Semirelativistic antisymmetrized molecular dynamics for the production of energetic neutrons in intermediate-energy heavy-ion reactions

Relativistic corrections have been made in the nonrelativistic antisymmetrized molecular dynamics (AMD) simulations to apply to the high-energy neutron production in the 12C + 12C and 16O + 12C collisions at incident energies of 290 and 400 MeV/nucleon. The corrections are made in kinematics alone and neither nucleon-nucleon inelastic scatterings nor meson productions are taken into account, and AMD with the relativistic corrections is called semirelativistic AMD. The three-nucleon collision (3NC) and Fermi boost in the collision processes are taken into account in the nonrelativistic AMD. Since the relativistic corrections tend to compensate in each other, the difference between the semirelativistic and nonrelativistic results become small. High-energy tails of the available experimental neutron double-differential cross sections, especially at larger angles, are well reproduced by AMD with the 3NC term both with nonrelativistic and semirelativistic simulations. These results indicate that the high-energy neutrons are dominantly produced by the 3NC process in this incident energy range.