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在对于质子上的π+光生过程作了一般考虑以后,我们从Mandelstam表示出发,进而采用Cini-Fubini近似,导出了关于π光生幅的同位标部分的公式。按照核子电磁结构的新数据,我们选取π-π作用的I=J=l共振的参数为tr=22,αv=1.52,bv=1.60,计算了(dσ)/(dΩ)(90°),(dσ‖)/(dσ⊥)(90°)以及三个能量下的角分布。结果表明,在加入π-π作用之后,与实验之间的调合比之Chew等的结果有很大的改进,所定出的γ+π→π+π的耦合常数约为∧≈-2.8e,这与时行的结果大致相符。After a general consideration for the process of π+-photoproduction from proton, starting from the Mandelstam representation and using further the Cini-Fubini approximation, we derive the formulas for the isoscalar part of π-photoproduction amplitudes. According to new data on electromagnetic structure of nucleon, we choose the parameters of I=I=1 resonance of π-π interaction to be tr = 22, av= 1.52, bv= 1.60, and calculate (dσ)/(dΩ)(90°),(dσ‖)/(dσ⊥)(90°) and angular distributions at three energies. The results show that after introducing the π-π interaction the fit to the experiment is much improved over the results obtained by Chew et al. The coupling constant of γ+π→π + π is determined to be about ∧≈- 2.8 e, which is roughly consistent with the current results.
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