Charge-changing cross sections for Ca42-51 and effect of charged-particle evaporation induced by neutron-removal reactions

Abstract

Charge-changing cross sections sigma(CC) for Ca42-51 on a carbon target at around 280 MeV/nucleon have been measured. Though the existing point-proton radii r(p) of Ca isotopes increase as the neutron number increases, the measured sigma(CC) 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 sigma(CC) data sets for nuclides from C to Fe isotopes on C-12 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 sigma(CC) and r(p) using the current model indicates that sigma(CC) data for neutron-rich Ca isotopes (A >= 51) are highly sensitive to r(p). This high sensitivity potentially allows one to determine the r(p) of very neutron-rich nuclei.