A search for rare and forbidden decays of η-meson with GAMS-4π

Abstract

A search for the rare and forbidden neutral decays of η-meson with the GAMS-4π setup has been performed. The charge-exchange reaction at 32.5 GeV/c was used as a source of 3.7 ⋅ 10 6 η-mesons. At the 90% confidence level the following upper limits were obtained: B R ( η → 3 γ ) 1.6 ⋅ 10 −4 , B R ( η → 4 γ ) 2.8 ⋅ 10 −4 , B R ( η → π ° π ° ) 3.5 ⋅ 10 −4 , B R ( η → π ° π ° γ ) 1.7 ⋅ 10 −3 , B R ( η → π ° π ° γ γ ) 4.0 ⋅ 10 −3 , B R ( η → 3 π ° γ ) 2.4 ⋅ 10 −4 , B R ( η → 4 π ° ) 2.0 ⋅ 10 −5 .