We have improved by two orders of magnitude the limit currently available for the CPT violation parameter Re(
δ). To this purpose we have analyzed the full sample of neutral-kaon decays to e
πν ...recorded in the CPLEAR experiment, where the strangeness of the neutral kaons was tagged at production and decay time. An appropriate function of the measured decay rates, including information from the analysis of π
+π
− decay channel, gives directly Re(
δ). The result Re(
δ)=(3.0±3.3
stat±0.6
syst)×10
−4 is compatible with zero. Values for the parameters Im(
δ), Re(
x
−) and Im(
x
+) were also obtained.
Data from the CPLEAR experiment, together with the most recent world averages for some of the neutral-kaon parameters, were constrained with the Bell–Steinberger (or unitarity) relation, allowing the ...T-violation parameter Re(
ϵ) and the CPT-violation parameter Im(
δ) of the neutral-kaon mixing matrix to be determined with an increased accuracy: Re(
ϵ)=(164.9±2.5)×10
−5, Im(
δ)=(2.4±5.0)×10
−5. Moreover, the constraint allows the CPT-violation parameter for the neutral-kaon semileptonic decays, Re(
y), to be determined for the first time. The
ΔS≠
ΔQ parameters Re(
x
−) and Im(
x
+) are given with an increased accuracy. The quantity Re(
y+
x
−), which enters the T-violation CPLEAR asymmetry previously published, is determined to be (−0.2±0.3)×10
−3. The value obtained for Re(
δ) is in agreement with the one resulting from a previous unconstrained fit and has a slightly smaller error.
We report a measurement of the CP violation parameter
η
+− from the time-dependent asymmetry between the decay rates of initially tagged K
0 and
K
0
. The results are based on the complete data ...sample collected by the CPLEAR collaboration. With
Δm=(530.1±1.4)×10
7ℏs
−1 and
τ
S=(89.34±0.08) ps, the values obtained are |
η
+−|=(2.264±0.023
stat±0.026
syst±0.007
τ
S
)×10
−3 and
φ
+−=43.19°±0.53°
stat±0.28°
syst±0.42°
Δm
.
We report on a new measurement of the K
L–K
S mass difference
Δm using the CPLEAR full data sample of neutral-kaon decays to e
πν. The result is
Δm=(0.5295±0.0020
stat±0.0003
syst)×10
10 ℏ/s. It ...includes earlier data reported in R. Adler et al., CPLEAR Collaboration, Phys. Lett. B 363 (1995) 237. A measurement of the
ΔS=
ΔQ violating parameter Re(
x) is also obtained.
We test the Principle of Equivalence for particles and antiparticles, using CPLEAR data on tagged K
0 and
K
0
decays into
π
+
π
−. For the first time, we search for possible annual, monthly and ...diurnal modulations of the observables |
η
+−| and
φ
+−, that could be correlated with variations in astrophysical potentials. Within the accuracy of CPLEAR, the measured values of |
η
+−| and
φ
+− are found not to be correlated with changes of the gravitational potential. We analyze data assuming effective scalar, vector and tensor interactions, and we conclude that the Principle of Equivalence between particles and antiparticles holds to a level of 6.5, 4.3 and 1.8×10
−9, respectively, for scalar, vector and tensor potentials originating from the Sun with a range much greater than the distance Earth–Sun. We also study energy-dependent effects that might arise from vector or tensor interactions. Finally, we compile upper limits on the gravitational coupling difference between K
0 and
K
0
as a function of the scalar, vector and tensor interaction range.
A detailed description is given of the analysis of neutral kaons decaying to \pipi , based on the complete data sample collected with the CPLEAR experiment.Using a novel approach involving initially ...strangeness-tagged \kn\ and \knb ,the time-dependent decay rate asymmetry has been measured. This asymmetry, resulting from the interference between the \ks\and \kl\ decay amplitudes, has enabled both the magnitudeand phase of the CP-violation parameter, \ita , to be measured, with aprecision comparable to that of the current world average values.
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