Two-neutron removal cross sections from C 15,16 at around 240 MeV/nucleon

The cross sections for two-neutron removal from C15,16 on a carbon target have been measured at around 240 MeV/nucleon. The measured cross section for C15 is smaller than for C16. The trends of the cross sections for C15,16 are inconsistent with the previously reported experimental data, but in agreement with the theoretical predictions based on eikonal-model calculations. Based on the present results of C15,16 combined with the available experimental data on C17-20, an odd-even staggering of the two-neutron removal cross sections along the neutron-rich carbon isotopic chain from C15 to C20 is observed, and this feature is well reproduced by the theoretical calculations.