$B \to K^* \ell \ell$ Standard Model contributions -- Zooming in on high $q^2$

TL;DR

This paper assesses the accuracy of the operator product expansion in describing $B o K^* o K \, \pi \ell \ell$ decays at high $q^2$, emphasizing the importance of binning strategies for precision in flavor physics.

Contribution

It introduces a data-driven method to evaluate the OPE's validity in $B o K^* \ell \ell$ decays, highlighting the effectiveness of near-endpoint bins for precision.

Findings

OPE describes high-$q^2$ bins near the kinematic endpoint well.

Finer binning improves control over theoretical uncertainties.

Near-endpoint bins are optimal for precision studies.

Abstract

To further precision studies with $B \to K^{(*)} \ell \ell$ decays in the high-$q^2$ window uncertainties related to the operator product expansion (OPE) need to be scrutinized. How well can the OPE describe $B \to K^* (\to K \pi) \ell \ell$ angular distributions for a given binning in view of the local charm resonance structure? We present a data-driven method to access this quantitatively. Our analysis suggests that the bins which are near the kinematic endpoint are best described by the OPE and should be pursued for precision studies. At the same time measurements with finer binning help controlling the uncertainties.