Photon Distribution Amplitudes in nonlocal chiral quark model

TL;DR

This paper calculates photon distribution amplitudes up to twist four within a nonlocal chiral quark model, incorporating Ward identities and comparing key QCD vacuum parameters with phenomenology.

Contribution

It introduces a method to compute photon distribution amplitudes up to twist four using a nonlocal chiral quark model with a simple pole ansatz, ensuring Ward identity compliance.

Findings

Computed quark condensate and magnetic susceptibility of the QCD vacuum.

Provided analytical expressions for distribution amplitudes and form factors.

Compared vacuum parameters with phenomenological estimates.

Abstract

Photon distribution amplitudes up to twist four are calculated within the nonlocal chiral quark model with a simple pole ansatz for momentum dependence of the constituent quark mass. Calculations are performed using modified electromagnetic vector current in order to satisfy Ward identities. Quark condensate and magnetic susceptibility of the QCD vacuum entering definitions of the distribution amplitudes are computed and compared with existing phenomenological estimates. Both real and off-shell photons are considered and relevant form factors are calculated. Our results are analytical up to the numerical solution of certain algebraic equation.