Charge-changing cross sections for Ca 42-51 and effect of charged-particle evaporation induced by neutron-removal reactions

Charge-changing cross sections σCC for Ca42-51 on a carbon target at around 280 MeV/nucleon have been measured. Though the existing point-proton radii rp of Ca isotopes increase as the neutron number increases, the measured σCC data show a significant decrease, which is against the expectation from a simple Glauber-like model. We found that this observed phenomenon could be attributed to the charged-particle evaporation effect induced by the neutron-removal reaction. By taking the evaporation effect into account, various σCC data sets for nuclides from C to Fe isotopes on C12 measured at around 280 MeV/nucleon are reproduced with a standard deviation of 1.6%. It is also clarified that this evaporation effect becomes negligibly small in the neutron-rich region. The evaluated relation between σCC and rp using the current model indicates that σCC data for neutron-rich Ca isotopes (A≥51) are highly sensitive to rp. This high sensitivity potentially allows one to determine the rp of very neutron-rich nuclei.