Uₐ(1) Breaking Effects on the Light Scalar Meson Spectrum

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Effects of the Uₐ(1) breaking interaction on the low-lying nonet scalar mesons are studied using the extended Nambu-Jona-Lasinio model. The strength of the Uₐ(1) breaking interaction is determined by the electromagnetic decays of the eta meson. We find that the Uₐ(1) breaking interaction gives rise to about 150 MeV mass difference between the sigma and a₀ mesons. We also find that the strangeness content in the σmeson is about 15%. The calculated mass of the I=1/2 state is about 200 MeV heavier than that of the I=1 state. The order of these masses is not likely to change within this model.