Masses and Widths of Light Scalar Mesons in Chiral Perturbation Theory

Abstract

Based on the diquark model, we assume that the light scalar mesons are q2q̄2 states rather than qq̄. The chiral effective Lagrangian for the light scalar meson is constructed, and the mass relations are obtained: the isotriplet (a0) and the isosinglet (f0) are the heaviest and are degenerate, the isodoublets (κ) are heavier and the other isosinglet (σ) is the lightest; and 2Mκ2= Ma02 + Mσ2. Using experimental value for a0 and σ mass, we obtain Mκ = 794 MeV, which is consistent with the experimental value. Then taking Γ(a00 → ηπ0) = 90 MeV and Γ(f00 → π0π0) = 20 MeV, we get the width of σ is: Γ(σ → π+π−) = 150 MeV.

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