The azimuthal distributions of light particles relative to the reaction plane have been measured for several bins of experimentally estimated impact parameters in the reactions of Zn-64 + Ni-58 at energies between 35 and 79 MeV/u. An in-plane enhancement for mid-rapidity Z= 1, 2, 3 particles is observed at low incident energy but gradually evolves to out-of-plane enhancement (squeeze-out effect) with increasing energy. This evolution depends on the impact parameter in a way similar to the flow parameter. The energies for this system at which the azimuthal distribution is uniform are lower than the corresponding balance energies.
Popescu, R. ; El Masri, Youssef ; et. al. From Inplane To Out-of-plane Enhancement of the Directed Flow in Zn-64 On Ni-58 Collisions Between 35 and 79 Mev/u. In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics, Vol. 331, no. 3-4, p. 285-289 (1994)
