INTERACTION CROSS-SECTIONS AND MATTER RADII OF A=20 ISOBARS

High-energy interaction cross sections of A = 20 nuclei (N-20, O-20, F -20, Ne-20, Na-20, Mg-20) on carbon were measured with accuracies of a pproximate to 1%. The nuclear matter r.m.s. radii derived from the mea sured cross sections show an irregular dependence on isospin projectio n. The largest difference in radii, which amounts to approximately 0.2 fm, has been obtained for the mirror nuclei O-20 and Mg-20. The influ ence of nuclear deformation and binding energy on the radii is discuss ed. By evaluating the difference in r.m.s. radii of neutron and proton distributions, evidence has been found for the existence of a proton skin for Mg-20 and of a neutron skin for N-20.