Elastic proton scattering from neutron-rich He-isotopes at intermediate energies and high momentum transfer

Abstract

Neutron-rich light nuclei near the neutron drip line have attracted much attention in recent years as they feature a particular nuclear structure, namely an extended distribution (so-called halo) of the valence neutrons surrounding a compact nuclear core. Elastic proton scattering is known as a suitable technique for exploring the nuclear matter distributions in the stable nuclei. It was successfully employed at GSI also for the radioactive nuclei 6,8He and 8,9,11Li [1–3]. The experimental technique of inverse kinematics was applied using radioactive beams with energies near 700 MeV/u. The elastic differential cross section for small-angle scattering (3° ≤ θCM ≤ 10°) was deduced from the data taken with the ionization chamber IKAR, as an active target, and a forward spectrometer. The method has been demonstrated to be very effective for obtaining valuable information on the nuclear matter distribution in the halo nuclei under investigation, such as 6He, 8He and 11Li. The previous measurements at small momentum transfer have been highly sensitive on the nuclear sizes and the radial distributions of the nuclear matter density. Recently, a novel experimental approach has been accomplished with the aim to deduce the differential p6,8He cross sections for larger angles (10≤ ± θCM ≤ 30°) that correspond to a higher momentum transfer which covers the region of the first diffraction minimum.