Electroweak penguins in isospin-violating Bs decays

The 2. 5 sigma discrepancy between theory and experiment observed in the difference Delta A(CP) = A(CP)(B- -> pi(0) K-) - ACP((B) over bar (0) -> pi K-+(-)) can be explained by a new electroweak (EW) penguin amplitude. Motivated by this result, we have analyzed the purely isospin-violating decays (B) over bar (s) -> phi pi(0) and (B) over bar (s) -> phi rho(0), which are dominated by EW penguins. Our results extend the analysis in [1] and have recently been published in [2]. Here we give a brief overview of the outcome. We show that in presence of a new EW penguin amplitude the two B-s branching ratios can be enhanced by an order of magnitude without violating any constraints from other hadronic B decays. This makes them very interesting modes for LHCb and Super B factories. We perform both a model-independent analysis and a study within realistic New Physics (NP) models such as a modified-Z(0)-penguin scenario, a model with an additional Z' boson and the MSSM, including a fit to B -> pi K data and the relevant experimental constraints throughout. In the model-independent case we study effective b -> s (q) over barq couplings and distinguish between several possible chirality structures. Constraints arise from a large number of hadronic B decays such as B -> pi K-(*()), rho K-(*()), phi K-(*()) etc. The preferred fit regions are rather large and allow for order-of-magnitude enhancements (see plots). In concrete models the new amplitude can often be correlated with other flavour phenomena, such as semileptonic B decays and B-s-(B) over bar (s) mixing, which set stringent constraints on the enhancement of the two B-s decays. In particular we find that, contrary to claims in the literature, EW penguins in the MSSM can reduce the discrepancy in Delta A(CP) only marginally. Consequently no visible enhancement of (B) over bar (s) -> phi pi(0), phi rho(0) is expected for this model. As byproducts of our work we update the Standard Model (SM) predictions to BR((B) over bar (s) -> phi pi(0)) = 1.6(0.3)(+)(1.1).10(-7) and BR((B) over bar (s) -> phi rho(0)) = 4.4(0.7)(+)(2.7).10(-7) and performa state-of-the-art analysis of B -> pi K amplitudes in QCD factorisation (QCDF).