Proton elastic scattering at 200 A MeV and high momentum transfers of 1.7–2.7 fm$^{−1}$ as a probe of the nuclear matter density of $^6$He

Differential cross sections of p-He-6 elastic scattering were measured in inverse kinematics at an incident energy of 200 AMeV, covering the high momentum transfer region of 1.7-2.7 fm(-1). The sensitivity of the elastic scattering at lowand high momentum transfers to the density distribution was investigated quantitatively using relativistic impulse approximation calculations. In the high momentum transfer region, where the present data were taken, the differential cross section has an order of magnitude higher sensitivity to the inner part of the He-6 density relative to the peripheral part (15:1). This feature makes the obtained data valuable for the deduction of the inner part of the He-6 density. The data were compared to a set of calculations assuming different proton and neutron density profiles of He-6. The data are well reproduced by the calculation assuming almost the same profiles of proton and neutron densities around the center of He-6, and a proton profile reproducing the known point-proton radius of 1.94 fm. This finding is consistent with the assumption that the He-6 nucleus consists of a rigid alpha-like core with a two-neutron halo.