Nucleon pole contributions in $J/ψ\to N \bar{N} π$, $p \bar{p} η$, $p \bar{p} η^{\prime}$ and $p \bar{p} ω$ decays

Abstract

Nucleon pole contributions in $J/ψ\to N \bar N π$, $p \bar p η$, $p \bar p η^{\prime}$ and $p \bar{p} ω$ decays are re-studied. Different contributions due to PS-PS and PS-PV couplings in the $π$-N interaction and the effects of $NNπ$ form factors are investigated in the $J/ψ\to N \bar N π$ decay channel. It is found that when the ratio of $|F_0| /|F_M|$ takes small value, without considering the $NNπ$ form factor, the difference between PS-PS and PS-PV couplings are negligible. However, when the $NNπ$ form factor is included, this difference is greatly enlarged. The resultant decay widths are sensitive to the form factors. As a conclusion, the nucleon-pole contribution as a background is important in the $J/ψ\to N\bar{N}π$ decay and must be accounted. In the $J/ψ\to N\bar{N}η$ and $N\bar{N}η'$ decays, its contribution is less than 0.1% of the data. In the $J/ψ\to N\bar{N}ω$ decay, it provides rather important contribution without considering form factors. But the contribution is suppressed greatly when adding the off-shell form factors. Comparing these results with data would help us to select a proper form factor for such kind of decay.