Possibility of a ninthJP=12+baryon

It is shown that (i) the small but definite discrepancy between the mass-squared Gell-Mann-Okubo mass formula of the ${\frac{1}{2}}^{+}$ baryons and experiment, (ii) the trouble of the $\Sigma -\Lambda$ degeneracy, and (iii) the deviation of the $\frac{D}{F}$ ratio of the axial-vector semileptonic couplings from the SU(6) value as indicated by the value $\left|\frac{G_A}{G_V}\right|=0.435\mathrm{}\pm 0.035$ of the latest high-statistics experiment on the ${\Sigma }^{-}\to n+e^{-}+\overline{\nu }$ decay as compared with the SU(6) value ≃ 0.25, can be explained simultaneously if a ninth $I=0,{\frac{1}{2}}^{+}$ baryon ${\Lambda }^{\prime }$ exists around 1700 MeV with a broad width of about 1 GeV. The hyperon semileptonic decays in the presence of the ${\Lambda }^{\prime }$ are analyzed in detail. The Cabibbo angles are determined to be $sin{\theta }_V=0.227\mathrm{}\pm 0.008$ and $sin{\theta }_A=0.220\mathrm{}\pm 0.020$. The theoretical frameworks used are asymptotic SU(3), chiral $\mathrm{SU}\mathrm{}\left(3\right)\mathrm{}\otimes \mathrm{SU}\mathrm{}\left(3\right)\mathrm{}$ charge algebra, and the simple mechanism of symmetry breaking.