Leptonic decays of vector mesons and a possible μ⁺μ⁻ resonance

Abstract

The possible existence of a vector leptonic resonance (χ⁰) in the μ⁺μ⁻ system is considered. We discuss the effect such a resonance would have on the g factor of the muon and also on the ratio of the partial widths of the muonic and electronic decay modes (R_V = Γ (V → μ⁺μ⁻)/G (V → e⁺ e⁻)) of the neutral vector mesonsρ ⁰,ω,ϕ,ψ, andψ′. From the experimental values of R_ρ and R_ϕ, the following values are obtained for the mass, coupling constant, and partial decay widths of the resonance: M = 872 ± 60 MeV, f²/4π = 4 ± 2) ·10⁻⁴, Γ(χ ⁰ →μ ⁺ μ ⁻) = 0.12±0.06 MeV, and Γ (χ⁰ → ρ⁰ → π⁺π⁻) = 0.13±0.06 MeV.