Long-distance effects in $B\to K^*\ell\ell$ from Analyticity

TL;DR

This paper introduces a new systematic method to accurately determine long-distance effects in B to K* l+l- decays below the charm threshold, improving Standard Model predictions and enabling precise New Physics analyses.

Contribution

A novel, systematic approach to quantify long-distance contributions in B to K* l+l- decays, applicable across various decay modes and kinematic regions.

Findings

Most consistent determination of long-distance effects to date.

Enables reliable Standard Model predictions for key observables.

Facilitates precise New Physics fits to Wilson coefficients.

Abstract

We discuss a novel approach to systematically determine the long-distance contribution to $B\to K^*\ell\ell$ decays in the kinematic region where the dilepton invariant mass is below the open charm threshold. This approach provides the most consistent and reliable determination to date and can be used to compute Standard Model predictions for all observables of interest, including the kinematic region where the dilepton invariant mass lies between the $J/\psi$ and the $\psi(2S)$ resonances. We illustrate the power of our results by performing a New Physics fit to the Wilson coefficient $C_9$. This approach is systematically improvable from theoretical and experimental sides, and applies to other decay modes of the type $B\to V\ell\ell$, $B\to P\ell\ell$ and $B\to V\gamma$.