[en] Expressions are given for the calculation of heavy lepton event rates and the background muon fluxes for planning the search for heavy leptons via a K/sub L/⁰-type experiment

No abstract available

No abstract available

[en] We report the first observation of the decay K_L→π^Oγγ where 21 events have been found with an expected background of 1.5 ± 0.9. The corresponding branching ratio for decays with an invariant mass m_γγ above 280 MeV is (2.1 ± 0.6) x 10^-6. Implications of this result on the CP conserving contribution to K_L→π^Oe⁺e^- have been studied. The observation of 2 events of the decay K_L→e⁺e^-e⁺e^- mode with a negligible background is also reported. A branching ratio of (4±3) x 10^-8 has been derived, consistent with theoretical prediction

[en] BNL-E871 is a two arm rare kaon decay spectrometer at the BNL-AGS. The experiment uses a neutral kaon beam to search for the forbidden decay K_L⁰ → μe. The previous experiment (E791) in the same beam line allowed the neutral beam to pass through a gap in the spectrometer. For E871 it seems more advantageous to dispose of the beam in a compact beam dump located in the middle of the spectrometer. The elimination of the beam allows increase in acceptance by eliminating the gap in the downstream spectrometer, reduces accidentals in the trigger, and in the downstream particle identification detectors

[en] In a search for Lepton Flavor Violation in the decay K⁰_L → μe conducted at the Brookhaven National Lab. Alternating Gradient Synchrotron facility, no candidate K⁰_L → μe events were found and a 90% confidence level upper limit on the branching ratio B(K⁰_L → μe) < 8.6 x 10^-11 was set

[en] Soft-gluon exchange as manifestation of the strong interaction at long distance provides color degrees of freedom of internal quarks in K_L → γγ that enhance the amplitude calculated in the standard electroweak gauge model. The enhancement obtained is sufficient to account for the observed decay amplitude. (author). 13 refs, 1 fig

[en] We discuss the rare decay K_L→π⁰γγ. Although the recently measured 2γ-invariant-mass distribution is in quite good agreement with the lowest-order chiral perturbation theory prediction, there seems to be a discrepancy with the calculated branching ratio. We extend the previous computations to next-to-leading order, O(p⁶). The two dominant mechanisms at this order are emphasized: the two-pion intermediate state and vector meson exchange. (authors)

[en] A new measurement of the K_L→e⁺e^-γγ branching ratio was carried out in Fermilab experiment E799. We observed 58 K_L→e⁺e^-γγ events. The measured branching ratio is B(K_L→e⁺e^-γγ, E_γ^*>5 MeV) = [6.5±1.2 (stat) ±0.6 (syst)] x10^-7

[en] We show that states of the type vertical strokeK_S>, vertical strokeK_L> differ at early time periods from the eigenstates vertical strokes^t→0>, vertical strokel^t→0> of the effective Hamiltonian H_parallel(t) governing the time evolution in the subspace spanned by the state vectors vertical strokeK⁰>, vertical strokeanti K⁰> of K⁰, anti K⁰ and other similar particles, and coincide with their eigenstates vertical strokes^t→∞>, vertical strokel^t→∞> in the long time region. It is shown that the exponential decay law of K_S or K_L type particles should be modified by multiplying it by some factor, which is equal to 1 only if there are no CP-violations. (orig.)