Twistthree analysis of photon electroproduction off the pion
Abstract
We study twistthree effects in spin, charge, and azimuthal asymmetries in deeply virtual Compton scattering on a spinzero target. Contributions which are power suppressed in 1/Q generate a new azimuthal angle dependence of the cross section that is not present in the leading twist results. On the other hand, the leading twist terms are not modified by the twistthree contributions. They may get corrected at the twistfour level, however. In the WandzuraWilczek approximation these new terms in the Fourier expansion with respect to the azimuthal angle are entirely determined by the twisttwo generalized parton distributions. We also discuss more general issues such as the general form of the angular dependence of the differential cross section, the validity of factorization at the twistthree level, and the relation of generalized parton distributions to spectral functions.
 Publication:

Physical Review D
 Pub Date:
 December 2001
 DOI:
 10.1103/PhysRevD.64.116002
 arXiv:
 arXiv:hepph/0011314
 Bibcode:
 2001PhRvD..64k6002B
 Keywords:

 11.10.Hi;
 12.38.Bx;
 13.60.Fz;
 Renormalization group evolution of parameters;
 Perturbative calculations;
 Elastic and Compton scattering;
 High Energy Physics  Phenomenology;
 High Energy Physics  Experiment
 EPrint:
 21 pages, LaTeX, 2 figures, text clarifications, an equation, a note and references added