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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.