Search For Rare Decays Of Eta-Mesons And Eta'-Mesons, And For Light Higgs Particles

The upper limits for the branching ratios of rare η, η′ decays have been obtained: BR( η → π 0 μ + − )<6×10 −6 , BR( η ′→ ημ + μ − )<1.5×10 −5 , BR( η ′→ π 0 μ + μ − )<7×10 −5 and BR( η → π 0 μ + μ − γ )<3×10 −6 (90% c.l.). These are several orders of magnitude lower than the previous limits. The analysis of the decay η ′→ ημ + μ − excludes the existence of light Higgs particles with a mass lower than 409 MeV/ c 2 .