High-energy neutron emission from the reactions of ${}^{40}\mathrm{Ar}$ and ${}^{20}\mathrm{Ne}$ on a natural copper target at $E_{\mathrm{inc}}/A=400$ to 600 MeV is studied, examining a possible signature of nucleon-nucleon short-range correlations (SRCs) in the high-energy/high-momentum tails in the neutron spectra, using available experimental datasets of Iwata et al. [Phys. Rev. C 64, 054609 (2001)]. Semirelativistic antisymmetrized molecular dynamics (SrAMD) is utilized with a three-nucleon collision (3NC) term, in which each nucleon is boosted with Fermi motion plus an empirical high-momentum tail (HMT) in the collision process, where the HMT is closely related to SRC. High-energy/high-momentum tails observed above the projectile velocity at forward angles in the experimental neutron spectra, which are commonly observed in Iwata et al.'s datasets, are attributed to originate from non-physics-related origins. Those at ${\theta }_{\mathrm{lab}}\ge {60}^{\circ }$ are started below the projectile velocity and attributed to originate from physics-related processes, since these can be reproduced by the SrAMD simulations with HMTs in the Fermi boost. This observation suggests that the high-energy/high-momentum tails are affected by the short-range correlations and may characterize the nature of SRCs that appear in the heavy-ion collisions, though the experimental data quality in accuracy and statistics makes it difficult to make conclusive remarks. Although the positive correlation between HMTs in the Fermi boost and the enhancement of the high-energy/high-momentum tails in the neutron spectra is observed, no flattening of the momentum spectra in the $K^4$-weighted representation of neutron cross section $K^{4}d{\sigma }^2/dKd\mathrm{\Omega }$ is observed in the SrAMD simulations.

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• Low & intermediate energy heavy-ion reactions
• Nuclear reactions