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Register a new userFirst measurement of coherent double neutral-pion photoproduction on the deuteron at incident energies below 0.9 GeV
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The total cross sections were measured for coherent double neutral-pion photoproduction on the deuteron at incident energies below 0.9 GeV for the first time. No clear resonance-like behavior is observed in the excitation function for $W_{gamma d}=2.38$--2.61 GeV, where the $d^*(2380)$ dibaryon resonance observed at COSY is expected to appear. The measured excitation function is consistent with the existing theoretical calculation for this reaction. The upper limit of the total cross section is found to be $0.034$~$mu$b for the dibaryon resonance at $W_{gamma d}=2.37$~GeV (90% confidence level) in the $gamma d to pi^0pi^0 d$ reaction.
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The cross section and decay angular distributions for the coherent phi meson photoproduction on the deuteron have been measured for the first time up to a squared four-momentum transfer t =(p_{gamma}-p_{phi})^2 =-2 GeV^2/c^2, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cross sections are compared with predictions from a re-scattering model. In a framework of vector meson dominance, the data are consistent with the total phi-N cross section sigma_{phi N} at about 10 mb. If vector meson dominance is violated, a larger sigma_{phi N} is possible by introducing larger t-slope for the phi N to phi N process than that for the gamma N to phi N process. The decay angular distributions of the phi are consistent with helicity conservation.
Differential cross sections for the process pi^- p -> gamma n have been measured at Brookhaven National Laboratorys Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations. A new three-parameter SAID fit yields 36 +/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.
Neutral kaon photoproduction on the deuteron has been investigated by including the final state effects and compared with the experimental data. Comparison shows that the models used in this calculation can reproduce the data in the $Sigma$ channel regions fairly well but still give over predictions in the $Lambda$ channel. It seems that the tensor target asymmetries are more suitable for studying the final state effects. The extractions of the elementary photoproduction amplitude are also demonstrated.
This paper reports on a measurement of the double-polarization observable G in $pi^0$ photoproduction off the proton using the CBELSA/TAPS experiment at the ELSA accelerator in Bonn. The observable G is determined from reactions of linearly-polarized photons with longitudinally-polarized protons. The polarized photons are produced by bremsstrahlung off a properly oriented diamond radiator. A frozen spin butanol target provides the polarized protons. The data cover the photon energy range from 617 to 1325 MeV and a wide angular range. The experimental results for G are compared to predictions by the Bonn-Gatchina (BnGa), Julich-Bonn (JuBo), MAID and SAID partial wave analyses. Implications of the new data for the pion photoproduction multipoles are discussed.
The SciBooNE Collaboration reports a measurement of neutral current coherent neutral pion production on carbon by a muon neutrino beam with average energy 0.8 GeV. The separation of coherent from inclusive neutral pion production has been improved by detecting recoil protons from resonant neutral pion production. We measure the ratio of the neutral current coherent neutral pion production to total charged current cross sections to be (1.16 +/- 0.24) x 10-2. The ratio of charged current coherent pion to neutral current coherent pion production is calculated to be 0.14+0.30 -0.28, using our published charged current coherent pion measurement.
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