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Register a new userMeasurement of the ratio of the leptonic widths $Gamma_{ee}/Gamma_{mumu}$ for the $J/psi$ meson
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The ratio of the electron and muon widths of the $J/psi$ meson has been measured using direct $J/psi$ decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result $Gamma_{ee}(J/psi)/Gamma_{mumu}(J/psi)=1.0022pm0.0044pm0.0048 (0.65%)$ is in good agreement with the lepton universality. The experience collected during this analysis will be used for a $J/psi$ lepton width determination with up to 1% accuracy.
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The product of the electronic width of the $psi(2S)$ meson and the branching fraction of its decay to the muon pair was measured in the $e^{+}e^{-} to psi(2S) to mu^{+}mu^{-}$ process using nine data sets corresponding to an integrated luminosity of about 6.5 pb$^{-1}$ collected with the KEDR detector at the VEPP-4M electron-positron collider: [ Gamma_{ee}timesmathcal{B}_{mumu} = 19.3 pm 0.3 pm 0.5 ~text{eV}. ] Adding the previous KEDR results on hadronic and leptonic channels, the values of the $psi(2S)$ electronic width were obtained under two assumptions: either with the assumption of lepton universality [ Gamma_{ee} = 2.279 pm 0.015 pm 0.042 ~text{keV} ] or without it, summing up hadronic and three independent leptonic channels: [ Gamma_{ee} = 2.282 pm 0.015 pm 0.042 ~text{keV}. ]
The products of the electron width of the J/psi 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 are Gamma_{ee}(J/psi)*Br(J/psi->e^+e^-)=(0.3323pm0.0064pm0.0048) keV, Gamma_{ee}(J/psi)*Br(J/psi->mu^+mu^-)=(0.3318pm0.0052pm0.0063) keV. Their combinations Gamma_{ee}times(Gamma_{ee}+Gamma_{mumu})/Gamma=(0.6641pm0.0082pm0.0100) keV, Gamma_{ee}/Gamma_{mumu}=1.002pm0.021pm0.013 can be used to improve theaccuracy of the leptonic and full widths and test leptonic universality. Assuming emu universality and using the world average value of the lepton branching fraction, we also determine the leptonic Gamma_{ll}=5.59pm0.12 keV and total Gamma=94.1pm2.7 keV widths of the J/psi meson.
The product of the electronic width of the $J/psi$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $Gamma_{ee}(J/psi) = 5.550 pm 0.056 pm 0.089 , text{keV}, $ $Gamma_{ee}(J/psi) cdot mathcal{B}_text{hadrons}(J/psi) = 4.884 pm 0.048 pm 0.078 , text{keV}, $ $Gamma_{ee}(J/psi) cdot mathcal{B}_{ee}(J/psi) = 0.3331 pm 0.0066 pm 0.0040 , text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/psi$ meson: $Gamma = 92.94 pm 1.83 , text{keV}.$ These results are consistent with the previous experiments.
We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M $e^{+}e^{-}$ collider. The measured values of the J/psi parameters are: Gamma_{ee}timesGamma_{ee}/Gamma = 0.3323 pm 0.0064 (stat.) pm 0.0048 (syst.) keV Gamma_{ee}timesGamma_{mumu}/Gamma=0.3318 pm 0.0052 (stat.) pm 0.0063 (syst.) keV. Assuming $emu$ universality and using the table value of the branching ratios the leptonic Gamma_{ll}= 5.59 pm 0.12 keV width and the total Gamma=94.1 pm 2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow resonance.
The resonance parameters of the excited psi-family resonances, namely the psi(4040), psi(4160), and psi(4415), were determined by fitting the R-values measured by experiments. It is found that the previously reported leptonic partial widths of these states were merely one possible solutions among a four-fold ambiguity. By fitting the most precise experimental data on the R-values measured by the BES collaboration, this work presents all four sets of solutions. These results may affect the interpretation of the charmonium and charmonium-like states above 4GeV/c^2.
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