37 research outputs found

    Radiative decays of light vector mesons

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    The new data on ρ,ω,ϕ\rho,\omega,\phi radiative decays into π0γ,ηγ,ηγ\pi^0\gamma,\eta\gamma,\eta'\gamma from SND experiment at VEPP-2M e+ee^+e^- collider are presented.Comment: 5 pages, 2 figures, talk given at 8th International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199

    Search for direct production of a2(1320) and f2(1270) mesons in e+e- annihilation

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    A search for direct production of C-even resonances a2(1320) and f2(1270) in e+e- annihilation was performed with SND detector at VEPP-2M e+e- collider. The upper limits of electronic widths of these mesons were obtained at 90% confidence level: Gamma(a2(1320) \to e+e-) < 0.56 eV, Gamma(f2(1270) \to e+e-) < 0.11 eV.Comment: 6 pages, 5 figures, 1 table. Submitted to Phys. Lett.

    The process e+eπ+ππ0e^+e^-\to\pi^+\pi^-\pi^0 in the energy range 2E_0=1.04 - 1.38 GeV

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    In the experiment with the SND detector at VEPP-2M e^+e^- collider the process e+eπ+ππ0e^+e^-\to\pi^+\pi^-\pi^0 was studied in the energy range 2E_0 from 1.04 to 1.38 GeV. A broad peak was observed with the visible mass Mvis=1220±20M_{vis}=1220\pm 20 MeV and cross section in the maximum σ04\sigma_0\simeq 4 nb. The peak can be interpreted as a ω\omega-like resonance ω(1200)\omega (1200).Comment: 10 pages LATEX and 5 figure

    Role of Scalar Meson Resonances in $K_{L}^{0} \rightarrow \pi^{0} \gamma \gamma Decay

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    Corrections to KL0π0γγK_{L}^{0}\rightarrow \pi^{0} \gamma \gamma decay induced by scalar meson exchange are studied within chiral perturbation theory. In spite of bad knowledge of scalar-mesons parameters, the calculated branching ratio can be changed by a few percent.Comment: 18 pages of text, 2 figures (available upon request); preprint IJS-TP-16-94 , TUM-T31-63-94

    Primakoff effect in eta-photoproduction off protons

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    We analyse data on forward eta-meson photoproduction off a proton target and extract the eta to gamma gamma decay width utilizing the Primakoff effect. The hadronic amplitude that enters into our analysis is strongly constrained because it is fixed from a global fit to available gamma p to p eta data for differential cross sections and polarizations. We compare our results with present information on the two-photon eta-decay from the literature. We provide predictions for future PrimEx experiments at Jefferson Laboratory in order to motivate further studies.Comment: 5 pages, 6 figures, gamma-gamma*-eta form factor included, version to appear in Eur. Phys. J. A

    Measurement of ϕ\phi(1020) meson leptonic width with CMD-2 detector at VEPP-2M Collider

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    The ϕ\phi(1020) meson leptonic width has been determined from the combined analysis of 4 major decay modes of the resonance (ϕK+K,KL0KS0,π+ππ0,ηγ\phi\to K^+ K^-,K^0_LK^0_S,\pi^+\pi^-\pi^0,\eta\gamma) studied with the CMD-2 detector at the VEPP-2M e+ee^+e^- collider. The following value has been obtained: Γ(ϕe+e)=1.235±0.006±0.022\Gamma(\phi\to e^+e^-) = 1.235\pm 0.006\pm 0.022 keV. The ϕ(1020)\phi(1020) meson parameters in four main decay channels have been also recalculated: B(ϕK+K)=0.493±0.003±0.007B(\phi\to K^+K^-) = 0.493\pm 0.003\pm 0.007, B(ϕKLKS)=0.336±0.002±0.006B(\phi\to K_LK_S) = 0.336\pm 0.002\pm 0.006, B(ϕπ+ππ0)=0.155±0.002±0.005B(\phi\to\pi^+\pi^-\pi^0) = 0.155\pm 0.002\pm 0.005, B(ϕηγ)=0.0138±0.0002±0.0002B(\phi\to\eta\gamma) = 0.0138\pm 0.0002\pm 0.0002.Comment: 14 pages, 3 figure

    New precision measurement of the J/ψJ/\psi- and ψ\psi' -meson masses

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    A new high precision measurement of the J/ψJ/\psi- and ψ\psi'-meson masses has been performed at the VEPP-4M collider using the KEDR detector. The resonant depolarization method has been employed for the absolute calibration of the beam energy. The following mass values have been obtained: MJ/ψ=3096.917±0.010±0.007M_{J/\psi} = 3096.917 \pm 0.010 \pm 0.007 MeV, Mψ=3686.111±0.025±0.009M_{\psi'} = 3686.111 \pm 0.025 \pm 0.009 MeV. The relative measurement accuracy has reached 4.1064. 10^{-6} for J/ψJ/\psi and 7.1067. 10^{-6} for ψ\psi', approximately 3 times better than in the previous precise experiments.Comment: 12 pages, 4 tables, 10 figure

    New precise determination of the \tau lepton mass at KEDR detector

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    The status of the experiment on the precise τ\tau lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ+τ\tau^+\tau^- cross section behaviour around the production threshold. The preliminary result based on 6.7 pb1^{-1} of data is mτ=1776.800.23+0.25±0.15m_{\tau}=1776.80^{+0.25}_{-0.23} \pm 0.15 MeV. Using 0.8 pb1^{-1} of data collected at the ψ\psi' peak the preliminary result is also obtained: ΓeeBττ(ψ)=7.2±2.1\Gamma_{ee}B_{\tau\tau}(\psi') = 7.2 \pm 2.1 eV.Comment: 6 pages, 8 figures; The 9th International Workshop on Tau-Lepton Physics, Tau0

    Measurement of main parameters of the \psi(2S) resonance

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    A high-precision determination of the main parameters of the \psi(2S) resonance has been performed with the KEDR detector at the VEPP-4M e^{+}e^{-} collider in three scans of the \psi(2S) -- \psi(3770) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the \psi(2S) we obtained the mass value M = 3686.114 +- 0.007 +- 0.011 ^{+0.002}_{-0.012} MeV and the product of the electron partial width by the branching fraction into hadrons \Gamma_{ee}*B_{h} = 2.233 +- 0.015 +- 0.037 +- 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference effects in the cross section of the single-photon e^{+}e^{-} annihilation to hadrons explicitly considered in this work. Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the \psi(2S): \Gamma_{ee} =2.282 +- 0.015 +- 0.038 +- 0.021 keV, \Gamma = 296 +- 2 +- 8 +- 3 keV. These results are consistent with and more than two times more precise than any of the previous experiments
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