9 Symmetry Violations and Quark Flavour Physics
561
and π 0 π 0 decays behind a regenerator in the kTeV experiment [180] (Sect. 9.5.5.2).
Here, the uncertainty arising from the phase of coherent regeneration (which is the
determining uncertainty in the Φ +− measurement) cancels in the comparison of the
two decay modes. The authors of [180] conclude that
Φ 00 − Φ +− = (0.39 ± 0.50)
◦ .
(9.142)
Together with an earlier measurement by E731/E773 [179] and the NA31 measurement (9.140), this gives
Φ 00 − Φ +− = (0.36 ± 0.43)
◦ .
(9.143)
9.5.5.5 Measurement of +− from a Tagged Pure Strangeness State
The CPLEAR experiment (Sect. 9.5.4.7) offers the unique feature of tagging a
pure neutral strangeness state K 0 or K 0 produced in a pp annihilation at rest
by identifying a charged kaon produced in the same reaction. Compared with
the vacuum interference experiments (Sect. 9.5.5.3), this offers the advantage of
a full-size interference term, whereas in the vacuum interference experiments, an
incoherent mixture of (predominantly) K 0 and K 0 forms the initial state, and the
interference term is diluted.
The interference term is visualized by measuring the decay-rate asymmetry for
decays into π + π − ,
A +− (τ ) =
N(τ ) − N(τ )
N(τ ) + N(τ )
(9.144)
= 2 e ε − 2 |η +− |e
−(1/2)Γ S τ cos((m τ − Φ +− ) .
(9.145)
In the corresponding experimental distribution, the background was subtracted
and the events were appropriately weighted taking into account the tagging efficiencies for K 0 and K 0 . The result is shown in Fig. 9.13 [181]. The result of a fit to these
data gives values for Φ +− and |η +− |, which are correlated with the values chosen
for m and τ S , respectively.
The correlation parameters are
δΦ +− = 0.30((m − 0.5301 × 10
10 s
−1 )
(9.146)
and
δ|η +− | = 0.09(τ S − 0.8934 × 10
−10 s) .
(9.147)
561
and π 0 π 0 decays behind a regenerator in the kTeV experiment [180] (Sect. 9.5.5.2).
Here, the uncertainty arising from the phase of coherent regeneration (which is the
determining uncertainty in the Φ +− measurement) cancels in the comparison of the
two decay modes. The authors of [180] conclude that
Φ 00 − Φ +− = (0.39 ± 0.50)
◦ .
(9.142)
Together with an earlier measurement by E731/E773 [179] and the NA31 measurement (9.140), this gives
Φ 00 − Φ +− = (0.36 ± 0.43)
◦ .
(9.143)
9.5.5.5 Measurement of +− from a Tagged Pure Strangeness State
The CPLEAR experiment (Sect. 9.5.4.7) offers the unique feature of tagging a
pure neutral strangeness state K 0 or K 0 produced in a pp annihilation at rest
by identifying a charged kaon produced in the same reaction. Compared with
the vacuum interference experiments (Sect. 9.5.5.3), this offers the advantage of
a full-size interference term, whereas in the vacuum interference experiments, an
incoherent mixture of (predominantly) K 0 and K 0 forms the initial state, and the
interference term is diluted.
The interference term is visualized by measuring the decay-rate asymmetry for
decays into π + π − ,
A +− (τ ) =
N(τ ) − N(τ )
N(τ ) + N(τ )
(9.144)
= 2 e ε − 2 |η +− |e
−(1/2)Γ S τ cos((m τ − Φ +− ) .
(9.145)
In the corresponding experimental distribution, the background was subtracted
and the events were appropriately weighted taking into account the tagging efficiencies for K 0 and K 0 . The result is shown in Fig. 9.13 [181]. The result of a fit to these
data gives values for Φ +− and |η +− |, which are correlated with the values chosen
for m and τ S , respectively.
The correlation parameters are
δΦ +− = 0.30((m − 0.5301 × 10
10 s
−1 )
(9.146)
and
δ|η +− | = 0.09(τ S − 0.8934 × 10
−10 s) .
(9.147)