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Register a new userMeasurement of J/psi leptonic width with the KEDR detector
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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.
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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.
Using a data set of 2.93 fb$^{-1}$ taken at a center-of-mass energy of $sqrt{s}$ = 3.773 GeV with the BESIII detector at the BEPCII collider, we measure the process $e^+e^-rightarrow J/psigammarightarrow mu^+mu^-gamma$ and determine the product of the branching fraction and the electronic width $mathcal B_{mumu}cdot Gamma_{ee} = (333.4 pm 2.5_{rm stat} pm 4.4_{rm sys})$~eV. Using the earlier-published BESIII result for $mathcal B_{mumu}$ = (5.973 $pm$ 0.007$_{rm stat}$ $pm$ 0.037$_{rm sys}$)%, we derive the $J/psi$ electronic width $Gamma_{ee}$~= (5.58 $pm$ 0.05$_{rm stat}$ $pm$ 0.08$_{rm sys}$) keV.
We present a study of the inclusive photon spectra from 5.9 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV, G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.
We present a study of the inclusive photon spectrum from 6.3 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of the radiative decay J/psi -> eta_c gamma, eta_c width and mass. Taking into account an asymmetric photon line shape we obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4 +- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.
The $phi$(1020) meson leptonic width has been determined from the combined analysis of 4 major decay modes of the resonance ($phito K^+ K^-,K^0_LK^0_S,pi^+pi^-pi^0,etagamma$) studied with the CMD-2 detector at the VEPP-2M $e^+e^-$ collider. The following value has been obtained: $Gamma(phito e^+e^-) = 1.235pm 0.006pm 0.022$ keV. The $phi(1020)$ meson parameters in four main decay channels have been also recalculated: $B(phito K^+K^-) = 0.493pm 0.003pm 0.007$, $B(phito K_LK_S) = 0.336pm 0.002pm 0.006$, $B(phitopi^+pi^-pi^0) = 0.155pm 0.002pm 0.005$, $B(phitoetagamma) = 0.0138pm 0.0002pm 0.0002$.
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