Lepton-Flavor-Dependent Angular Analysis of $B\to K^\ast \ell^+\ell^-$

Abstract

We present a measurement of angular observables and a test of lepton flavor universality in the $B\to K^\ast \ell^+\ell^-$ decay, where $\ell$ is either $e$ or $\mu$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711~\mathrm{fb}^{-1}$ containing $772\times 10^{6}$ $B\bar B$ pairs, collected at the $\Upsilon(4S)$ resonance with the Belle detector at the asymmetric-energy $e^+e^-$ collider KEKB. The result is consistent with Standard Model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of $2.6\sigma$.