Resonance Effective Theory And Its Study Of η’â†'ηππ

Chiral Perturbation Theory is the low energy effective theory of QCD. It is based on the simultaneous expansion on the light-quark masses, the Goldstone-boson momentum squared and 1/NC. The results from Chirality Perturbation Theory automatically meet the requirements of the global symmetry of QCD, which makes Chiral Perturbation Theory become a reliable tool to describe the strong interaction in the low energy region. When the energy of a process is around the resonance mass, the perturbative expansion of Chirality Perturbation Theory is no longer valid. In this case, the effects of resonance must be taken into account explicitly. Resonance Chiral Theory is then proposed and it can describe the interactions between resonances and the Goldstone bosons.In this thesis, we study the hadronic decays η’ â†'ηππ within the framework of Resonance Chiral Theory. The contributions from leading order, scalar resonance exchange, tensor resonance exchange and the loop diagrams are calculated. We also briefly discuss the η-η mixing,the masses of η and η and the decay constants of Ï€ and K. We take the final state interactions ofππ into account by using the method of N/D unitarization and calculate the position of σ pole.We then study the Dalitz parameters and Dalitz plots both in the perturbative and unitarized approaches. The position of σ pole is close to the value given in PDG. The tensor resonance shows some relevance in determining the Dalitz parameters. The ππ loop diagrams play an important role in those Dalitz parameters.