New Physics Search in the Doubly Weak Decay $\overline B^0 \to K^+ \pi^- $

The doubly weak transition $b\to dd{\bar s}$ is highly suppressed in the standard model, which makes it a potential channel to explore new physics signals. We present a study of the exclusive two body wrong sign weak decay $\smash{\overline B}^0\to K^+\pi^-$ belonging to this class within the perturbative QCD approach. We perform a model independent analysis for various effective dimension-6 operators, in which large effects are possible. We further analyze the considered process in example models such as Randall-Sundrum model, including the custodially protected and the bulk-Higgs Randall-Sundrum model. Exploring the experimentally favored parameter spaces of these models leads to a large and significant enhancement of the decay rate, compared to the standard model result, which might be accessible in future experiments. We propose to look for the wrong sign decay $\smash{\overline B}^0\to K^+\pi^-$ via flavour-tagged time-dependent analyses, which can be performed at LHCb and Belle-II.