omega --> pi0 gamma* and phi --> pi0 gamma* Transition form factors in dispersion theory

TL;DR

This paper computes omega and phi to pi0 gamma* transition form factors using dispersion theory, comparing results with experimental data and advocating for further measurements to explore deviations from vector-meson dominance.

Contribution

It introduces a dispersive approach to calculate transition form factors relying on previous decay analyses and form factors, highlighting deviations from traditional models.

Findings

Agreement with omega --> pi0 mu+ mu- decay spectrum data

Identification of strong deviations from vector-meson dominance

Encouragement for experimental studies of phi --> pi0 l+ l- decays

Abstract

We calculate the omega --> pi0 gamma* and phi --> pi0 gamma* electromagnetic transition form factors based on dispersion theory, relying solely on a previous dispersive analysis of the corresponding three-pion decays and the pion vector form factor. We compare our findings to recent measurements of the omega --> pi0 mu+ mu- decay spectrum by the NA60 collaboration, and strongly encourage experimental investigation of the Okubo-Zweig-Iizuka-forbidden phi --> pi0 l+ l- decays in order to understand the strong deviations from vector-meson dominance found in these transition form factors.