New physics in $B\to K^{\ast }\mu \mu$?

Abstract

Recent experimental results on angular observables in the rare decay $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ show significant deviations from Standard Model predictions. We investigate the possibility that these deviations are due to new physics. Combining all relevant data on $b\to s$ rare decays, we show that a consistent explanation of most anomalies can be obtained by new physics contributing simultaneously to the semi-leptonic vector operator $O_9$ and its chirality-flipped counterpart $O_9^{\prime }$. A partial explanation is possible with new physics in $O_9$ or in dipole operators only. We study in detail the implications for models of new physics, in particular the minimal supersymmetric standard model, models with partial compositeness and generic models with flavour-changing $Z^{\prime }$ bosons. In all considered models, contributions to $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ of the preferred size imply a spectrum close to the TeV scale. We stress that measurements of CP asymmetries in $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ could provide valuable information to narrow down possible new physics explanations.

Comments: 31 pages, 10 figures. v3: Minor clarifications; table with SM predictions and experimental averages added; matches journal version