Magnetic and axial-vector transitions of the baryon antidecuplet

Abstract

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 $μ_{ΛΣ}$ and $μ_{NΔ}$ are well reproduced and other octet-decuplet and octet-antidecuplet transitions are predicted. In particular, the present calculation of $μ_{ΣΣ^*}$ is found to be below the upper bound $0.82μ_N$ 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 $Θ^+\to KN$ from which the decay width of the $Θ^{+}$ pentaquark baryon is determined as a function of the pion-nucleon sigma term $Σ_{πN}$. We investigate the dependence of the decay width of the $Θ^{+}$ on the $g_{A}^{(0)}$, with the $g_{A}^{(0)}$ varied within the range of the experimental uncertainty. We show that a small decay width of the $Θ^{+}\to KN$, i.e. $Γ_{ΘKN} \leq 1$ MeV, is compatible with the values of all known semileptonic decays with the generally accepted value of $g_{A}^{(0)} \approx 0.3$ for the proton.