AZIMUTHAL DEPENDENCE OF THE DIRECTED FLOW IN COLLISIONS UP TO 95 MEV U - FROM INPLANE TO OUT-OF-PLANE ENHANCEMENT/

Nucleus-nucleus reaction mechanisms at incident energies below 10 MeV/ u are governed by mean field effects. Nucleon-nucleon collisions begin to become important as the energy increases above the Fermi energy. T his evolution manifests itself experimentally in the modification of t he directed flow of the emitted participant (mid-rapidity) nucleons. I n the reaction plane, it is expressed by the flow parameter [1]. Anoth er aspect lies in the azimuthal distribution of particles relative to the reaction plane. At high energies, a maximum in the direction perpe ndicular to the reaction plane on both sides was named squeeze-out-eff ect [2]. Conversely, below 100 MeV/u, maxima in the reaction plane hav e been observed for the light systems of Ar + V : rotation-like effect [3]. It was studied as a Function of energy, impact parameter and emi tted particle mass in the collisions of Ar-40 on Al-27 at energies fro m 36 to 65 MeV/u [4]. The latter study has been extended up to 95 MeV/ u and measurements have been made for the Zn-64 + Ni-58 system at 5 en ergies from 35 to 79 MeV/u.