No abstract available

[en] The high quality of the tagged photon beam of the MAMI accelerator in Mainz (Germany) coupled with the large acceptance tracking detector DAPHNE, allowed for the first time high precision measurements of N-body final state interactions ³He(γ,pd) and ³He(γ,ppn)

[en] Short communication

[en] A large-acceptance (94% of 4π sr) hadron detector capable of handling multiparticle final states is described. The track reconstruction capability, energy resolution, particle identification capability and neutral-particle detection efficiency of the detector are discussed and the results of tests shown. Tests have been performed both with cosmic rays and in a realistic experimental situation using a 500 MeV photon beam impinging on hydrogen and deuteron targets. (orig.)

[en] The small electric quadrupole E2 amplitude of the predominantly magnetic dipole M1 p→Δ(1232) transition has been measured using 270 to 420MeV tagged linearly polarized photons in the p(γ searrow,p)π^o reaction at the Mainz Microtron MAMI. Differential cross sections and photon asymmetries were determined by measuring the recoil proton in the cylindrically symmetric 4π detector DAPHNE. From the proton angular distributions the ratio E2/M1=-(2.5±0.2±0.2)% at the maximum of the Δ(1232) resonance has been derived. copyright 1997 The American Physical Society

[en] The total and the differential cross sections for the D(γ,p)n reaction have been measured over the photon energy range 100-800 MeV at the 855 MeV MAMI Microtron in Mainz. Using the large acceptance detector DAPHNE in conjunction with the Glasgow tagging spectrometer, high precision results with small systematic errors were obtained. The data are presented in the form of thirty-five angular distributions at c.m. proton angles between 30 ^circle -160 ^circle in 10 ^circle intervals and at photon energies in steps of 20 MeV. Previous experimental work is reassessed in the light of the present results and comparison with some recent theoretical calculations. (orig.)

[en] The total cross section for the γn→pπ^-π⁰ reaction has been measured over the photon energy range 450 endash 800 MeV at the 855 MeV MAMI Microtron in Mainz with the large acceptance detector DAPHNE and using a deuterium target. As expected, this reaction has a very similar cross section to the γp→nπ⁺π⁰ channel and its amplitude is strongly underestimated by the existing double pion photoproduction models. copyright 1997 The American Physical Society

[en] The total photoabsorption cross section for ⁴He has been measured for the first time over a wide photon energy range (200 MeV≤E_γ≤800 MeV). By using the large acceptance detector DAPHNE at the tagged photon facility of the MAMI microtron in Mainz high precision results with small systematic errors were obtained. This measurement shows that ⁴He has a behavior similar to heavy nuclei and, in particular, a reduction of the cross section with respect to the lighter nuclei is found for E_γ>600 MeV. copyright 1997 The American Physical Society

[en] The total photoabsorption cross sections for ¹H, ²H, and ³He have been measured for incident photon energies ranging from 200 to 800 MeV. The ³He data are the first for this nucleus. By using the large acceptance detector DAPHNE in conjunction with the tagged photon beam facility of the MAMI accelerator in Mainz, cross sections of high precision have been obtained. The results show clearly the changes in the nucleon resonances in going from ¹H to ³He. In particular, for the D₁₃ region the behavior for ³He is intermediate between that for ¹H, ²H, and heavier nuclei. This will provide a strong constraint to the theories that are presently being developed with a view to explaining the apparent open-quote open-quote damping close-quote close-quote of higher resonances in heavy nuclei. copyright 1996 The American Physical Society

[en] The cross section of the ³He (γ,pp)n reaction has been measured for the first time over a wide photon energy and proton angular range (200 MeV ≤ Eγ ≤ 800 MeV; 20 deg ≤ v^lab_p ≤ 160 deg) using the large acceptance detector DAPHNE at the tagged photon facility of the microtron in Mainz. The wide kinematical coverage of the measurement has allowed a detailed analysis of three nucleon absorption mechanisms. A model developed by Laget explains the main characteristics of the data in the Δ resonance region. (authors)