Measurement of the Differential Branching Fraction and Forward-Backward Asymmetry for B->K(*)l+l-

TL;DR

This study measures various decay properties of B->K(*)l+l- processes using a large data sample, providing insights into their differential branching fractions, asymmetries, and polarization, with some results deviating from Standard Model predictions.

Contribution

The paper presents the first detailed measurements of multiple decay observables for B->K(*)l+l- using 657 million BB pairs, including differential branching fractions and asymmetries, highlighting potential deviations from the Standard Model.

Findings

Fitted A_FB spectrum is shifted positively from SM expectations.

Measured branching fractions are consistent with previous results within uncertainties.

Lepton flavor ratios are close to unity, supporting lepton universality.

Abstract

We study B->K(*)l+l- decays based on a large data sample of 657 million BB pairs collected with the Belle detector at the KEKB e+e- collider. The differential branching fraction, the isospin asymmetry, the K* polarization, and the forward-backward asymmetry (A_FB) as functions of q^2 are reported. The fitted A_FB spectrum tends to be shifted toward the positive side from the SM expectation. The measured branching fractions and lepton flavor ratios (electron/muon) are B(B->K*l+l-)=(10.8+1.1-1.0+-0.9)*10^-7, B(B->Kl+l-)=(4.8+0.5-0.4+-0.3)*10^-7, R_K*=1.21+-0.25+-0.08, and R_K=0.97+-0.18+-0.06, respectively.