Analysis on the composite nature of exotic state and its effective range expansion

The proportion of internal components of hadrons is discussed by the composite coefficient method, and the results show that the composite coefficients of the resonance can quantitatively describe the internal structure of some exotic hadron states．Three different methods were determined, namely, the relationship between the total width and the composite coefficient, the theoretical method of Flatté parameterization, and the spectral function of the near-threshold resonance．Combining effective range expansion and Flatté parameterization, the scattering length and effective range related to the exotic resonance are discussed, and the corresponding calculation and discussion are carried out by taking the light scalar meson f₀ (980) as an example．