In this paper, we investigate the possible mechanisms, which are responsible for the production of slow target fragments with energy ≤400 MeV that are emitted from interactions of 28Si nucleus with emulsion nuclei at energy 14.6 GeV per nucleon. Angular distributions of slow fragments are compared with the corresponding results from collisions of 1H, 3He, 4He, 7Li and 12C with emulsion at the energy range 2.2–3.7AGeV. We investigate the effects of both projectile energy and mass number on the angular distributions for slow secondary charged fragments called gray and black track producing particles. The average emission angles are found to be 64◦ and 82◦ for gray and black tracks, respectively. These values are nearly constant for all compared experiments. There are two different mechanisms of gray particle production in forward and backward directions while there is a single symmetric mechanism for black particles in both directions. The temperatures are found to be 58 and 6MeV for systems of emissions for gray and black particles, respectively. There are strong effects of target size on those mechanisms. The emission system of these particles becomes slower and shows low temperature with the increase in volume of target nucleus.