  We study leptonic CP and flavor violations in supersymmetric (SUSY) grand
unified theory (GUT) with right handed neutrinos, paying attention to the
renormalization group effects on the slepton mass matrices due to the neutrino
and GUT Yukawa interactions. In particular, we study in detail the impacts of
the so-called Casas- Ibarra parameters on CP and flavor violating observables.
The renormalization group effects induce CP and flavor violating elements of
the SUSY breaking scalar mass squared matrices, which may result in sizable
leptonic CP and flavor violating signals. Assuming seesaw formula for the
active neutrino masses, the renormalization group effects have been often
thought to be negligible as the right-handed neutrino masses become small. With
the most general form of the neutrino Yukawa matrix, i.e., taking into account
the Casas-Ibarra parameters, however, this is not the case. We found that the
maximal possible sizes of signals of leptonic CP and flavor violating processes
are found to be insensitive to the mass scale of the right-handed neutrinos and
that they are as large as (or larger than) the present experimental bounds
irrespective of the right-handed neutrino masses.
