Coulomb dissociation as an indirect tool for measuring radiativecapture cross sections

1
Coulomb dissociation as an indirect tool for
measuring radiative-capture cross sections
1. Update on the 6Li(?,d)a Coulomb-dissociationex
periment at KaoS/GSI
2. Update on the 15C(?,n)14C Coulomb-dissociation
experiment at LAND/GSI
Klaus Sümmerer, GSI Darmstadt (Germany)
2
Update on the 6Li Coulomb-dissociationexperiment
at GSI
Klaus Sümmerer, GSI Darmstadt (Germany) for the
S246 collaboration

• Introduction Standard Big-Bang nucleosynthesis
  and 6,7Li production

• What do we know about the d(a,?)6Li reaction?

• Coulomb dissociation of 6Li at GSI at 150
  MeV/nucleon

• Preliminary results and problems

3
6,7Li production in standard Big-Bang
nucleosynthesis
4
Previous results for the S24 factor
Direct measurements a-particles on a thin D2
gas-jet target Measurements on and above 3
resonance
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Nuclear contribution in Coulomb dissociation?
Shyam, Baur and Banerjee Phys. Rev. C 44, 915
(1991)
At 26 A MeV, Coulomb processes are predicted to
dominate over nuclear contributions!
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Coulomb-dissociation experiment at GSI
Elab (6Li) 150 A MeV KaoS large-acceptance
spectrometer to analyze pa,pd
Experimental problem Identify a and d in
MWPC's ? momentum reconstruction
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Analysis steps of CD experiments
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Astrophysical S-factor of the d(a,?)6Li reaction
?
F. Hammache
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Open question Nuclear contribution?
New theoretical model CDXS (S.Typel) Coulomb,
nuclear interferences
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Energy dependence?
CDXS predicts more nuclear dominance at 26 A MeV
(FZK experiment)!
? analyze carefully the angular distributions ?
needs adjustment of optical potential
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Collaborators of the experiment

F. Hammache, S. Typel, K. Sümmerer, F. Attallah,
H. Geissel, M. Hellström, P. Koczon, E. Schwab,
K. Schwarz, P. Senger GSI, Postfach 110552,
D-64220 Darmstadt, Germany   D. Galaviz,
P.Mohr TU-Darmstadt D-64220 Darmstadt,
Germany J. Kiener, A. Coc, V. Tatischeff, J. P.
Thibaud CSNSM, IN2P3-CNRS, 91405 Orsay,
France   F. Schümann Ruhr-Universität Bochum,
Universitätsstr. 150, D-44780m Germany . O.
Sorlin IPN-Orsay, IN2P3-CNRS, 91406 Orsay,
France   D. Cortina, M. Caamano University
Santiago de Compostela, Spain   N. Iwasa,
RIKEN, Hirosawa, Wako, Saitama 351-01,
Japan   A.   Wagner Forschungszentrum Rossendorf,
D-01314 Dresden, Germany   B.Kohlmeyer Fachbereich
Physik, Philipps Universität, D-3550 Marburg,
Germany   W.Walus Institute of Physics,
Jagiellonian University, PL-30-059 Krakow, Poland


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Update on the 15C(?,n)14C Coulomb-dissociationexp
eriment at GSI
U. Datta Pramanik et al. (GSI Darmstadt) M.
Heil (FZ Karlsruhe), R. Reifarth (LANL) et al.

• Introduction Discrepancies between direct and
  indirect measurements of the 14C(n,?)15C reaction

• Results from the Coulomb dissociation of 15C

• Reanalysis of the 14C(n, ?)15C reaction

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Motivation

• Astrophysics 14C(n,?)15C plays a role in
• Inhomogeneous Big-Bang nucleosynthesis
• Neutron-induced CNO cycle
• Light-nuclei r-process reaction network

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Comparison between direct and indirect
measurements (1992 2003)
Coulomb dissociation MSU sn,?(23keV) 2.6
0.9 µb A.Horvath et. al., Astrophys. J. 570, 926
(2002) GSI sn,?(23keV) 4.3 1.0 µb U.Datta
Pramanik et. al., Phys. Lett. B 551, 61
(2003) RIKEN sn,?(23keV) 4.1 0.4
µb T.Nakamura et al. NPA 722, 301c (2003)
Disagreement between direct and CD measurements
!!!
M.Heil
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Experimental results for CD of 15C
Data LAND/GSI (U. Datta Pramanik et al.) Theory
S. Typel (priv.comm.)
S. Typel
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Re-analysis of the FZK (n,?) experiments
Changes compared to the 1992 FZK
experiment (using the identical 14C sample from
LANL)

• Large-volume HPGe-detector
• better peak-to-Compton ratio

• Less background
• cooling of sample container over 12 years

• Efficiency and dead-time corrections
• performed with background ?-lines from container

• Decay properties of 15C
• I?(5.298 MeV ?-line) 0.632 instead of 0.68

M.Heil
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Collaborators of the experiments
Coulomb breakup U. Datta Pramanik, T. Aumann, K.
Boretzky, B.V. Carlson, D. Cortina, Th.W. Elze,
H. Emling, H. Geissel, A. Grünschloss, M.
Hellstroem, S. Ilievsky, J.V. Kratz, R. Kulessa,
Y. Leifels, A. Leistenschneider, E. Lubkiewicz,
G. Münzenberg, P. Reiter, H. Simon, K. Sümmerer,
E. Wajda, W. Walus
GSI Darmstadt Saha Inst. Univ. Mainz CTA
San Jose dos Campos Univ. Santiago de Compostela
Univ. Frankfurt Univ. Jagellonski Krakau LMU
München TU Darmstadt