Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
; CCAST, World Lab, Beijing 100080, Peoples R China
; Chinese Acad Sci, Inst Theoret Phys, Beijing 100080, Peoples R China
; Natl Lab Heavy Ion Accelerator, Ctr Theoret Nucl Phys, Lanzhou 730000, Peoples R China
For the N (N) over bar system, the one-pion-exchange (OPE) interaction gives the largest attractive force for N (N) over bar with an isospin I=0 and spin S=0, while a near-threshold enhancement was observed for p (p) over bar with I=0 and S=0 in J/psi-->gammapp $$($) over bar decays. With a K-matrix approach, we find that the OPE final-state interaction makes an important contribution to the near-threshold enhancement in the p (p) over bar mass spectrum in J/psi-->gammap (p) over bar decays.