Only the interference of the violating amplitude,
, with the
allowed,
,
amplitude, remains after integrating over the entire three-pion phase space.
The interference of the
allowed,
, with the
violating amplitude,
can be safely
neglected. Similar to the evaluation of
we can write:
Since only the amplitude contributes, and by neglecting
violation in the decay amplitude, we can simply write:
Any violation different from the pure mixing alters only the
imaginary part of
. Such a
violation comes from the
interference of the
decay amplitude with the mixing amplitude.