Corrections to the Quasi-Free Process
At intermediate energy the photon-nucleus interaction is dominated by the quasi-free process: the photon interacts with one nucleon moving in a mean potential. The other nucleons are spectator in the sense that their overall effect is to create a mean optical potential in which the outgoing particles move (Distorted Wave Impulse Approximation).
The A(γ,π)B reactions induced by a monochromatic photon beam. Here the spectrum of pions emitted at a given angle is measured.
The A(γ,pπ)B reactions induced by a bremsstrahlung beam. Here the proton and the pion are detected in coincidence.
The dominance of this mechanism decreases quickly when the momentum of the spectator system increases, and strong deviations appear. They are understood in terms of the onset of two nucleon mechanisms. Two of them are of dominating importance: the Δ-N interaction and the meson exchange corrections to the γN → Nπ vertex. We shall put the emphasis on their consequences on the yield of pion photoproduction reactions induced on few body systems.
KeywordsPion Exchange Born Term Pion Photoproduction High Energy Part Relative Kinetic Energy
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