Accurate Measurement Of Branching Ratio Eta-] Neutrals/Eta-] Total

Summary  The branching ratioR=Γ(η→neutrals)/Γ(η→total) has been measured with counter techniques. The η-mesons were produced in the reaction π−+p→ n+MM at 0.8 GeV/c. A total of ∼24 000 η-events have been observed. The value found isR=(70.5±0.8)%. The 90% confidence level for the branching ratioR’=Γ(η→π0 γγ)/Γη→→ total is found to beR′≦10%.