Medium energy antiproton absorption, a tool to study neutron halo nuclei

Abstract

A novel method is proposed to measure the difference of neutron and proton density distributions of nuclei far off stability by medium energy antiproton absorption. The radioactive nuclei are produced by projectile fragmentation at medium energies (400–800) A MeV, separated and stored in a medium energy storage ring. The antiprotons are produced with 30 GeV protons, accumulated, cooled, decelerated and stored at energies of about 5 MeV in a small storage ring. The medium energy radioactive beams are brought to head on collisions with the low energy antiproton beam in an interaction section of both rings. The coasting radioactive beam and the reaction products from the collisions with the antiprotons are observed with the Schottky noise frequency analysis method, which allows one to separate all reaction products and measure their production rates as well as the loss rate of the primary beam. From these observations, the total and partial reaction cross sections may be determined, even with a small number of rare ion species in the ring. An analysis of the total and partial reaction cross sections will allow to determine both 〈 r p 2〉 as well as 〈 r n 2〉 for nuclei far off the stability.