Disappearance of isospin effect in projectile fragmentation at intermediate energy

The 140~MeV/u ^40,48Ca+^9Be and ^58,64Ni+^9Bereactions are simulated by the statistical abrasion ablation model,and the simulation results are compared to the NationalSuperconducting Cyclotron Laboratory (NSCL) experimental data. Bycomparing the fragment isotopic distributions of ^40,48Ca and^58,64Ni, we study the isospin effect in the projectilefragmentation induced by the neutron-rich nuclei at intermediateenergy experimentally and theoretically. It is found that theisospin effect in projectile fragmentation decreases and evendisappears as the violence of the collision increases.