A Phenomenological Analysis of Single Pion Photoproduction in the First Resonance Region

概要

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Single pion photoproduction in the first resonance region is investigated on the basis of noe-particle-exchange model. In addition to the Born terms, s-, t- and u-channel exchanges of N_<11>, Δ_<33>, N_<13>, ρ and ω are taken into consideration. In order to guarantee the unitarity we use the K-matrix method. The coupling constants and off-mass-shell parameters are determined by χ^2-fit. The coupling constants obtained are consistent with the values estimated by the use of the radiative decay widths and the results of low energy pion-nucleon or nucleon-nucleon analyses. Our predicted multipoles are in fairly good agreement with the experiments. Δ_<33> contribution is dominant to M_<1+>^<(3/2)>. and is very small to E_<1+>^<(3/2)>. The main contribution to E_<1+>^<(3/2)> is due to the Born terms and the double zero observed in this multipole is well reproduced by incorporating unitarity. ρ exchange is positively required multipole is well reproduced by incorporating unitarity. ρ exchange is positively required to explain the absolute value and energy dependence of _nM_<1->^<(1/2)>. It was argued that this structure will show the onset of N_<11> resonance. However, its contribution is too small to support this argument.
理論物理学刊行会の論文
1978-06-25