Effect ofΛNTensor Force onHeΛ5

The effect of a tensor component in the $\Lambda N$ force on the binding $B_{\Lambda }$ of a $\Lambda$ particle in ${}_{\Lambda }{}^{}{}_{}{}^5\mathrm{He}$ is investigated using the Hartree-Fock and rigid-$\alpha$ models. Second-order effects of the $\Lambda N$ tensor force are taken into account in an approximate way. With a variety of $\Lambda N$ noncentral forces that fit the low-energy $\Lambda p$ scattering data, overbinding of ${}_{\Lambda }{}^{}{}_{}{}^5\mathrm{He}$ persists. For $B_{\Lambda }$ calculations in this hypernucleus, the rigid-$\alpha$ model is found to be as good as the more elaborate Hartree-Fock scheme.