Sequential ejectile decays and uncorrelated breakup processes in the 14N + 159Tb reaction

From a study of particle-particle correlations, involving position-sensitive detector telescopes, conclusive evidence for sequential ejectile decay was found, and the relative importance of sequential decay and of breakup processes, which were observed to be uncorrelated in angle, could be determined

Selection of heavy ion reaction channels via particle K X-ray coincidences

To identify the residual nuclei in very asymmetric heavy-ion reactions heavy-ion K X-ray coincidences have been measured. The usefulness and limitations of this method are discussed, and its feasibility is demonstrated in a study of the 14N+197Au reaction at 140 MeV

Alpha-multiplicity in 12C induced reactions

Average a-multiplicities have been determined from a-a coincidence data in the 12C + 16°Gd reaction at bombarding energies of 120 MeV and 200 MeV. The results show that the incomplete fusion reactions a(12C, a) and a(12C, 2a), and the 3a-particle breakup a(12C, 3a) can account for the large inclusive c~-production cross sectio

Freeze-out configuration properties in the 197Au + 197Au reaction at 23 AMeV

Data from the experiment on the 197Au + 197Au reaction at 23 AMeV are analyzed with an aim to find signatures of exotic nuclear configurations such as toroid-shaped objects. The experimental data are compared with predictions of the ETNA code dedicated to look for such configurations and with the QMD model. A novel criterion of selecting events possibly resulting from the formation of exotic freeze-out configurations, "the efficiency factor", is tested. Comparison between experimental data and model predictions may indicate for the formation of flat/toroidal nuclear systems

Quasi-fission reactions as a probe of nuclear viscosity

Fission fragment mass and angular distributions were measured from the ^{64}Ni+^{197}Au reaction at 418 MeV and 383 MeV incident energy. A detailed data analysis was performed, using the one-body dissipation theory implemented in the code HICOL. The effect of the window and the wall friction on the experimental observables was investigated. Friction stronger than one-body was also considered. The mass and angular distributions were consistent with one-body dissipation. An evaporation code DIFHEAT coupled to HICOL was developed in order to predict reaction time scales required to describe available data on pre-scission neutron multiplicities. The multiplicity data were again consistent with one-body dissipation. The cross-sections for touch, capture and quasi-fission were also obtained.Comment: 25 pages REVTeX, 3 tables, 13 figures, submitted to Phys. Rev

Cross Section Limits for the 208^{208}Pb(86^{86}Kr,n)293^{293}118 Reaction

In April-May, 2001, the previously reported experiment to synthesize element 118 using the $^{208}$Pb($^{86}$Kr,n)$^{293}$118 reaction was repeated. No events corresponding to the synthesis of element 118 were observed with a total beam dose of 2.6 x 10$^{18}$ ions. The simple upper limit cross sections (1 event) were 0.9 and 0.6 pb for evaporation residue magnetic rigidities of 2.00 $T m$ and 2.12 $T m$, respectively. A more detailed cross section calculation, accounting for an assumed narrow excitation function, the energy loss of the beam in traversing the target and the uncertainty in the magnetic rigidity of the Z=118 recoils is also presented. Re-analysis of the primary data files from the 1999 experiment showed the reported element 118 events are not in the original data. The current results put constraints on the production cross section for synthesis of very heavy nuclei in cold fusion reactions.Comment: 7 pages, 2 figures. Submitted to EPJ

Status of data analysis and preliminary results of the CHIFAR experiment

In the CHIFAR experiment, carried out at the INFN-LNS laboratory, we studied reactions between beams of Sn-124, Xe-124 and Sn-112, accelerated at 20 AMeV, and targets of Ni-64, Zn-64 and Ni-58 by using the CHIMERA multi-detector coupled to 10 telescopes of the FARCOS array. The main topics of the experiment are the competition between reaction mechanisms and the Intermediate Mass Fragment production phenomenon, aiming to extend towards the low energy regime the studies performed in previous CHIMERA experiments carried out at beam energy of 35 AMeV. Status of data analysis arid preliminary results will be presented

First analysis of anisotropic flow with Lee--Yang zeroes

We report on the first analysis of directed and elliptic flow with the new method of Lee--Yang zeroes. Experimental data are presented for Ru+Ru reactions at 1.69 AGeV measured with the FOPI detector at SIS/GSI. The results obtained with several methods, based on the event-plane reconstruction, on Lee--Yang zeroes, and on multi-particle cumulants (up to 5th order) applied for the first time at SIS energies, are compared. They show conclusive evidence that azimuthal correlations between nucleons and composite particles at this energy are largely dominated by anisotropic flow.Comment: 5 pages, 3 figures, submitted to Phys. Rev. C Rapid Co