New Bounds from Searching for Muonium to Antimuonium Conversion

Abstract

A new upper limit for the probability of spontaneous muonium to antimuonium conversion was established at ${\mathrm{P}}_{\mathrm{M}\bar{\mathrm{M}}}\le 8.2\cdot 10^{-11}$ (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 flavour 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-GUT models are ruled out.