C. Cerruti

Evidence for collective expansion in light-particle emission following Au+Au collisions at 100, 150 and 250 A·MeV

Abstract Light-particle emission from Au+Au collisions has been studied in the bombarding-energy range 100–250 A ·MeV, using ΔE − E R telescopes in coincidence with the FOPI detector in its phase I configuration. Center-of-mass energy spectra have been measured for Z = 1,2 isotopes emitted in central collisions at CM polar angles between 60° and 90°. Evidence for a collective expansion is reported, on the basis of the mean kinetic energies of hydrogen isotopes. Comparison is presented with statistical calculations (WIX code). For CM kinetic energy spectra, fair agreement is found between data and a recently developed transport model.

Sideward flow in Au + Au collisions at 400 A.MeV

Abstract We present new experimental data obtained with the FOPI detector at SIS, for the Au + Au heavy-ion collisions at 400 A MeV incident energy. The sideward flow, determined from a method without reaction-plane reconstruction, and the nuclear stopping are studied as a function of the centrality of the collisions. In order to study the nuclear in-medium effects, which act on the NN cross sections and potential and hence on experimental observables like the nuclear-matter flow and stopping, these results are compared with the predictions of two different QMD versions. The first one offers a fully microscopic calculation of the cross sections and potential in the G-matrix formalism and naturally includes the in-medium effects (this version is for the first time confronted with experiment). The second one uses a standard Skyrme potential plus a momentum-dependent term in order to mimic the in-medium effects.

Out-of-plane emission of nuclear matter in Au+Au collisions between 100 and 800 AMeV

Abstract We present new experimental results concerning the azimuthal distributions of proton-likes, light and intermediate mass fragments at midrapidity for Au(100–800 A MeV) +Au collisions measured with the FOPI phase-I detector at GSI in Darmstadt. The azimuthal distributions are investigated as a function of the collision centrality, the incident energy, the fragment charge and transverse momentum. The azimuthal anisotropy is maximum for impact parameters around 7 fm. Intermediate mass fragments present a stronger out-of-plane emission signal than light fragments and a saturation is reached for Z ⩾ 4. The azimuthal anisotropy increases with the fragment transverse momentum and decreases as the incident energy increases. The azimuthal anisotropy of Z = 2 particles investigated as a function of the scaled fragment transverse momentum follows an universal curve for bombarding energies between 250–800 A MeV. A signature for a transition from in-plane to out-of-plane emission is evidenced at the lowest beam energies.

Study of the 129Xe + natAg, 197Au systems at 23.7 and 27 MeV/u

Abstract We present some inclusive data and a few coincident results obtained for the 129 Xe + nat Ag, 197 Au systems at 23.7 MeV/u and 27 MeV/u at GANIL. The reaction products have been detected between 5 and 13° in the laboratory. In addition to fragmentation products, we found products with kinetic energies, atomic numbers and masses substantially smaller than those of the projectile. We have studied different possibilities for their formation and are led to conclude that they are coming from interactions where three or more nuclei of significant size are present after the collision. It is likely they are coming from successive binary decays and we discuss different possibilities for such processes.