Multi-fragment decays of
129Xe,
197Au and
238U projectiles in collisions with Be, C, Al, Cu, In, Au and U targets at energies between
E
A
= 400
and 1000 MeV have been studied with the ALADIN ...forward-spectrometer at SIS. By adding an array of 84 SiCsI(Tl) telescopes the solid-angle coverage of the setup was extended to
θ
lab = 16°. This permitted the complete detection of fragments from the projectile-spectator source.
The dominant feature of the systematic set of data is the
Z
bound universality that is obeyed by the fragment multiplicities and correlations. These observables are invariant with respect to the entrance channel if plotted as a function of
Z
bound, where
Z
bound is the sum of the atomic numbers
Z
i
of all projectile fragments with
Z
i
⩾ 2. No significant dependence on the bombarding energy nor on the target mass is observed. The dependence of the fragment multiplicity on the projectile mass follows a linear scaling law.
The reasons for and the limits of the observed universality of spectator fragmentation are explored within the realm of the available data and with model studies. It is found that the universal properties should persist up to much higher bombarding energies than explored in this work and that they are consistent with universal features exhibited by the intranuclear cascade and statistical multifragmentation models.
Neutron and
6He momentum distributions from
8He break-up reactions in a C target have been measured at 240 MeV/u. The two-neutron removal cross section was found to be
σ
−2
n
= 0.27 ± 0.03 b. The ...nature of the momentum distributions is interpreted in some simple reaction scenarios.
Fragment distributions have been measured for Au+Au collisions at ital E/ital A=100 and 1000 MeV. A high detection efficiency for fragments was obtained by combining the ALADIN spectrometer and the ...MSU-Miniball/WU-Miniwall array. At both energies the maximum multiplicity of intermediate mass fragments (IMF) normalized to the size of the decaying system is about one IMF per 30 nucleons but the element distributions show significant differences. Within a coalescence picture the suppression of heavy fragments in central collisions at ital E/ital A=100 MeV may be related to a reduction of the density in momentum space which is caused by the collective expansion.
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.
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.
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