  The recent evidence of large direct CP violation in D0 decay at LHCb suggests
that such CP studies may become an important avenue for understanding CP. In
this paper, we make several suggestions to try to clarify the role of new
physics in these results. We propose that the enhancement needed in the
Standard Model to attribute the observed CP violation in D to two pseudoscalar
modes may not operate for inclusive final states where asymmetries will likely
approximate the quark level expectation. Experimentally testing this principle
requires a search for CP asymmetries in final states containing K and K-bar
with a total energy of less than M_D. We also propose that CP asymmetries may
be enhanced in modes where the tree is color suppressed. In particular, the
final state rho0 rho0 is of special interest; similarly Ds-> rho0 K+ and rho0
K*+ likewise appear interesting. We discuss how isospin symmetry yields
observables sensitive to certain classes of new physics and suppressed in the
Standard Model. Some modes considered in this context are D-> pi pi, rho pi,
rho rho as well as Ds-> K* pi. We also consider how such analysis may
eventually be supplemented by information about the weak phases in D0 decay. In
order to obtain this information experimentally, we consider various methods
for preparing an initial state which is a quantum mechanical mixture of D0 and
D0-bar. This may be done through the use of natural D0 D0-bar oscillations;
observing D0-mesons which arise from Bd or Bs mesons which themselves are
oscillating or from quantum correlations in D0 pairs which arise from either
psi" decay or B-meson decay. Observing CP violation in the magnitudes of decay
amplitudes should be within the capability of experiments in the near future
however obtaining the weak phases through the methods we discuss will likely
require future generations of machines.
