From Diphoton GDAs and Photon GPDs to the chiral odd Photon DA

TL;DR

This paper explores the photon’s unique QCD properties, calculating its anomalous GPDs and DAs, and proposes using transverse spin asymmetry to probe its chiral-odd distribution amplitude.

Contribution

It introduces a method to compute photon anomalous GPDs and DAs, linking perturbative and non-perturbative aspects of the photon’s structure.

Findings

Computed photon anomalous GPDs and DAs.

Proposed using transverse spin asymmetry for probing chiral-odd photon DAs.

Highlighted the dual perturbative and non-perturbative nature of the photon.

Abstract

The photon is a very interesting object for QCD studies since it has both a pointlike coupling to quarks, which yields a perturbative part of photon's wave function, and a non-perturbative coupling related to the magnetic susceptibility of the QCD vacuum and which builds its chiral-odd twist-2 distribution amplitude. The first feature allows us to compute the photon anomalous generalized parton distributions (GPD) and the diphoton generalized distribution amplitudes. The second feature allows us to use a transverse spin asymmetry to probe the chiral odd distribution amplitude of the photon.