Deflection of Nonequilibrium Light Particles by the Nuclear Mean Field

The sign of the average emission angle of nonequilibrium light particles was determined from the circular polarization of coincident γ rays emitted from residual nuclei for ¹⁴N-induced reactions on ¹⁵⁴Sm at E/A=20 and 35 MeV. Light particles (p,d,t,α) are preferentially emitted to negative angles. This effect is consistent with deflection of the particles by the attractive nuclear mean field. Numerical solutions of the Boltzmann-Uehling-Uhlenbeck equation demonstrate that the experimental result is sensitive to the interplay between the nuclear mean field and nucleon-nucleon collisions.