Eur. Phys. J. C (2014) 74: 2787
https://doi.org/10.1140/epjc/s10052-014-2787-5

Regular Article - Theoretical Physics

Off-shell photon distribution amplitudes in the low-energy effective theory of QCD

Department of Physics, School of Physics Science and Technology, Wuhan University, Wuhan, 430072, China

^* e-mail: jpliu@whu.edu.cn

Received: 20 November 2013
Accepted: 18 February 2014
Published online: 4 March 2014

Abstract

Based on the principle of Lorentz covariance the transition matrix elements from an off-shell photon state to the vacuum are decomposed into the light-cone photon distribution amplitudes (DAs), in which only two transversal DAs survive in the on-shell limit. The eight off-shell light-cone photon DAs corresponding to chiral odd and chiral even up to twist four, and the corresponding coupling constants are studied systematically in the instanton vacuum model of quantum chromodynamics (QCD). The various individual photon DAs multiplied by their corresponding coupling constants are expressed in terms of the correlation functions, which are connected with the spectral densities of an effective quark propagator and then evaluated in the low-energy effective theory derived from the instanton vacuum model of QCD. The explicit analytical expressions and the numerical results for the photon DAs and their coupling constants are given.