Azimuthal Angle Distribution in $B \to K^* (\to K \pi) \ell^+ \ell^- $ at low invariant $m_{\ell^+ \ell^-}$ Region

Abstract

We present the angular distribution of the rare B decay, $B \to K^* (\to K \pi) \ell^+ \ell^-$. By studying the azimuthal angle distribution in the low invariant mass region of dileptons, we can probe new physics effects efficiently. In particular, this distribution is found to be quite sensitive to the ratio of the contributions from two independent magnetic moment operators, which also contribute to $B \to K^* \gamma$. Therefore, our method can be very useful when new physics is introduced without changing the total decay rate of the $b \to s \gamma$. The angular distributions are compared with the predictions of the standard model, and are shown for the cases when the afore-mentioned ratio is different from the standard model prediction.