Effective Nucleon Masses from Heavy Ion Collisions
  We probe the momentum dependence of the isovector mean-field potential by comparing the energy spectra of neutrons and protons emitted in $^{112}$Sn+$^{112}$Sn and $^{124}$Sn+$^{124}$Sn collisions at incident energies of E/A=50 and 120 MeV. We achieve experimental precision that discriminates between different momentum dependencies for the symmetry mean-field potential. Comparisons of the experimental results to Improved Quantum Molecular Dynamics model calculations with Skyrme Interactions indicate small differences between the neutron and proton effective masses. 
D.D.S. Coupland, M. Youngs, W.G. Lynch, M.B. Tsang, Z. Chajecki, Y. X.   Zhang, M.A. Famiano, T.K. Ghosh, B. Giacherio, M. A...
nucl-ex