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The cross section of the $e^+e^-\to\omega\pi^0\to\pi^0\pi^0\gamma$ reaction was measured by the SND detector at VEPP-2M $e^+e^-$ collider in the energy range from threshold up to 1.4 GeV. Results of the cross section fitting by the sum of $\rho$, $\rho^{\prime}$ and $\rho^{\prime\prime}$ contributions are presented.
Only statistical errors are presented.
Results of systematic measurements of the asymmetry parameter in the elastic scattering of pions on polarized protons at 1.4–2.1 GeV/ c in the backward hemisphere are presented together with a test of the isospin invariance of the data set available on pion-proton scattering in the investigated momentum range. The transversity isodoublet amplitudes at 1.98 and 2.07 GeV/ c are reconstructed. The obtained data, the isospin analysis and amplitude reconstruction results are compared with the current phase-shift analysis predictions.
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The complete results of the experiments carried out with the Neutral Detector at the e + e − storage ring VEPP-2M in the energy range 2 E =0.5–1.4 GeV are reviewed. The data sample corresponds to a total integrated luminosity of 19 pb −1 .
ND results from Dolinsky et al., PL B174 (1986) 453.. Statistical errors only are shown. There is an additional systematic errorof 8%.
New ND data.. Statistical errors only are shown. There is an additional systematic errorof 8%.
Averaged ND data.. Statistical errors only are shown. There is an additional systematic errorof 8%.
The reaction e + e − → ηπ + π − has been studied with the Neutral Detector in the CM energy range 1.05–1.40 GeV at VEPP-2M. At the maximum energy the cross section exceeds the prediction of the vector dominance with one ϱ(770). The following upper limits for the electron width times branching ratio into ηπ + π − have been obtained for a resonance with a mass of 1.28 GeV and width of 0.08 GeV observed with the Omega-spectrometer at CERN: Λ ee · B ηππ < 9 eV, and for a ϱ′(1250) with a mass of 1.26 GeV and width of 0.125 GeV: Λ ee · B ηππ < 14 eV at 90% confidence level.
Axis error includes +- 10/10 contribution (RES-DEF(RES=ETA,DEF=530<M(2GAMMA)<570 MEV,BACK=CORRECTED)).
The reaction e + e - → ωπ 0 → π 0 π 0 γ has been studied with the Neutral Detector at the VEPP-2M collider. The cross section values differ from the predictions of the vector dominance model with one ϱ(770) meson, and are consistent with the contributions of ϱ(770) and ϱ(1600). ϱ(1250) has not been observed.
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The cross section of the reaction e + e − → K + K − has been measured at the electron-positron storage ring VEPP-2M in the c.m. energy range 1.0–1.4 GeV. At energies above 1.15 GeV the experimental values of the charged kaon form factor considerably exceed the predictions of the simplest vector dominance model with ϱ, ω, ψ mesons.
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Exclusive rho^+ rho^- production in two-photon collisions involving a single highly-virtual photon is studied with data collected at LEP at centre-of-mass energies 89 GeV < \sqrt{s} < 209 GeV with a total integrated luminosity of 854.7 pb^-1. The cross section of the process gamma gamma^* -> rho^+ rho^- is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 1.2 GeV^2 < Q^2 < 30 GeV^2 and 1.1 GeV < W_gg < 3 GeV. The \rho^+\rho^- production cross section is found to be of the same magnitude as the cross section of the process gamma gamma^* -> rho^0 rho^0, measured in the same kinematic region by L3, and to have similar W_gg and Q^2 dependences.
Cross sections for the reaction E+ E- --> E+ E- RHO+ RHO-. The differentialcross sections are corrected to the centre of each bin.
Cross sections for the two photon production of RHO+ RHO-.
Differential cross section for the process E+ E- --> E+ E- (RHO+ PI- PI0 + RHO+ RHO- PI0 PI0) corrected to bin centre.
The beam asymmetry, $\Sigma$, was measured at ELSA in the reaction $\vec \gamma p \to \eta p$ using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented to provide polarised photons in the energy range $E_\gamma = 800$ to 1400 MeV with the maximum polarisation of $P_\gamma = 49$ % obtained at 1305 MeV. Both dominant decay modes of the $\eta$ into two photons and $3\pi^0$ were used to extract the beam asymmetry from the azimuthal modulation of the cross section. The measurements cover the angular range $\Theta_\text{cm}\simeq 50$ -- 150 degrees. Large asymmetries up to 80 % are observed, in agreement with a previous measurement. The eta-MAID model and the Bonn--Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly.
Photon asymmetry for eta photoproduction at incident photon energy of 850 MeV.
Photon asymmetry for eta photoproduction at incident photon energy of 950 MeV.
Photon asymmetry for eta photoproduction at incident photon energy of 1050 MeV.
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