Program - Brookhaven National Laboratory

Schwerionenforschung, Germany. R B-Collaboration, Technische Universitaet Darmstadt, Germany. C.
Langer, National Superconducting Cyclotron Lab, Michigan, USA. J. Marganiec, Extreme Matter
Institute, Darmstadt, Germany.
Model calculations of r-process nucleosynthesis within a neutrino-driven wind scenario indicate that light,
neutron-rich nuclei, may have a crucial influence on the final r-process abundances [1]. Sensitivity studies
identified the most influential reactions, which include succesive (n,γ) reactions running through the isotopic
chain of neutron-rich boron isotopes [2]. However, nuclear reaction rates of unstable nuclei far from stability
are rarely known and very difficult to determine experimentally. Therefore, the corresponding time-reversed
reactions were investigated in a kinematically complete measurement in inverse kinematics via Coulomb
dissociation at relativistic energies. A primary beam of 40 Ar was fragmented and the desired isotopes
were separated from the primary beam using a fragment separator (FRS). A secondary beam of 14,15 B was
then directed onto a Pb-target to investigate the interaction with the Coulomb field. The experiment was
performed at the LAND/R 3 B setup at the GSI Helmholtzzentrum fuer Schwerionenforschung GmbH.
[1] M. Terasawa et al., APJ, 562, 470-479, (2001) [2] T. Sasaqui et al., APJ 634, 1173-1189, (2005)
OC 3 2:20 PM
R-matrix Analysis of Reactions in the 9 B Compound System
M.W. Paris, G.M. Hale
Theoretical Division, Los Alamos National Laboratory, Los Alamos NM 87545, USA
Reactions in the 9 B compound system are analyzed with the R-matrix code EDA, developed by Hale
and collaborators, using all the known elastic and reaction data, in a four-channel treatment. The data
include elastic 3 He+ 6 Li differential cross sections from 0.7 to 2.0 MeV, integrated reaction cross sections for
energies from 0.7 to 5.0 MeV for 6 Li( 3 He,p) 8 Be* and from 0.4 to 5.0 MeV for the 6 Li( 3 He,d) 7 Be reaction.
Capture data have been added to the previous analysis with integrated cross section measurements from 0.7
to 0.825 MeV for 6 Li( 3 He,γ) 9 B. The resulting resonance parameters are compared with tabulated values,
and previously unidentified resonances are noted. The possible relevance of this analysis for big bang
nucleosynthesis and other astrophysical applications is addressed and < σv > data for these reactions are
presented.
OC 4 2:40 PM
Astrophysical Sbare(E) Factor of the 6 Li+d and 7 Li+p Reactions
J. Kasagi
Research Center for Electron Photon Science, Tohoku University
K.H. Fang
School of Nuclear Science and Technology, Lanzhou University
Cross sections of nuclear reactions far below the Coulomb barrier are very important for various astrophysical
applications as well as for thermal nuclear fusion experiments. Since the cross section σ(E) decreases
nearly exponentially as E decreases, it is converted into an astrophysical S(E) factor by the definition
S(E) = σ(E)Eexp(2πη(E)). In the very low energy region, the screening effect of the environment (for ex.
surrounding electrons) enhances the S(E) strongly. Thus, one faces the difficulty of deducing the nuclear
Sbare(E), which corresponds to the nuclear reaction between two bare nuclei. Although the Sbare(E) in the
6 Li+d and 7 Li+p reactions have been reported in [1], the enhancement of the S(E) cannot be explained well
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