Spin content of the $\Lambda$ hyperon

Abstract

Using the known experimental data for the hyperon semileptonic decay constants, we calculate integrated quark densities $\Delta q_\Lambda$ and $% \Delta \Sigma_\Lambda$ for the hyperon $\Lambda$ with flavor SU(3) symmetry breaking taken into account. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. This parametrization allows us to reproduce the first moment of the $g_1^{{\rm p}}(x)$ of the proton. For the $\Lambda$ we obtain: $\Delta u_{\Lambda}=\Delta d_{\Lambda} \approx 0$ and $\Delta s_{\Lambda}$ of the order of 1. Unfortunately large experimental errors of $\Xi^-$ decays propagate in our analysis especially in the case of $\Delta\Sigma_{\Lambda}$ and $\Delta s_{\Lambda}$. Only if the errors for these decays are reduced, the accurate theoretical predictions for $\Delta\Sigma_{\Lambda}$ and $% \Delta s_{\Lambda}$ will be possible.