Searches for rare and forbidden neutral decays of η mesons at the GAMS-4π facility

Abstract

Searches for rare and forbidden neutral decays of {eta} mesons are performed at the GAMS-4{pi} facility. A charge-exchange reaction at an initial momentum of 32.5 GeV/c was used as a source of 3.7 x 10{sup 6}{eta} mesons. The following upper limits are established at a 90% confidence level: Br({eta} {sup {yields}} 3{gamma}) < 1.6 x 10{sup -4}, Br({eta} {sup {yields}} 4{gamma}) < 2.8 x 10{sup -4}, Br({eta} {sup {yields}} {pi}{sup 0}{pi}{sup 0}) < 3.5 x 10{sup -4}, Br({eta} {sup {yields}} {pi}{sup 0}{pi}{sup 0}{gamma}) < 1.7 x 10{sup -3}, Br({eta} {sup {yields}} {pi}{sup 0}{pi}{sup 0}{gamma}{gamma}) < 4.0 x 10{sup -3}, Br({eta} {sup {yields}} 3{pi}{sup 0}{gamma}) < 2.4 x 10{sup -4}, and Br({eta} {sup {yields}} 4{pi}{sup 0}) < 2.0 x 10{sup -5}.