; Zhang, Yuan-Jiang
; Zhao, Qiang] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Zhao, Qiang] CAS, Theoret Phys Ctr Sci Facil, Beijing 100049, Peoples R China
In the J/psi radiative decay channels J/psi -> gamma V (V) over bar, the result of partial wave analysis indicates that the V (V) over bar systems are predominately pseudoscalar component, and most of these channels have relatively large branching ratios at an order of 10(-3). Meanwhile, vector mesons, such as rho, omega, and K*, have strong couplings with nucleons and/or hyperons. This suggests a dynamical mechanism describing the eta p (p) over bar form factors for higher eta mesons, such as eta(1405/1475) and eta(1760). It is thus natural to expect that rescatterings of these vector meson pairs into p (p) over bar of 0(-) partial wave could be an important source contributing to J/psi -> gamma p (p) over bar of which the branching ratio is at the order of 10(-4). Our calculation justifies this point. In particular, we find that interferences between different rescattering amplitudes can produce a significant threshold enhancement in the invariant mass spectrum of p (p) over bar. Without introducing dramatic ingredients, our model provides a natural explanation for the peculiar threshold enhancement observed by BES-II in J/psi -> gamma p (p) over bar. Additional experimental constraints on the V (V) over bar -> p (p) over bar transitions are examined. This mechanism in J/psi -> omega p (p) over bar is also discussed.