Measurement of main parameters of the ψ(2S) resonance
hep-ex
/ Authors
V. V. Anashin, V. M. Aulchenko, E. M. Baldin, A. K. Barladyan, A. Yu. Barnyakov, M. Yu. Barnyakov, S. E. Baru, I. Yu. Basok, O. L. Beloborodova, A. E. Blinov
and 72 more authors
V. E. Blinov, A. V. Bobrov, V. S. Bobrovnikov, A. V. Bogomyagkov, A. E. Bondar, A. R. Buzykaev, S. I. Eidelman, D. N. Grigoriev, Yu. M. Glukhovchenko, V. V. Gulevich, D. V. Gusev, S. E. Karnaev, G. V. Karpov, S. V. Karpov, T. A. Kharlamova, V. A. Kiselev, V. V. Kolmogorov, S. A. Kononov, K. Yu. Kotov, E. A. Kravchenko, V. N. Kudryavtsev, V. F. Kulikov,
/ Abstract
A high-precision determination of the main parameters of the ψ(2S) resonance has been performed with the KEDR detector at the VEPP-4M e^{+}e^{-} collider in three scans of the ψ(2S) -- ψ(3770) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the ψ(2S) we obtained the mass value M = 3686.114 +- 0.007 +- 0.011 ^{+0.002}_{-0.012} MeV and the product of the electron partial width by the branching fraction into hadrons Γ_{ee}*B_{h} = 2.233 +- 0.015 +- 0.037 +- 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference effects in the cross section of the single-photon e^{+}e^{-} annihilation to hadrons explicitly considered in this work. Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the ψ(2S): Γ_{ee} =2.282 +- 0.015 +- 0.038 +- 0.021 keV, Γ= 296 +- 2 +- 8 +- 3 keV. These results are consistent with and more than two times more precise than any of the previous experiments.