The present work continues a series of the KEDR measurements of the \(R\) value that started in 2010 at the VEPP-4M \(e^+e^-\) collider. By combining new data with our previous results in this energy ...range we measured the values of \(R_{\text{uds}}\) and \(R\) at nine center-of-mass energies between 3.08 and 3.72 GeV. The total accuracy is about or better than \(2.6\%\) at most of energy points with a systematic uncertainty of about \(1.9\%\). Together with the previous precise \(R\) measurement at KEDR in the energy range 1.84-3.05 GeV, it constitutes the most detailed high-precision \(R\) measurement near the charmonium production threshold.
Phys. Lett. B 738 (2014), 391-396 Using the inclusive photon spectrum based on a data sample collected at the
$J/\psi$ peak with the KEDR detector at the VEPP-4M $e^+e^-$ collider, we
measured the ...rate of the radiative decay $J/\psi\to\gamma\eta_{\rm c}$ as well
as $\eta_{\rm c}$ mass and width. Taking into account an asymmetric photon
lineshape we obtained $\Gamma^0_{\gamma\eta_{\rm c}}=2.98\pm0.18
\phantom{|}^{+0.15}_{-0.33}$ keV, $M_{\eta_{\rm c}} = 2983.5 \pm 1.4
\phantom{|}^{+1.6}_{-3.6}$ MeV/$c^2$, $\Gamma_{\eta_{\rm c}} = 27.2 \pm 3.1
\phantom{|}^{+5.4}_{-2.6}$ MeV.
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}\times\mathcal{B}_{\mu\mu} = 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}. \
We report results of experiments performed with the KEDR detector at the VEPP-4M \(e^+e^-\) collider. They include final results for the mass and other parameters of the \(J/\psi\), \(\psi(2S)\) and ...\(\psi(3770)\) and \(J/\psi\to\gamma\eta_c\) branching fraction determination.
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.
Phys. Lett. B731, 227 (2014) 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
$\Gamma_{ee}(J/\psi)/\Gamma_{\mu\mu}(J/\psi)=1.0022\pm0.0044\pm0.0048\
(0.65\%)$ 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.
Using the KEDR detector at the VEPP-4M \(e^+e^-\) collider, we have determined the values of \(R\) at thirteen points of the center-of-mass energy between 1.84 and 3.05 GeV. The achieved accuracy is ...about or better than \(3.9\%\) at most of the energy points with a systematic uncertainty less than \(2.4\%\).
Using the KEDR detector at the VEPP-4M \(e^+e^-\) collider, we have measured the values of \(R_{\text{uds}}\) and \(R\) at seven points of the center-of-mass energy between 3.12 and 3.72 GeV. The ...total achieved accuracy is about or better than \(3.3\%\) at most of energy points with a systematic uncertainty of about \(2.1\%\). At the moment it is the most accurate measurement of \(R(s)\) in this energy range.
Using the inclusive photon spectrum based on a data sample collected at the \(J/\psi\) peak with the KEDR detector at the VEPP-4M \(e^+e^-\) collider, we measured the rate of the radiative decay ...\(J/\psi\to\gamma\eta_{\rm c}\) as well as \(\eta_{\rm c}\) mass and width. Taking into account an asymmetric photon lineshape we obtained \(\Gamma^0_{\gamma\eta_{\rm c}}=2.98\pm0.18 \phantom{|}^{+0.15}_{-0.33}\) keV, \(M_{\eta_{\rm c}} = 2983.5 \pm 1.4 \phantom{|}^{+1.6}_{-3.6}\) MeV/\(c^2\), \(\Gamma_{\eta_{\rm c}} = 27.2 \pm 3.1 \phantom{|}^{+5.4}_{-2.6}\) MeV.
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 ...\(\Gamma_{ee}(J/\psi)/\Gamma_{\mu\mu}(J/\psi)=1.0022\pm0.0044\pm0.0048\ (0.65\%)\) 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.
