Covariant Non-local Chiral Quark Model and Pion-photon Transition Distribution Amplitudes

TL;DR

This paper employs a covariant non-local chiral quark model to compute pion-photon transition distribution amplitudes, revealing non-local effects that align with experimental observations and differ from local models.

Contribution

It introduces a covariant non-local chiral quark model with Ward-Takahashi compliant currents to calculate transition amplitudes, highlighting effects not captured by local models.

Findings

Correct normalization of vector amplitude fixed by axial anomaly

Axial form factor at zero momentum transfer is reduced due to non-locality

Results are consistent with experimental data

Abstract

Using non-local chiral quark model with simple pole ansatz for mass dependence on momentum and non-local currents satisfying Ward-Takahashi identities, we calculate pion to photon transition distribution amplitudes and relevant form factors. For vector amplitude we recover correct normalization fixed by the axial anomaly. We find that due to the non-locality in the vector current, the value of axial form factor at zero momentum transfer is lowered with respect to the vector form factor. Such behaviour - consistent with experiment - is not seen in the local models. Where possible we compare our results to the experimental data.