  A measurement of the electroproduction of photons off protons in the deeply
inelastic regime was performed at Jefferson Lab using a nearly 6-GeV electron
beam, a longitudinally polarized proton target and the CEBAF Large Acceptance
Spectrometer. Target-spin asymmetries for $ep\to e'p'\gamma$ events, which
arise from the interference of the deeply virtual Compton scattering and the
Bethe-Heitler processes, were extracted over the widest kinematics in $Q^2$,
$x_B$, $t$ and $\phi$, for 166 four-dimensional bins. In the framework of
Generalized Parton Distributions (GPDs), at leading twist the $t$ dependence of
these asymmetries provides insight on the spatial distribution of the axial
charge of the proton, which appears to be concentrated in its center. These
results also bring important and necessary constraints for the existing
parametrizations of chiral-even GPDs.
