitudes have the same strong phases, and to extract detailed informations about the hadronic matrix elements.