0000000000240061
AUTHOR
I. V. Anikin
Gauge invariance of the deeply virtual Compton scattering amplitude
We analyze in detail the problem of gauge invariance of the deeply virtual Compton scattering (DVCS) amplitude. Using twist-3 one-gluon exchange diagram contributions and the QCD equations of motion, we derive the general gauge invariant expression of the DVCS amplitude on a (pseudo)scalar particle (pion, ${\mathrm{He}}^{4}).$ Similarly to the case of deep inelastic scattering, the amplitude does not depend on the twist-3 quark-gluon correlations at the Born level. The contribution of the derived amplitude to the single-spin asymmetry with longitudinally polarized lepton is calculated.
Single spin asymmetry parameter from deeply virtual compton scattering of hadrons up to twist - three accuracy. 1. Pion case
The study of deeply virtual Compton scattering (DVCS) has shown that electromagnetic gauge invariance requires, to leading order, not only twist-two but additional twist-three contributions. We apply this analysis and, using the Ellis-Furmanski-Petronzio factorization scheme, compute the single- (electron) spin asymmetry arising in the collision of longitudinally polarized electrons with hadrons up to twist-3 accuracy. In order to simplify the kinematics we restrict the actual calculation to pions in the chiral limit. The process is described in terms of the generalized parton distribution functions which we obtain within a bag model framework.