| Popis: |
For $^{4,6,8}$He, Tanihata et al. determined matter radii $r_{m}(\sigma_{\rm I})=1.57(4), 2.48(3), 2.52(3)$~fm from interaction cross sections $\sigma_{\rm I}$ for $^{4,6,8}$He scattering on Be, C Al targets at 790~MeV/nucleon. Lu et al. measured the atomic isotope shifts (AIS) for $^{4,6,8}$He and determined proton radii $r_{p}({\rm AIS})$ for $^{4,6,8}$He. As for p+$^{4,6,8}$He scattering, reaction cross sections $\sigma_{\rm R}({\rm exp})$ are available at 700~MeV with high accuracy. Our aim is to determine matter radii $r_{m}$ and skins $r_{\rm skin}$ for $^{6,8}$He from the $\sigma_{\rm R}({\rm exp})$ and the $r_{p}({\rm AIS})$. {\bf Method:} Our model is the Love-Franey $t$-matrix folding model, since the model is better than the optical limit of Glauber model. Our results for $^{6,8}$He are $r_{m}({\rm exp})=2.48(3), 2.53(2)$~fm and $r_{\rm skin}=$0.78(3), 0.82(2)~fm. For $^{6,8}$He, our results $r_{m}(\sigma_{\rm R})$ agree with those of Tanihata {\it et al.}. For $^{8}$He, the distance between $^{4}$He and the center of mass of valence four neutrons is 2.367~fm. |
