Further results from the interference of K S and K L in the π +π − decay modes

Abstract

Previous measurements on K ° decay and the interference of K L and K S in the π +π − decay modes have been extended. We find that the interference term has the predicted coefficient with an experimental uncertainty of about 15%, that the K L - K S mass difference is ± (0.445 ± 0.034), the phase ϕ = ϕη - ϕf is ± (1.41 ± 0.18) and we find no evidence for the lepton pair decays of K L. With 90% confidence Γ L.μ +μ − /Γ L < 2 × 10 −4 Γ L, e + e −/Γ L < 1.6 × 10 −4.