Magnetic and Axial-Vector Transitions of the Baryon Antidecuplet(Pentaquarks and related topics, Exotic hadrons, New Frontiers in QCD-Exotic Hadrons and Hadronic Matter-)

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We report the recent results of the magnetic transitions and axial-vector transitions of the baryon antidecuplet within the framework of the chiral quark-soliton model. The dynamical model parameters are fixed by experimental data for the magnetic moments of the baryon octet, for the hyperon semileptonic decay constants, and for the singlet axial-vector constant. The transition magnetic moments μΛΣ and μNΔ are well reproduced and other octet-decuplet and octet-antidecuplet transitions are predicted. In particular, the present calculation of μΣΣ* is found to be below the upper bound 0.82μN that the SELEX collaboration measured very recently. The results explains consistently the recent findings of a new N^* resonance from the GRAAL and Tohoku LNS group. We also obtain the transition axial-vector constants for the Θ^+→KN from which the decay width of the Θ^+ pentaquark baryon is determined as a function of the pion-nucleon sigma term ΣπN. We investigate the dependence of the decay width of the Θ^+ on the g^<(0)>_A, with the g^<(0)>_A varied within the range of the experimental uncertainty. We show that a small decay width of the Θ^+→KN, i.e. Γ_<ΘKN≤1 MeV, is compatible with the values of all known semileptonic decays with the generally accepted value of gA^^<(0)>≈0.3 for the proton.
理論物理学刊行会の論文
2007-11-09