Mixing-InducedCPAsymmetries in RadiativeBDecays in and beyond the Standard Model

In the standard model (SM) the photon in radiative ${\overline{B}}^0$ and ${\overline{B}}_s$ decays is predominantly left handed. Thus, mixing-induced CP asymmetries in $b\to s\gamma$ and $b\to d\gamma$ are suppressed by $m_s{/m}_b$ and $m_d{/m}_b$, respectively, and are very small. In many extensions of the SM, such as the left-right symmetric model (LRSM), the amplitude of right-handed photons grows proportional to the virtual heavy fermion mass, which can lead to large asymmetries. In the LRSM, asymmetries larger than 50% are possible even when radiative decay rate measurements agree with SM predictions.