truecm
It is very important (and helpful!) to keep track of the phase arbitrariness embodied by Eq. (1.6). From the formulae above, one has:
with:
We can use the phase arbitrariness to make one of the quantities in (3.2) and (3.3) to be real. The Wu-Yang convention [8] requires:
The Wu-Yang convention is phenomenologically very useful,
as we shall see presently. It corresponds to shift as much T-violation as
possible away from the dominant, 
, non-leptonic amplitude into
the suppressed, 
one.
In the usual parametrization of the KM matrix precisely the opposite
occurs, namely T-violation appears predominantly in the 
amplitude, due to t-quark exchange in penguin diagrams, while the 
amplitude is predominantly real (except for electroweak penguin effects,
which may become important for large values of the t-quark mass, see
Sect. 5). Of course, amplitudes computed in the latter (KM) convention can
be transformed back to the Wu-Yang phase convention by the transformation
(3.1) with:
We adopt the Wu-Yang convention in the following.