2,212 research outputs found

    η\eta-Meson Decays and Strong UA(1)U_A(1) Breaking in the Three-Flavor Nambu-Jona-Lasinio Model

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    We study the ηγγ\eta \to \gamma \gamma and ηπ0γγ\eta \to \pi^0 \gamma \gamma decays using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. We find that the η\eta-meson mass, the ηγγ\eta \to \gamma \gamma decay width and the ηπ0γγ\eta \to \pi^0 \gamma \gamma decay width are in good agreement with the experimental values when the UA(1)U_{A}(1) breaking is strong and the flavor SU(3)SU(3) singlet-octet mixing angle θ\theta is about zero. The effects of the UA(1)U_A(1) breaking on the baryon number one and two systems are also studied.Comment: 12 pages, LaTeX, 2 eps figures, Talk given at the Joint Japan-Australia Workshop on Quarks, Hadrons and Nuclei, Adelaide, Australia, Nov. 15-24, 199

    SU(3) lattice QCD study for octet and decuplet baryon spectra

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    The spectra of octet and decuplet baryons are studied using SU(3) lattice QCD at the quenched level. As an implementation to reduce the statistical fluctuation, we employ the anisotropic lattice with O(a)O(a) improved quark action. In relation to Λ(1405)\Lambda(1405), we measure also the mass of the SU(3) flavor-singlet negative-parity baryon, which is described as a three quark state in the quenched lattice QCD, and its lowest mass is measured about 1.6 GeV. Since the experimentally observed negative-parity baryon Λ(1405)\Lambda(1405) is much lighter than 1.6 GeV, Λ(1405)\Lambda(1405) may include a large component of a NKˉN \bar K bound state rather than the three quark state. The mass splitting between the octet and the decuplet baryons are also discussed in terms of the current quark mass.Comment: 8 pages, 3 figures, proceeding of "International Symposium on Hadron and Nuclei" at Yonsei Univ., Seoul, Korea 20-22 Feb. 200

    Precursor of Color Superconductivity in Hot Quark Matter

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    We investigate possible precursory phenomena of color superconductivity in quark matter at finite temperature T with use of a simple Nambu-Jona-Lasinio model. It is found that the fluctuating pair field exists with a prominent strength even well above the critical temperature T_c. We show that the collective pair field has a complex energy located in the second Riemann sheet, which approaches the origin as T is lowered to T_c. We discuss the possible relevance of the precursor to the observables to be detected in heavy ion collisions.Comment: 5 pages, 3 figures, version to appear in Phys. Rev. D. Discussions are enlarged on the physical origin of the large fluctuation of the pair field and its phenomenological consequences. References are adde