Exploring B_(d,s)-> KK decays through flavour symmetries and QCD-factorisation

We present a new analysis of B_{d,s}->KK modes within the SM, relating them in a controlled way through SU(3)-flavour symmetry and QCD-improved factorisation. We propose a set of sum rules for B_{d,s}-> K^0{\bar K}^0 observables. We determine B_s-> KK branching ratios and CP-asymmetries as functions of A_{dir}(B_d-> K^0{\bar K}^0), pointing out a conflict between BR(B_s-> K+K-) in the SM and data. Finally, we predict the amount of U-spin breaking between B_d-> pi+pi- and B_s-> K+K-.