Distinction between Proton-Neutron Density Distribution of Halo Nuclei at the Nuclear Surface via Reaction Cross Sections

Reaction cross sections (σ_R) for ¹¹Be and ⁸B on proton targets at 50 A ∼ 120 A MeV have been measured to distinguish between the proton- and neutron- density distributions at the nuclear surface. The σ_R is connected with the nucleon density distributions by the Glauber theory. Since the nucleon-nucleon total cross sections in that energy region have a large isospin dependence, the σ_R on proton targets should have a large difference between the proton and neutron in the halo structure. The experimental σ_R on proton targets are in good agreement with the calculated ones assuming that the tail dominantly consists of a neutron for ¹¹Be and a proton for ⁸B.