Properties of the Initial Participant Matter Interaction Zone in Near   Fermi-Energy Heavy Ion Collisions
  The sizes, temperatures and free neutron to proton ratios of the initial interaction zones produced in the collisions of 40 MeV/nucleon $^{40}$Ar + $^{112}$Sn and 55 MeV/nucleon$^{27}$Al + $^{124}$Sn are derived using total detected neutron plus charged particle multiplicity as a measure of the impact parameter range and number of participant nucleons. The size of the initial interaction zone, determined from a coalescence model analysis, increases significantly with decreasing impact parameter. The temperatures and free neutron to proton ratios in the interaction zones are relatively similar for different impact parameter ranges and evolve in a similar fashion. 
J. Wang, T. Keutgen, R. Wada, K. Hagel, S. Kowalski, T. Materna, L.   Qin, Z. Chen, J. B. Natowitz, Y. G. Ma, M. Murray, A. ...