The Meson-Baryon Chiral Effctive Lagrangian

Chiral perturbation theory is designed to describ the low energy hadron physics by the chiral symmetry from taking the light quark mass to zero. The first step in the chiral perturbation theory is to get the chiral lagrangian. The lower order effective lagrangian of pseudoscalar mesons and baryons already has been constructed. The pseudoscalar mesons lagrangian has been constructed to order six, the meson-nucleon lagrangian has been constructed to order four now. The meson-baryon lagrangian of considering three-flavor quarks were obtained third-order.The meson lagrangian has been constructed to the level of two-loop graphs. the meson-nucleon lagrangian also to one-loop graphs. however the one-loop graphs of the meson-baryon lagrangian have not been constructed completely. Our main job is to construct the fourth order meson-baryon effective lagrangian by considering a variety of constraints. Adopting a systematic approach and using symbolic computation method, We get the fourth meson-baryon lagrangian. We also tested the first three lagrangians of literature.Running coupling constant of the strong interaction had not been determined in the form of low-energy region. According to the relationship of low energy constants and low-energy running coupling constant, we explored three forms of low-energy running coupling constant and showed the effect of low-energy running coupling constant to low energy constants.