Results from Searching for Muonium to Antimuonium Conversion

A new result from searching for muonium to antimuonium conversion is reported which sets an upper limit on the coupling constant in an assumed $(V-A) \times (V-A)$ type interaction of $G_{M\bar{M}} \leq 3\cdot 10^{-3} G_F$ ~ (90% C.L.). A particular Z_8 and a minimal 331 GUT model can be ruled out. Further new and stringent limits can be set for masses of bileptonic gauge bosons and $\lambda$ parameters in R-parity breaking supersymmetric models.