摘要
We re-study nucleon pole contribution in J/ψ → NN^-π decays by including the imaginary part for the propagator of the off-shell nucleon with energy above π N threshold. It is found that when including the imaginary part in the propagator, the branching ratio of the decay width will descend about 11% compared with the result without including the imaginary part, no matter whether including the off-shell form factors or not. It also leads to a phase of up to 25° for the off-shell nucleon propagator at invariant mass around 1400 MeV. This effect needs to be considered for detailed partial wave analysis of N^＊ resonances around this mass region.
基金
The project partly supported by National Natural Science Foundation of China under Grant Nos. 10475089, 10435080, 10447002, 10147202, and 10225525, the Physical Science Fund of Guangxi Province under Grant No. 9714005, and the Knowledge Innovation Key Project of the Chinese Academy of Sciences under Grant No. KJCX2-SW-N02.
