0000000000310071
AUTHOR
R. Werthenbach
showing 11 related works from this author
A measurement of the decay KL→π0γγ
1992
Abstract The full data set of the experiment NA31 at CERN has been used to analyse the decay mode KL→π0γγ. A signal of 63 events has been observed with an estimated background of 6.0±1.7 events, corresponding to a branching ratio of (1.7±0.3)×10−6 consistent with our previous result based on partial statistics. The invariant mass spectrum of the two photons is found to be consistent with chiral perturbation theory, and the decay is dominated by the J = 0 two photon state.
Measurement of the K-S mean lifetime from pi(+)pi(-) and pi(0)pi(0) decays using K-L decays to determine the acceptance
1997
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.
Observation of the decay KL→π0γγ
1990
Abstract The decay mode K L → π 0 γγ has been observed with a signal of 21 events and an expected background of 1.5±0.9 events. A branching ratio for decays with invariant γγ masses above 280 MeV of (2.1±0.6)×10 −6 is calculated. This result is compared with the values estimated from theoretical models and has implications for the CP conserving contribution to K L → π 0 e + e − decay.
Measurement of the decay KL→e+e−γγ
1998
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
2016
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
1995
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
1995
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.
Determination of the branching ratiosΓ(K L→3π0)/Γ(K L→π+ - 0) andΓ(K L→3π0)/Γ(K L→πev)
1995
Improved branching ratios were measured for theKL→3π0 decay in a neutral beam at the CERN SPS with the NA31 detector: $$\Gamma ({\rm K}_L \to 3\pi ^0 )/\Gamma ({\rm K}_L \to \pi ^ + \pi ^ - \pi ^0 ) = 1.611 \pm 0.037$$ and $$\Gamma ({\rm K}_L \to 3\pi ^0 )/\Gamma ({\rm K}_L \to \pi ev) = 0.545 \pm 0.010.$$ From the first number an upper limit for ΔI=5/2 and ΔI=7/2 transitions in neutral kaon decay is derived. Using older results for the Ke3/Kμ3 fraction, the 3π0 branching ratio is found to beΓ(K L →3π0)/Γ tot =(0.211±0.003), about a factor three more precise than from previous experiments.
Measurement of the rate of the decay KL→e+e−γ and observation of a form factor in this decay
1990
Abstract A large sample of Dalitz decays, K L → e + e − γ , has been observed. The branching ratio is Γ(K L →e + e − γ) Γ(K L → all )=(9.2±0.5±0.5)×10 −6 in good agreement with theoretical predictions. We observe an enhancement at high masses in the distribution of the invariant electron-positron pair mass, compared to the distribution expected from QED. This excess is interpreted as being due to virtual mesons contributing to the photon propagator.
Observation of the decay KLO→ e+e−ep+e−
1991
Abstract Two events with the characteristic of the decay K L O → e + e − e − have been observed with a negligible expected background from which a branching ratio of (4±3)×10 −8 is derived. This result is consistent with values estimated from theoretical models based on the double internal conventional of the decay K L O → γγ .
A new measurement of direct CP violation in the neutral kaon system
1993
A new measurement of the ratio of the CP-violating amplitudes for $K_{L} \to 2\pi^{0}$ and $K_{L} \to \pi^{+}\pi^{-}$ is reported. The measured value for $\Re = |\eta_{00} / \eta_{ +-}|^{2}$ is $0.9878 \pm 0.0026 \pm 0.0030$, where the first error is the statistical uncertainty and the second is the estimate of the systematic uncertainty. This gives a value for the parameter describing direct CP violation: $\Re$ $\epsilon'/\epsilon = (2.0 \pm 0.7) \times 10^{−3}$ .