0000000000248310
AUTHOR
J. Scheidt
First measurement of the rate K0L → πμνγ
Abstract In a preliminary version of the NA48 experiment at the CERN SPS, in which an iron-scintillator sandwich calorimeter was used as a photon detector, the ratio of K L → πμνγ and K L → πμν decays was measured. The branching ratio BR(K L →πμνγ, E γ ∗ ≥30 MeV )/(K L → πμν ) is found to be (2.08±0.17 +0.16 −0.21 )×10 −3 , where the first error is statistical and the second systematic. The result is in agreement with theoretical predictions.
Measurement of the K-S mean lifetime from pi(+)pi(-) and pi(0)pi(0) decays using K-L decays to determine the acceptance
A precision measurement of the KS mean lifetime has been performed by comparing, in the same experimental setup, the distributions of two-pion decays of neutral kaons produced by high energy proton-beryllium interactions in two targets at a relative distance variable between 112 and 160 m. The value obtained combining the results from π+π- and π0π0 decays is τS = (0.8971 ± 0.0021) 10-10 s. © Springer-Verlag 1997.
Measurement of the decay KL→e+e−γγ
The full data set of the NA31 experiment at CERN has been used to analyse the decay mode KOL → e+ e-γγ. A signal of 47 events has been observed with an estimated background of 6.9 events. The total number of kaon decays in the decay volume was determined to be (2.1 ± 0.1stat) · 109. This corresponds to a branching ratio of (8.0 ± 1.5+1.4-1.2)· 10-7. © 1998 Published by Elsevier Science B.V.
Measurement of the branching ratio of the double Dalitz decayK L →e+e−e+e− and the CP parity of theK L -meson
Data from the NA31 experiment at CERN have been used to measure the branching ratio of the double Dalitz decay of the long-lived neutral kaon. Eight events have been found with negligible background. The measured distribution of the angle between the planes of the two e+e--pairs favours a CP=-1 state for the long-lived neutral kaon. © 1995 Springer-Verlag.
A test of chiral perturbation theory from the measurement of the decay KS → γγ
Data from NA31 experiment at CERN have been used to measure the decay KS → γγ. From 69 candidate events of the type K0 → γγ, 52 events can be attributed to KL → γγ and one event is expected from background processes. The ratio of the relative decay widths R = Γ(KS → γγ)Γ(KL → γγ) is measured to be R = 2.2 ± 1.0(stat.) ± 0.3(syst.) ± 0.2(ext.) where the external systematic error is due to the experimental uncertainty in the branching ratio of the decay KL → γγ. This translates into a branching ratio of BR(KS → γγ) = (2.2 ± 1.1) × 10−6. If these data are combined with the published data from an earlier data taking period with the same experiment, the ratio R is determined to be R = 2.35 ± 0.7…
Search for the decay KL → 3γ
Abstract Data from the NA31 experiment at the CERN SPS have been used for the first search for the decay mode KL → 3γ. Seven events have been found with an estimated background of 6.7 ± 1.5 events. The corresponding upper limit for the branching ratio is Γ(K L → 3γ) Γ(K L → all ) = 2.4 × 10 −7 at the 90% confidence level, assuming a phase-space decay distribution.
Measurement of the decay rate and form factor parameter in the decay KL→e+e−γ
Abstract The decay rate of the neutral K meson KL→e+e−γ has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is Γ(KL→e+e−γ)/Γ(KL→all) = (1.06±0.02stat±0.02sys±0.04calc)×10−5. The parameter α K ∗ describing the relative strength of the two contributing amplitudes to this decay through intermediate pseudoscalar or vector mesons was measured to be α K ∗ =−0.36±0.06stat±0.02sys.
Rare decays of neutral kaons
This report summarises results on rare decays of neutral kaons. Three different classes of decays are discussed. Most of the examples were taken from results of the NA31 experiment. Therefore, the experiment is described in the first chapter. Subject of the second chapter are decays allowing to measure the CP-violation (i.e. KL → π0 e+e−) and some related decays (i.e. KL → γγe+e− as the worst background process to KL → π0 e+e−). In the third chapter searches for decays which are forbidden or highly suppressed in the Standard model are discussed. The forth chapter describes the measurements of decays allowing to test low energy QCD. The last chapter lists the prospects for the future of stud…