A Model for the Off-forward Structure Functions of the Pion
arXiv:hep-ph/0310184 · doi:10.1016/j.physletb.2004.03.023
Abstract
We extend our model for the pion, which we used previously to calculate its diagonal structure function, to the off-forward case. The imaginary part of the off-forward gamma* pi -> gamma* pi scattering amplitude is evaluated in the chiral limit (m_pi=0) and related to the twist-two and twist-three generalised parton distributions, H, H3, H3tilde. Non-perturbative effects, linked to the size of the pion and still preserving gauge invariance, are included. Remarkable new relations between H, H3 and H3tilde are obtained and discussed.
9 pages, 20 figures, LaTeX, uses ulg_ptf.cls (included); v2: Form factors dropped in favour of GPD's, comparison between Wandzura-Wilczek approximation and our relations added