Importance of Lepton Current in Deeply Virtual Compton Scattering

Chueng-Ryong Ji
North Carolina State University

We discuss the issue of singularity in the lepton current for the 
kinematics of extracting the generalized Parton distribution (GPD) from 
the deeply virtual Compton scattering (DVCS). It reveals an importance of 
the contributions that were often neglected in the reduced calculation 
using the GPD formulation. We present the full calculation of the tree 
level Compton scattering amplitude and discuss what has been missed in the 
reduced calculation of the GPD formulation.