A search for the process $e^+e^- to eta^prime$ has been performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The data were accumulated at the center-of-mass energy of $957.78pm 0.06$ MeV with an integrated luminosity of about 2.9 pb$^{
-1}$. For reconstruction of the $eta^prime$ meson five decay chains have been used: $eta^{prime}toetapi^+pi^-$ followed by the $eta$ decays to $gammagamma$ and $3pi^0 $, and $eta^{prime} to etapi^0pi^0$ followed by the $eta$ decays to $pi^+pi^-pi^0$, $gammagamma$, and $3pi^0$. As a result, the upper limit has been set on the $eta^prime$ electronic width: $Gamma_{eta^{prime}to e^+e^-} < 0.0020$ eV at the 90% confidence level.
In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider the cross section for the process $e^+e^-toetapi^+pi^-$ has been measured in the center-of-mass energy range from 1.22 to 2.00 GeV. Obtained results are in agreement with prev
ious measurements and have better accuracy. The energy dependence of the $e^+e^-toetapi^+pi^-$ cross section has been fitted with the vector-meson dominance model. From this fit the product of the branching fractions $B(rho(1450)toetapi^+pi^-)B(rho(1450)to e^+e^-)$ has been extracted and compared with the same products for $rho(1450)toomegapi^0$ and $rho(1450)topi^+pi^-$ decays. The obtained cross section data have been also used to test the conservation of vector current hypothesis.
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 $J/psitogammaeta_{rm c}$ as well as $eta_{rm c}$ mass and wi
dth. Taking into account an asymmetric photon lineshape we obtained $Gamma^0_{gammaeta_{rm c}}=2.98pm0.18 phantom{|}^{+0.15}_{-0.33}$ 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 $e^+e^-toetagamma$ cross section has been measured in the center-of-mass energy range 1.07--2.00 GeV using the decay mode $etato 3pi^0$, $pi^0to gammagamma$. The analysis is based on 36 pb$^{-1}$ of integrated luminosity collected with the SND de
tector at the VEPP-2000 $e^+e^-$ collider. The measured cross section of about 35 pb at 1.5 GeV is explained by decays of the $rho(1450)$ and $phi(1680)$ resonances.
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 $J/psitogammaeta_c$ branching fraction determination.
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.
We report the final results of a study of the psi(3770) meson using a data sample collected with the KEDR detector at the VEPP-4M electron-positron collider. The data analysis takes into account the interference between the resonant and nonresonant $
Dbar{D}$ production, where the latter is related to the nonresonant part of the energy-dependent form factor $F_D$. The vector dominance approach and several empirical parameterizations have been tried for the nonresonant $F_D^{NR}(s)$. Our results for the mass and total width of psi(3770) are M = 3779.2 ^{+1.8}_{-1.7} ^{+0.5}_{-0.7} ^{+0.3}_{-0.3} MeV, Gamma =24.9 ^{+4.6}_{-4.0} ^{+0.5}_{-0.6} ^{+0.2}_{-0.9} MeV, where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found: (1) Gamma_{ee} = 154 ^{+79}_{-58} ^{+17}_{-9} ^{+13}_{-25} eV, (2) Gamma_{ee} = 414 ^{+72}_{-80} ^{+24}_{-26} ^{+90}_{-10} eV. Our statistics are insufficient to prefer one solution to another. The solution (2) mitigates the problem of non-$Dbar{D}$ decays but is disfavored by potential models. It is shown that taking into account the resonance--continuum interference in the near-threshold region affects resonance parameters, thus the results presented can not be directly compared with the corresponding PDG values obtained ignoring this effect.
We report results of a search for narrow resonances in e+ e- annihilation at center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR detector at the VEPP-4M e+ e- collider. The upper limit on the leptonic width of a narrow resonance
Gamma(R -> ee) Br(R -> hadr) < 120 eV has been obtained (at 90 % C.L.).
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. Taki
ng 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 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/p
si->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.
