Search

Abstract: A threshold Cherenkov counter based on dense aerogel with refraction index n=1.13 is described. This counter is used for kaon identification at momenta below 1GeV/c in the SND detector, which takes data at the VEPP-2000 e+e− collider. The results of measurements of the counter efficiency using electrons, muons, pions, and kaons produced in e+e− annihilation are presented. [Copyright &y& Elsevier]

Abstract 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 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. [ABSTRACT FROM AUTHOR]

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 % . [ABSTRACT FROM AUTHOR]

Using the KEDR detector at the VEPP-4M e + e − collider, we have measured the values of R 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. [ABSTRACT FROM AUTHOR]

We present the analysis of all KEDR data on the determination of J / ψ and ψ ( 2 S ) masses. The data comprise six scans of J / ψ and seven scans of ψ ( 2 S ) which were performed at the VEPP-4M e + e − collider in 2002–2008. The beam energy was determined using the resonance depolarization method. The detector and accelerator conditions during scans were very different that increases the reliability of the averaged results. The analysis accounts for partial correlations of systematic uncertainties on the masses. The following mass values were obtained: M J / ψ = 3096.900 ± 0.002 ± 0.006 MeV , M ψ ( 2 S ) = 3686.099 ± 0.004 ± 0.009 MeV . These results supersede our previous measurements published in 2003 and 2012. [ABSTRACT FROM AUTHOR]

Using the inclusive photon spectrum based on a data sample collected at the J / ψ peak with the KEDR detector at the VEPP-4M e + e − collider, we measured the rate of the radiative decay J / ψ → γ η c as well as η c mass and width. Taking into account an asymmetric photon lineshape we obtained Γ γ η c 0 = 2.98 ± 0.18 − 0.33 + 0.15 keV , M η c = 2983.5 ± 1.4 − 3.6 + 1.6 MeV / c 2 , Γ η c = 27.2 ± 3.1 − 2.6 + 5.4 MeV . [ABSTRACT FROM AUTHOR]

Abstract: We report the final results of a study of the meson using a data sample collected with the KEDR detector at the VEPP-4M electron–positron collider. The data analysis takes into account interference between the resonant and nonresonant production, where the latter is related to the nonresonant part of the energy-dependent form factor . The vector dominance approach and several empirical parameterizations have been tried for the nonresonant . Our results for the mass and total width of are where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found: Our statistics are insufficient to prefer one solution to another. The Solution (2) mitigates the problem of non- 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 cannot be directly compared with the corresponding PDG values obtained ignoring this effect. [Copyright &y& Elsevier]

Abstract: We report results of a search for narrow resonances in annihilation at center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR detector at the VEPP-4M collider. The upper limit on the leptonic width of a narrow resonance has been obtained (at 90% C.L.). [Copyright &y& Elsevier]