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

The interaction cross sections ( σ I ) of the very neutron-rich carbon isotopes 19 C, 20 C and 22 C 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 22 C, significantly larger than for 19,20 C, supporting the halo character of 22 C. A 22 C 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.