Study Of The Thermal Properties Of Light Scalar Resonances And The Structures Of The Exotic Hadrons

Chiral Perturbation Theory is a reliable tool to study the low energy dynamics of hadron interaction.Chiral Perturbation Theory is an important effective field theory.The degrees of freedom of chiral perturbation theory are not quarks and gluons,but the light pseudoscalar mesons.The main work of this paper is based on chiral perturbation theory.This paper contains two parts,which are summarized belowIn the first part,we study the thermal properties of the lowest multiplet of the quantum chromodynamics light-flavor scalar resonances,including the fo?500?/?,K0*?700?/?,f₀?980?and a₀?980?,in the framework of unitarized U?3?chiral perturbation theory.After the successful fits to the meson-meson scattering inputs,such as the phase shifts and inelasticities,we obtain the unknown parameters and further calculate the resonance poles and their residues at zero temperature.By including the finite-temperature effects in the unitarized meson-meson scattering amplitudes,the thermal behaviors of the scalar resonance poles in complex energy plane are studied.The masses of ? and ? are found to considerably decrease when increasing the temperatures,while their widths turn out to be still large when the temperatures reach around 200MeV.In contrast,both the masses and widths of the f₀?980?and a₀?980?are only slightly changedIn the second part,we study the resonances near the thresholds of the open heavy-flavor exotic hadrons using the effective-range expansion method.These exotic hadrons contain the Z_c?3900?,X?4020?,?c1?4140?,??4260?,and ??4660?,the scattering lengths and effective ranges from the masses and widths of resonances are determined.On this basis,quantitative discussions on the possible inner structures of the aforementioned resonances are given.