9 Symmetry Violations and Quark Flavour Physics
557
The electromagnetic calorimeter had the form of a barrel and was an assembly of
18 lead plates alternating with sampling chambers. It was located at radii between
75 cm and 100 cm. The calorimeter had a total thickness of ∼6 radiation lengths,
an energy resolution of σ E /E ≈ 13%/
√
E (E in GeV) and a position resolution
of ∼5 mm for the photon conversion points. The photon detection efficiency was
(90 ± 1)% for photon energies above 200 MeV. For photons with energies below
200 MeV the efficiency dropped significantly and was only about 60% for 100 MeV
photons.
All subdetectors were embedded in a 3.6 m long, 2 m diameter solenoid magnet,
which provided a 0.44 T uniform field.
9.5.5 Elucidation of CP Violation in K 0 Decays (I): Search for
m(ε /ε)
9.5.5.1 The Significance of the Phase +−
The phase of η +− , Φ +− = arg(η +− ), was a possible clue that would help to
disentangle the two components of CP violation, since
η +− = ε + ε
.
(9.128)
If ε , the parameter of direct CP violation, was comparable in size to ε, and if its
phase was orthogonal to ε, then the phase of η +− would deviate in a detectable way
from the phase of ε, which is mainly determined by the experimentally measurable
values of m and Γ S = 1/τ S (see Sect. 9.5.2):
arg(ε) = arctan
2
Γ S
+ Φ D = Φ SW + Φ D
(9.129)
With the present values of m and Γ S (Sect. 9.5.5.7), Φ SW = (43.4 ± 0.1) ◦ .
A significant deviation of the measured value of Φ +− from Φ SW would be
evidence for a nonvanishing component m(ε /ε) and against the superweak model
of CP violation.
9.5.5.2 Measurements of the Phase +− in Interference Experiments
Behind a Regenerator
The relative phase between the two amplitudes of the decays K L → π + π − and
K S → π + π − has been measured by two distinct methods.
The first consists of measuring the interference of the K L → π + π − amplitude
with the coherently regenerated K S → π + π − amplitude behind a slab of material
(the regenerator). The experiments require (a) the measurement of the π + π −
557
The electromagnetic calorimeter had the form of a barrel and was an assembly of
18 lead plates alternating with sampling chambers. It was located at radii between
75 cm and 100 cm. The calorimeter had a total thickness of ∼6 radiation lengths,
an energy resolution of σ E /E ≈ 13%/
√
E (E in GeV) and a position resolution
of ∼5 mm for the photon conversion points. The photon detection efficiency was
(90 ± 1)% for photon energies above 200 MeV. For photons with energies below
200 MeV the efficiency dropped significantly and was only about 60% for 100 MeV
photons.
All subdetectors were embedded in a 3.6 m long, 2 m diameter solenoid magnet,
which provided a 0.44 T uniform field.
9.5.5 Elucidation of CP Violation in K 0 Decays (I): Search for
m(ε /ε)
9.5.5.1 The Significance of the Phase +−
The phase of η +− , Φ +− = arg(η +− ), was a possible clue that would help to
disentangle the two components of CP violation, since
η +− = ε + ε
.
(9.128)
If ε , the parameter of direct CP violation, was comparable in size to ε, and if its
phase was orthogonal to ε, then the phase of η +− would deviate in a detectable way
from the phase of ε, which is mainly determined by the experimentally measurable
values of m and Γ S = 1/τ S (see Sect. 9.5.2):
arg(ε) = arctan
2
Γ S
+ Φ D = Φ SW + Φ D
(9.129)
With the present values of m and Γ S (Sect. 9.5.5.7), Φ SW = (43.4 ± 0.1) ◦ .
A significant deviation of the measured value of Φ +− from Φ SW would be
evidence for a nonvanishing component m(ε /ε) and against the superweak model
of CP violation.
9.5.5.2 Measurements of the Phase +− in Interference Experiments
Behind a Regenerator
The relative phase between the two amplitudes of the decays K L → π + π − and
K S → π + π − has been measured by two distinct methods.
The first consists of measuring the interference of the K L → π + π − amplitude
with the coherently regenerated K S → π + π − amplitude behind a slab of material
(the regenerator). The experiments require (a) the measurement of the π + π −