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

TL;DR

This study measures angular observables and tests lepton flavor universality in B to K* l+ l- decays using Belle data, finding results mostly consistent with the Standard Model but with a notable 2.6 sigma deviation in muon modes.

Contribution

First measurement of angular observables and lepton flavor universality test in B to K* l+ l- decays with Belle data, providing new insights into potential deviations from the Standard Model.

Findings

Results are consistent with Standard Model expectations.

Largest deviation observed in muon modes with 2.6 sigma significance.

No definitive evidence of lepton flavor universality violation.

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 $2.6\sigma$.