Angular analysis of $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$

TL;DR

This paper measures angular observables in the decay of B0 mesons to K*0 and lepton pairs, providing data that tests Standard Model predictions and investigates the P5' anomaly reported by LHCb.

Contribution

First measurement of four angular observables in B0 to K*0 lepton decays using Belle data, testing Standard Model predictions and anomalies.

Findings

Results are consistent with Standard Model predictions.

Data provides insight into the P5' anomaly.

Analysis covers five q^2 bins.

Abstract

We present a measurement of angular observables, $P_4'$, $P_5'$, $P_6'$, $P_8'$, in the decay $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$, where $\ell^+\ell^-$ is either $e^+e^-$ or $\mu^+\mu^-$. 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. Four angular observables, $P_{4,5,6,8}'$ are extracted in five bins of the invariant mass squared of the lepton system, $q^2$. We compare our results for $P_{4,5,6,8}'$ with Standard Model predictions including the $q^2$ region in which the LHCb collaboration reported the so-called $P_5'$ anomaly.