Measurement of the leptonic decay widths of the ϕ-meson with the KLOE detector

The ϕ-meson leptonic widths, Γee and Γμμ, are obtained, respectively, from the e+e− forward-backward asymmetry and the μ+μ− cross section around the ϕ-mass energy. We find Γee=1.32±0.05±0.03keV and ΓeeΓμμ=1.320±0.018±0.017keV. These results, compatible with Γee=Γμμ, provide a precise test of lepton universality. Combining the two results gives Γℓℓ(ϕ)=1.320±0.023keV.