Testing the Standard Model with Bs-> K^+ K^- Decays
  In the limit of flavor SU(3) symmetry, the amplitudes for Bd->pi^+\pi^- and Bs-> K^+ K^- are related to one another. Taking the values of the weak phases beta and gamma from independent measurements, the ratio Rds=BR(Bs-> K^+K^-)/BR(Bd->pi^+ pi^-) and the two Bd->pi^+pi^- CP asymmetries Adir and Amix depend on only two quantities. By measuring these three observables, one can test for the presence of physics beyond the standard model. In this paper, using present data, and including theoretical uncertainties due to SU(3) breaking, we perform such an analysis. The experimental errors are still very large, but with improved measurements from Babar, Belle and CDF this will be a useful method to search for new physics. 
David London and Joaquim Matias