9 Symmetry Violations and Quark Flavour Physics
577
Fig. 9.22 Result of the fit to the Wu–Yang triangle relations between η +− , η 00 , ε and ε . (a)
Correlation of e ε and m ε ; (b) correlation of e(ε /ε) and m(ε /ε). The boundaries of the
black areas correspond to one-standard-deviation uncertainties
The result of this fit is, with χ 2 /ndf = 3/4
ε
ε
= (−3.2 ± 4.4) × 10
−5
(9.176)
and
m ε = (1.530 ± 0.005) × 10
−3 .
(9.177)
Also, the real part of ε is constrained by the fit:
e ε = (1.619 ± 0.005) × 10
−3
The result of this fit is expressed in correlation plots for e ε and m ε, and for
e(ε /ε) and m(ε /ε), in Fig. 9.22.
The result for direct CP violation (9.175) can also be quoted as a decay
asymmetry between the K 0 and K 0 decay rates to a π + π − final state. If the
amplitudes are called a = amp(K 0 → π + π − ) and a = amp(K 0 → π + π − ),
then this asymmetry is
A =
Γ (K 0 → π + π − ) − Γ (K 0 → π + π − )
Γ (K 0 → π + π − ) + Γ (K 0 → π + π − )
=
|a| 2 − |a| 2
|a| 2 + |a| 2 .
(9.178)