174 research outputs found
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
Applications of Skyrme energy-density functional to fusion reactions spanning the fusion barriers
The Skyrme energy density functional has been applied to the study of
heavy-ion fusion reactions. The barriers for fusion reactions are calculated by
the Skyrme energy density functional with proton and neutron density
distributions determined by using restricted density variational (RDV) method
within the same energy density functional together with semi-classical approach
known as the extended semi-classical Thomas-Fermi method. Based on the fusion
barrier obtained, we propose a parametrization of the empirical barrier
distribution to take into account the multi-dimensional character of real
barrier and then apply it to calculate the fusion excitation functions in terms
of barrier penetration concept. A large number of measured fusion excitation
functions spanning the fusion barriers can be reproduced well. The competition
between suppression and enhancement effects on sub-barrier fusion caused by
neutron-shell-closure and excess neutron effects is studied.Comment: 28 pages, 13 figures and 2 tables. accepted by Nucl. Phys.
Cross Section Limits for the Pb(Kr,n)118 Reaction
In April-May, 2001, the previously reported experiment to synthesize element
118 using the Pb(Kr,n)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 ions. The simple upper limit cross sections (1
event) were 0.9 and 0.6 pb for evaporation residue magnetic rigidities of 2.00
and 2.12 , 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
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
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