Transverse Spin / Transverse Momentum Analogy and Gauge Invariance of Deeply Virtual Compton Scattering

Abstract

Using the similarity between twist 3 contributions to transverse spin for usual parton distributions and transverse momentum for non-diagonal parton distributions, we determine for the simple case of a scalar (pion, $H{e}^4$) target the linear in transverse momentum twist-3 contribution to Deeply Virtual Compton amplitude. This allows to write a gauge invariant amplitude for this non-forward process.

LaTeX, 4 pages; Talk at XIII International Symposium on High Energy Spin Physics (Protvino, September 8-12 1998)