Density distributions of11Li deduced from reaction cross-section measurements

Abstract

We measured the reaction cross sections of the two-neutron halo nucleus ${}^{11}$Li with solid hydrogen and carbon targets at around 31 and 41 MeV/nucleon. The neutron density distribution of ${}^{11}$Li was deduced for the first time by the Glauber model calculation based on the optical limit approximation. The uncertainty of the matter density of ${}^{11}$Li was improved, compared with earlier measurements. The present root-mean-square radius of the proton distribution agrees with the previous one derived from an optical isotope shift measurement. The present root-mean-square radii reproduce theoretical calculations by the tensor optimized shell model by assuming core excitation. This consistency suggests the possibility that ${}^{9}$Li in ${}^{11}$Li is excited and the disappearance of the $N=8$ shell gap of ${}^{11}$Li is caused by correlations originating from the nucleon force, such as the tensor and the pairing.