ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2010, vol. 685, p. 134-140
Measurement of Γe e (J / ψ) ṡ B (J / ψ → e+ e-) and Γe e (J / ψ) ṡ B (J / ψ → μ+ μ-)
The products of the electron width of the J / ψ meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron-positron collider. The results areΓe e × Γe e / Γ = 0.3323 ± 0.0064 (stat.) ± 0.0048 (syst.) keV,Γe e × Γμ μ / Γ = 0.3318 ± 0.0052 (stat.) ± 0.0063 (syst.) keV . Their combinationsΓe e × (Γe e + Γμ μ) / Γ = 0.6641 ± 0.0082 (stat.) ± 0.0100 (syst.) keV,Γe e / Γμ μ = 1.002 ± 0.021 (stat.) ± 0.013 (syst.) can be used to improve the accuracy of the leptonic and full widths and test leptonic universality. Assuming eμ universality and using the world average value of the lepton branching fraction, we also determine the leptonic Γℓ ℓ = 5.59 ± 0.12 keV and total Γ = 94.1 ± 2.7 keV widths of the J / ψ meson. © 2010 Elsevier B.V. All rights reserved.