793 research outputs found

    Recent results from e+ e- --> hadrons

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    New results on the low energy e+ e- annihilation into hadrons from Novosibirsk and Beijing are described. Implications of the new measurements for the evaluation of the hadronic contribution to the muon anomalous magnetic moment are discussed.Comment: Invited talk at the Seventh International Workshop on Tau Lepton Physics (TAU02), Santa Cruz, Ca, USA, Sept 2002, 7 pages, 4 figure

    Pion Form Factor Phase, PIon Pion Elasticity and New Electron-Positron Data

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    New precise data on the low energy electron-positron annihilation into hadrons from Novosibirsk are used to obtain bounds on the elasticity parameter and the difference between the phase of the pion form factor and that of pion pion scatteringComment: 9 pages, 4 figures, submitted to Physics Letters

    Four-pion production

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    Starting from the low-energy structure derived from QCD, we extend the amplitudes for four-pion production in e+ e- annihilation and tau decays up to invariant four-pion masses of 1 GeV. Cross sections and branching ratios BR(rho^0 -> 4 pi) are compared with available data.Comment: 4 pages, 3 figures, contribution to Proc. of QCD'02, Montpellier, July 2002, misprints correcte

    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
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