Improved search for two body muon decay μ+→e+XH

Charged lepton flavor violating muon decay μ⁺→e⁺X_H , where X_H is a massive neutral boson, was sought by searching for extra peaks in the muon decay μ⁺→e⁺ν ν ¯ energy spectrum in the m_XH mass region 47.8 - 95.1 MeV /c² . No signal was found and 90% confidence level upper limits were set on the branching ratio Γ (μ⁺→e⁺X_H)/Γ (μ⁺→e⁺ν ν ¯ ) at the level of 10^-5 for this region.