The form factors for the photon to pseudoscalar meson transitions - an update

TL;DR

This paper updates the analysis of photon to pseudoscalar meson transition form factors using a modified perturbative approach that includes quark transverse degrees of freedom, showing good agreement with experimental data.

Contribution

It provides an updated calculation of transition form factors with minimal modifications to meson distribution amplitudes, highlighting the significance of the second Gegenbauer term for the pi-photon form factor.

Findings

Good agreement with experimental data for most form factors

Strong contribution from the second Gegenbauer term in pi-photon form factor

Comments on two virtual photons and time-like region transitions

Abstract

The form factors for the transitions pi-photon, eta-photon, eta'-photon and etac-photon are analyzed within the modified perturbative approach in which quark transverse degrees of freedom are retained. The results for the form factors are compared to experiment in detail. As compared to previous calculations within the same approach only little modifications of the meson distribution amplitudes are required in general in order to achieve agreement with experiment. Only for the pi-photon form factor a strong contribution from the second Gegenbauer term is found. It is also commented on the case of two virtual photons and on the transition form factors in the time-like region.