Search for rare muon decays with the Crystal Box detector

A search with the Crystal Box detector shows no evidence for the lepton-family-number-nonconserving decays {μ}{→}e{γ}, {μ}{→}e{γ}{γ}, or {μ}{→}eee. The search provides upper limits for the branching ratios of {Γ}({μ}{→}e{γ})/{Γ}({μ}{→}evv{})4.9×{}10^-11 (90% C.L.), {Γ}({μ}{→}e{γ}{γ})/{Γ}({μ}{→}evv{})7.2×{}10^-11 (90% C.L.), and {Γ}({μ}{→}eee)/{Γ}({μ}{→}evv{})3.510^-11 (90% C.L.). In addition, a limit for the emission of a light scalar or pseudoscalar boson in radiative muon decay is given.