Observation of the decay ψ(2S) → K0SK0L

The decay ψ(25) → K 0 SK 0 L is observed using ψ(2S) data collected with the Beijing Spectrometer at the Beijing Electron-Positron Collider; the branching fraction is determined to be B(ψ(2S) → K 0 SK 0 L) = (5.24 ′ 0.47 ′ 0.48) X 10 - 5 . Compared with J/ψ → K 0 SK 0 L, the ψ(2S) branching fraction is enhanced relative to the prediction of the perturbative QCD 12% rule. The result, together with the branching fractions of ψ(2S) decays to other pseudoscalar meson pairs (π + π - and K + K - ), is used to investigate the relative phase between the three-gluon and the one-photon annihilation amplitudes of ψ(2S) decays.