J/Ψ production via initial state radiation in e⁺e ^-→ μ⁺μ^-γ at an e ⁺e^- center-of-mass energy near 10.6 GeV

We have studied the process e⁺e ^-→μ⁺μ^-γ at a center-of-mass energy near the γ(4S) resonance for a μ⁺μ^- invariant mass range near the J/Ψ mass and measured the cross section σ(e⁺e^-→J/Ψ γt →μ ⁺μ^-γ). The data set, corresponding to an integrated luminosity of 88.4 fb^-1, was collected using the BABAR detector at the SLAC PEP-II collider. From the measured cross section we extract the product Γ(J/Ψ→e⁺e^-)B(J/ Ψ→μ⁺μ^-) = 0.330±0.008±0.007 keV. Using the world averages for B(J/Ψ →μ⁺μ ^- and B(J/Ψ→e⁺e^-), we derive the J/Ψ electronic and total widths: Γ(J/Ψ→e⁺e ^-) = 5.61 ±0.20 keV and Γ = 94.7 ± 4.4 keV.