New bounds from a search for muonium to antimuonium conversion

A new upper limit for the probability of spontaneous muonium to antimuonium conversion was established at P-M (M over bar) less than or equal to 8.3 x 10(-11) (90% C.L.) in 0.1 T magnetic field, which implies consequences for speculative extensions to the standard model. Coupling parameters in R-parity-violating supersymmetry and the mass of a flavor diagonal bileptonic gauge boson can be significantly restricted. A Z(8) model with radiative mass generation through heavy lepton seed and the minimal version of 331 models are disfavored. [S0031-9007(98)08068-5].