Scattering of neutrons on -particles in three-dimensional space

This letter demonstrates that there are some mistakes in the article of Roshan et al ( Pramana – J. Phys. 90(3) : 30, 2018 ) in dealing with the scattering of neutrons on -particles in three-dimensional space. In fact, there is no one-to-one correspondence between the incident neutron energy and the scattering angle of the -particle even if they have definite velocities before scattering. Instead, the situation is complex, and all the scattered -particles will emit in a cone, which is called the velocity cone. At each scattering angle, which is smaller than the apex angle of the velocity cone, there are two groups of -particles with different kinetic energies.