Antiprotons and Nuclear Periphery

The peripheral neutron to proton density ratios determined using antiproton annihilations are compared with predictions of the semi-phenomenological model of Gambhir and Patil and with the HFB model. Reasonable agreement is obtained. The same data are also compared with experiments determining the difference between neutron and proton rms radii, Δr_np. It is shown that under the assumption of the peripheral densities given by 2pF distributions, the Δr_np values measured for neutron rich nuclei are due to the increase of the neutron diffuseness rather than to the increase of the neutron half-density radius.