Scalar meson masses and mixing angle in a U(3)XU(3) Linear Sigma Model

Abstract

Meson properties are considered within a U(3)× U(3) Linear Sigma Model(LSM). The importance of the U_A(1)-breaking term and the OZI rule violating term in the generation of meson masses and mixing angles is stressed. The LSM parameters are fitted to the pseudoscalar meson spectrum thus giving predictions for scalar meson properties. The model predicts a scalar meson nonet whose members are: σ(≈ 400), f₀(980), κ(≈ 900) and a₀(980) resonances. Scalar meson mixing angle (in the |ns>, |s> basis) is predicted to be φ_S≈ -14^∘. Therefore the f₀(980) is predominantly strange while the σ(≈ 400) is mostly non-strange. The model also gives a pseudoscalar mixing angle φ_P≈ 35^∘ which corresponds to θ_P ≈ -19^∘ in the singlet-octet basis. Comparison with chiral perturbation theory shows that L₈ is saturated by scalar mesons exchange. However, LSM predicts that L₅ is not saturated by scalar mesons exchange as assumed in the literature.