Photon distribution amplitudes and light-cone wave functions in chiral quark models

Abstract

The leading- and higher-twist distribution amplitudes and light-cone wave functions of real and virtual photons are analyzed in chiral quark models. The calculations are performed in the nonlocal quark model based on the instanton picture of QCD vacuum, as well as in the spectral quark model and the Nambu--Jona-Lasinio model with the Pauli-Villars regulator, which both treat interaction of quarks with external fields locally. We find that in all considered models the leading-twist distribution amplitudes of the real photon defined at the quark-model momentum scale are constant or remarkably close to the constant in the $x$ variable, thus are far from the asymptotic limit form. The QCD evolution to higher momentum scales is necessary and we carry it out at the leading order of the perturbative theory for the leading-twist amplitudes. We provide estimates for the magnetic susceptibility of the quark condensate ${\chi }_m$ and the coupling $f_{3\gamma }$, which in the nonlocal model turn out to be close to the estimates from QCD sum rules. We find the higher-twist distribution amplitudes at the quark model scale and compare them to the Wandzura-Wilczek estimates. In addition, in the spectral model we evaluate the distribution amplitudes and light-cone wave functions of the $\rho$-meson.

24 pages, 15 figures

References in corpus (2)

• Magnetic susceptibility of the QCD vacuum
• Pion transition form factor and distribution amplitudes in large-Nc Regge models

Cited by in corpus (8)

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• Covariant Non-local Chiral Quark Model and Pion-photon Transition Distribution Amplitudes
• Confined Chiral Solitons in the Spectral Quark Model
• Light-cone sum rules for the $N\gamma \Delta$ transitions for real photons
• DVCS via color dipoles: Nonperturbative effects
• Real Compton Scattering via Color Dipoles
• Photon interactions and chiral dynamics