Disappearance of isospin effect in projectile fragmentation at intermediate energy

The 140 MeV/u Ca-40,Ca-48+ Be-9 and Ni-58,Ni-64+ Be-9 reactions are simulated by the statistical abrasion ablation model, and the simulation results are compared to the National Superconducting Cyclotron Laboratory (NSCL) experimental data. By comparing the fragment isotopic distributions of Ca-40,Ca-48 and Ni-58,Ni-64, we study the isospin effect in the projectile fragmentation induced by the neutron-rich nuclei at intermediate energy experimentally and theoretically. It is found that the isospin effect in projectile fragmentation decreases and even disappears as the violence of the collision increases.