Photoemission of protons from4He in theΔ-resonance region

Wichmann, R.; Ahrens, J.; Arends, H. J.; Beck, R.; Galler, G.; Hünger, A.; Kraus, Alfred A.; MacGregor, I. J. D.; Peise, J.; Seitz, B.; Schmitz, M.; Schneider, M.; Selke, O.; Schumacher, M.; Wissmann, F.

doi:10.1007/bf02769681

Cited by 1 publication

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“…This bump-like structure occurs through excitation of the ∆ resonance with subsequent two-nucleon disintegration of the deuteron. In recent experimental investigations on 4 He [158] with the subsequent theoretical investigations [157] on complex nuclei it was shown that -after a ∆ excitation -there is a branching of strength into the non-mesonic channel and into the mesonic channel with a conservation of strength as compared to the free nucleon. This consideration shows that the resonance-like structure in the non-mesonic pn channel is not part of the QD degree of freedom but of the nucleon internal degrees of freedom which will be described by the amplitude T N .…”

Section: Further Properties Of Quasideuteronsmentioning

confidence: 99%

Compton scattering by nuclei

et al. 2000

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The concept of Compton scattering by even-even nuclei from giant-resonance to nucleon-resonance energies and the status of experimental and theoretical researches in this field are outlined. The description of Compton scattering by nuclei starts from different complementary approaches, namely from second-order S-matrix and from dispersion theories. Making use of these, it is possible to incorporate into the predicted nuclear scattering amplitudes all the information available from other channels, viz. photon-nucleon and photon-meson channels, and to efficiently make use of models of the nucleon, the nucleus and the nucleon-nucleon interaction. The total photoabsorption cross section constrains the nuclear scattering amplitude in the forward direction. The specific information obtained from Compton scattering therefore stems from the angular dependence of the nuclear scattering amplitude, providing detailed insight into the dynamics of the nuclear and nucleon degrees of freedom and into the interplay between them. Nuclear Compton scattering in the giant-resonance energy-region provides information on the dynamical properties of the in-medium mass of the nucleon. Most prominently, the electromagnetic polarizabilities of the nucleon in the nuclear medium can be extracted from nuclear Compton scattering data obtained in the quasideuteron energy-region. In our description of this latter process special emphasis is laid upon the exploration of many-body and two-body effects entering into the nuclear dynamics. Recent results are presented for two-body effects due to the mesonic seagull amplitude and due to the excitation of nucleon internal degrees of freedom accompanied by meson exchanges. Due to these studies the inmedium electromagnetic polarizabilities are by now well understood, whereas the understanding of nuclear Compton scattering in the ∆-resonance range is only at the beginning. Furthermore, phenomenological methods how to include retardation effects in the scattering amplitude are discussed and compared with model predictions.

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Section: Further Properties Of Quasideuteronsmentioning

confidence: 99%