Dispersive Analysis of $B\to K^{(*)}$ and $B_s\to \phi$ Form Factors

TL;DR

This paper introduces a comprehensive dispersive analysis of $B$ meson decay form factors, incorporating previously neglected branch cuts to reduce systematic uncertainties and providing accessible data for further research.

Contribution

It presents the first simultaneous dispersive analysis of multiple $B$ decay form factors with an improved parametrization that accounts for specific branch cuts, enhancing accuracy.

Findings

Elimination of a major source of systematic uncertainty.

Provision of machine-readable form factor data.

Enhanced understanding of $B$ decay processes.

Abstract

We perform the first simultaneous dispersive analysis of the $B\to K$, $B\to K^*$, and $B_s\to \phi$ form factors. By means of an improved parametrization, we take into account the form factors' below-threshold branch cuts arising from on-shell $\bar{B}_s \pi^0$ and $\bar{B}_s \pi^0 \pi^0$ states, which so far have been ignored in the literature. In this way, we eliminate a source of hard-to-quantify systematic uncertainties. We provide machine-readable files to obtain the full set of the $\bar{B}\to \bar{K}^{(*)}$ and $\bar{B}_s\to \phi$ form factors in and beyond the entire semileptonic phase space.