  A Lattice QCD approach to quark orbital angular momentum in the proton based
on generalized transverse momentum-dependent parton distributions (GTMDs) is
enhanced methodologically by incorporating a direct derivative technique. This
improvement removes a significant numerical bias that had been seen to afflict
results of a previous study. In particular, the value obtained for Ji quark
orbital angular momentum is reconciled with the one obtained independently via
Ji's sum rule, validating the GMTD approach. Since GTMDs simultaneously contain
information about the quark impact parameter and transverse momentum, they
permit a direct evaluation of the cross product of the latter. They are defined
through proton matrix elements of a quark bilocal operator containing a Wilson
line; the choice in Wilson line path allows one to continuously interpolate
from Ji to Jaffe-Manohar quark orbital angular momentum. The latter is seen to
be significantly enhanced in magnitude compared to Ji quark orbital angular
momentum, confirming previous results.
