In this section, we study the general process
both within the framework of pure VMD as well as
including chiral loop contributions.
It is
important to have as precise as possible an estimate for
these proceses, because they contribute to the background to
physics reactions like 
or to CP violation
measurements, as it is the case for 
.
We start with the amplitude for the general process within the framework of Vector Meson Dominance (VMD). We find some discrepancies in the literature and update the results.
Subsequently, we look into the possibility that chiral loops may be relevant
to the calculation of these processes, even
at some relatively high energies, like around the 
-mass region. This
attempt to extend ChPT to radiative vector-meson decays,
,
indicates that the effects of (chiral) loops may be
important, at least in some cases [21].
Unambiguous
predictions are then given for 
, 
,
and other processes of interest. The relation
of ChPT amplitudes to the VMD ones is discussed in terms of the
(VM-)resonance saturation of counterterms in the chiral lagrangian.