Reactions of the halo systems Be-11 and Li-11 (at 460 and 280 MeV/nucleon) with a carbon target demonstrate that (n + Li-9) has an (unbound) l = 0 ground state very close to the threshold. The ...neutron halo of Li-11 has appreciable (1s(1/2))(2) and (0p(1/2))(2) components.
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.
Transverse and longitudinal momentum distributions of Li-9 fragments from Li-11 break-up reactions in C, Al and Pb targets have been measured at 280 MeV/u. The two-neutron removal cross-section was ...measured to be sigma(-2n), = 0.26 +/- 0.02 b for the carbon target, sigma(-2n) = 0.47 +/- 0.08 b for the aluminum target and sigma(-2n), = 1.9 +/- 0.4 b for the lead target. No significant difference is observed between the narrow widths (FWHM approximate to 47 MeV/c) of the transverse and longitudinal momentum distributions of the Li-9 fragments. The physical implications of this are discussed.
The present study examined the development of phonological and reading skills in 171 students (98 males, 73 females) from the beginning of first grade (Time 1) to the end of second grade (Time 4). ...Based on their reading and intelligence scores at the end of second grade, these students were placed into nondisabled (ND), reading disabled (RD), or garden-variety poor reading (GV) groups. Although each group made gains in phonological processing, large differences were found between the ND and RD/GV groups. The RD and GV groups performed similarly on many of the tasks. Consistent with the literature, it was found that intelligence does not differentiate between good and poor readers. The most important finding of the present study was that reader-group membership at Time 4 could be very accurately determined from students' Time 1 scores. All of the children in the RD and GV groups were correctly identified, and only 3 of the 148 ND children were misclassified, indicating that children at risk for reading difficulties can be very accurately identified very early in their academic experiences.
Neutron and He-6 momentum distributions from He-8 break-up reactions in a C target have been measured at 240 MeV/u. The two-neutron removal cross section was found to be sigma(-2n) = 0.27 +/- 0.03 b. ...The nature of the momentum distributions is interpreted in some simple reaction scenarios.
Multifragment decays of heavy nuclei have been studied at the ALADIN spectrometer system at beam energies between 100 and 1000 MeV per nucleon. The observed fragment distributions signal a ...universality of spectator decays at bombarding energies
E
A
≥ 400
MeV
. The role of the radial flow for the fragmentation process is explored by comparing fragment distributions measured for Au+Au collisions at
E
A
= 100
MeV
in central collisions and at
E
A
= 1000 MeV
in more peripheral reactions. At both energies the maximum multiplicity of intermediate mass fragments (IMFs) 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
E
A
= 100 MeV
may be related to a reduction of the density in momentum space which is caused by a large collective expansion velocity component.
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