B_{d,s}^0 --> K^{(*)} K-bar^{(*)}: CP phase alpha and New Physics
  The decays B_{d,s}^0 --> K^{(*)} K-bar^{(*)} can be used to measure the angle alpha of the CKM unitarity triangle. The theoretical error from SU(3) breaking is expected to be small, so that the determination of alpha is clean. Moreover, since B_{d,s}^0 --> K^{(*)} K-bar^{(*)} are pure penguin decays, they are particularly sensitive to the presence of new physics 
Alakabha Datta and David London