Remarks on a Technique of Measuring CP phase $\alpha$
  We present a method to measure the CKM phase $\alpha$ and the tree and penguin (strong and electroweak) amplitudes in $B \rightarrow \pi \pi$ 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 $B \rightarrow \pi \pi$. 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. 
N.G. Deshpande, Xiao-Gang He and Sechul Oh