0 SEARCH FOR ψ (2S ) → Λ Λ Ks

Abstract

Using 14 million ψ(2S) decay events registered by Beijing Spectrometer II commonly known as BESII at Beijing Electron Positron Collider (BEPC), we have performed ̄ 0 detailed study of ψ(2S) → ΛΛKs (a strangeness and isospin violating process), to look for any hint beyond the ’Standard Model’. Finding no obvious signal, we report, first time, an upper limit of 9.3 × 10−5 at 90% confidence level, for the branching fraction.