Interaction cross section study of the two-neutron halo nucleus 22C

The interaction cross sections (σ_I) of the very neutron-rich carbon isotopes ¹⁹C, ²⁰C and ²²C have been measured on a carbon target at 307, 280, and 235 MeV/nucleon, respectively. A σ_I of 1.280 ± 0.023 b was obtained for ²²C, significantly larger than for ^19,20C, supporting the halo character of ²²C. A ²²C root-mean-squared matter radius of 3.44 ± 0.08 fm was deduced using a four-body Glauber reaction model. This value is smaller than an earlier estimate (of 5.4 ± 0.9 fm) derived from a σ_I measurement on a hydrogen target at 40 MeV/nucleon. These new, higher-precision σ_I data provide stronger constraints for assessing the consistency of theories describing weakly bound nuclei.