; Zhang Yin-Jie
; Zou Bing-Song] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Wu Feng-Quan] Chinese Acad Sci, Natl Astron Observ, Beijing 100012, Peoples R China
; [Zou Bing-Song] Chinese Acad Sci, Theoret Phys Ctr Sci Facil, Beijing 100049, Peoples R China
; [Zhang Yin-Jie] Hebei Univ, Coll Phys Sci & Technol, Baoding 071002, Peoples R China
The low-energy S-wave pi N and KN scatterings are studied by using the K-matrix approach within the meson exchange framework. The t-channel meson exchanges, especially p and a exchanges, are found to play a very important role in these two processes. The t-channel p exchange determines the isospin structure of the scattering amplitudes, it gives attractive force in the low isospin state but repulsive force in the high isospin state. The t-channel sigma exchange gives a very large contribution in these two processes, while it is negligible in meson-meson S-wave scatterings.