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.
We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of
K
0
transforming into K
0 and K
0 into
K
0
as a function of the neutral-kaon ...eigentime
t. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at time
t=0 was tagged by the kaon charge in the reaction
p
p
→
K
±π
∓
K
0
(
K
0
)
at rest, whereas the strangeness of the kaon at the decay time
t=
τ was tagged by the lepton charge in the final state. An average decay-rate asymmetry
〈
R(
K
0
t=0→
e
+
π
−
ν
t=τ)−R(
K
0
t=0→
e
−
π
+
ν
t=τ)
R(
K
0
t=0→
e
+
π
−
ν
t=τ)+R(
K
0
t=0→
e
−
π
+
ν
t=τ)
〉=(6.6±1.3
stat
±1.0
syst
)×10
−3
was measured over the interval
1
τ
S
<τ<20
τ
S
, thus leading to evidence for time-reversal non-invariance.
Physics at CPLEAR Angelopoulos, A.; Apostolakis, A.; Aslanides, E. ...
Physics reports,
2003, 2003-1-00, Letnik:
374, Številka:
3
Journal Article
Recenzirano
LEAR offered unique opportunities to study the symmetries which exist between matter and antimatter. At variance with other approaches at this facility, CPLEAR was an experiment devoted to the study ...of
CP
,
T
and
CPT
symmetries in the neutral-kaon system. A variety of measurements allowed us to determine with high precision the parameters which describe the time evolution of the neutral kaons and their antiparticles, including decay amplitudes, and the related symmetry properties. Limits concerning quantum-mechanical predictions (EPR, coherence of the wave function) or the equivalence principle of general relativity have been obtained. An account of the main features of the experiment and its performances is given here, together with the results achieved.
A fast pattern recognition system for HEP experiments, based on artificial neural network algorithms (ANN), has been realized with standard electronics. The multiplicity and location of tracks in an ...event are determined in less than 75 ns. Hardware modules of this first level trigger were extensively tested for performance and reliability with data from the CPLEAR experiment.
We apply a forward dispersion relation to the regeneration amplitude for kaon scattering on \(^{12}\)C using all available data. The CPLEAR data at low energies allow the determination of the net ...contribution from the subthreshold region which turns out to be much smaller than earlier evaluations, solving a long standing puzzle.
The DIRAC experiment at CERN has achieved a sizeable production of Ie super(+Ie) super(-) atoms and has significantly improved the precision on its lifetime determination. From a sample of 21 227 ...atomic pairs, a 4% measurement of the S-wave IeIe scattering length difference inline image has been attained, providing an important test of Chiral Perturbation Theory.
The DIRAC experiment at CERN has achieved a sizeable production of
π
+
π
−
atoms and has significantly improved the precision on its lifetime determination. From a sample of 21 227 atomic pairs, a 4% ...measurement of the S-wave
ππ scattering length difference
|
a
0
−
a
2
|
=
(
0.2533
−
0.0078
+
0.0080
|
stat
|
syst
−
0.0073
+
0.0078
)
M
π
+
−
1
has been attained, providing an important test of Chiral Perturbation Theory.
We report the results of the CPLEAR experiment on CP-, T-, and CPT-symmetries in the neutral kaon system. CP-violation parameters are given for the K
0,
K
0 → 2π, 3π
decay channels. For the first ...time, T-violation is measured by a direct method using semileptonic decays. The CPT symmetry is tested through the parameters Im(δ) with a precision of 10
−5 and Re(δ) with a precision of a few 10
−4. With these two measurements, the difference in mass and width of K
0 and
K
0
are bound to within 10
−18 GeV. In the limit of CPT invariance in the neutral kaon decays, the K
0 and
K
0
masses are equal within 10
−19 GeV.
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