Deeply Virtual Compton Scattering (DVCS), where a high energy electron
scatters off an individual parton in a nucleon which emits a high-energy
photon as a result, is the simplest process to access Generalized Parton
Distributions (GPDs) of the nucleon. The DVCS process interferes at the
amplitude level with the Bethe-Heitler (BH) process, where the real
photon is emitted either by the incoming or the scattered electron. The
resulting DVCS-BH interference terms are connected to linear
combinations of GPDs and are accessible through polarization observables
including spin asymmetry measurements. The sensitivity to the four
leading-order twist-2 GPDs depends on the polarization
observable extracted, making different polarization observable
measurements complementary in the effort of GPD extraction.
This talk focuses on the work and results obtained at Jefferson Lab
using a 6 GeV polarized electron beam, longitudinally polarized (via
Dynamic Nuclear Polarization) proton target and the CEBAF Large
Acceptance Spectrometer equipped with an additional inner calorimeter
for enhanced low angle photon coverage. The high statistics collected
allow for detailed studies of the Q2, xB and t dependencies of 3
spin-asymmetries (beam-spin, target-spin, and double-spin) over a wide
range of kinematics. Preliminary results for the 3 spin-asymmetries will
be shown.
University of Connecticut at Storrs and Jefferson Laboratory