Can there be any new physics in b -> d penguins

We analyze the possibility of observing new physics effects in the $b \to d$ penguin amplitudes. For this purpose, we consider the decay mode $B \to K^0 \bar K^0$, which has only $b \to d$ penguin contributions. Using the QCD factorization approach, we find very tiny CP violating effects in the standard model for this process. Furthermore, we show that the minimal supersymmetric standard model with $LR$ mass insertion and R-parity violating supersymmetric model can provide substantial CP violation effects. Observation of sizable CP violation in this mode would be a clear signal of new physics.