Above-Threshold Poles in Model-Independent Form Factor Parametrizations

TL;DR

This paper extends model-independent form factor parametrizations for semileptonic decays to include above-threshold resonant poles, analyzing their impact and interpretation within the analytic structure of Green's functions.

Contribution

It introduces a generalized parametrization method that incorporates above-threshold poles, providing a clearer understanding of their role in form factor modeling.

Findings

Above-threshold poles have minimal effect on form factor parametrizations.

The interpretation of these poles relates to the analytic structure of Green's functions.

Explicit analysis performed for the case of D → π e⁺ νₑ decays.

Abstract

The model-independent parametrization for exclusive hadronic form factors commonly used for semileptonic decays is generalized to allow for the inclusion of above-threshold resonant poles of known mass and width. We discuss the interpretation of such poles, particularly with respect to the analytic structure of the relevant two-point Green's function in which they reside. Their presence has a remarkably small effect on the parametrization, as we show explicitly for the case of $D \to \pi e^+ \nu_e$.