Darmstadt 2008 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 24: Kern- und Teilchen-Astrophysik
HK 24.2: Gruppenbericht
Dienstag, 11. März 2008, 11:30–12:00, 2B
Low-energy cross sections of the BBN reaction d(α,γ)6Li by Coulomb dissociation of 6Li — •Michael Heil1, Klaus Suemmerer1, Fairouz Hammache2, Daniel Galaviz3, Stefan Typel4, and S246 collaboration1 — 1GSI Darmstadt,Germany — 2IPN Orsay, France — 3TU Darmstadt, Germany — 4GANIL Caen, France
The primordial abundances of D, (3He), 4He, and 7Li can be used to infer the baryon density of the Universe based on the framework of Big-Bang Nucleosynthesis (BBN). By precision measurements of the cosmic microwave background (CMB) an independent method became available recently. This lead to a renewed interest for BBN. Together with the recent observation of 6Li in old stars and the problems to reconcile calculated primordial 7Li abundances with those predicted on the basis of CMB results, the production of both, 6Li and 7Li in BBN has been reinvestigated. One important ingredient is the low-energy S-factor of the d-alpha radiative-capture reaction. Up to now, the only available experimental result by Kiener et al. (1991) introduced an uncertainty of about a factor of 20 in the 6Li yield. We have therefore reinvestigated the d-alpha reaction with the help of Coulomb dissociation (CD) of 6Li at 150 MeV/nucleon at GSI. CD is the only practical way to study the low-energy S-factor (which involves l=2 multipolarity) due to the large number of E2 photons contained in the equivalent-photon flux. Preliminary results indicate a drop of the S-factor as predicted by theory, contrary to the constant low-energy S-factor resulting from the previous study.