New measurement of the cross section of the Big Bang Nucleosynthesis reaction D(α,γ )⁶Li and its astrophysical impact

The recent observations of non-negligible amounts of ⁶Li in old halo stars have renewed interest in the Big-Bang Nucleosynthesis (BBN) of ⁶Li. The deduced primordial ⁶Li abundance was found to be unexpectedly large compared to the BBN predictions. One important ingredient in the BBN predictions is the low-energy D(α,γ )⁶Li cross section. Up to now, the only available experimental result for this cross section introduced an error of about a factor of 20 in the ⁶Li abundance at the energies of astrophysical interest (Ecm ≤ 300 keV). This uncertainty arises from the discrepancy between the theoretical low energy dependence of the S-factor and the experimental data. Accordingly, new measurements of the cross section of the D(α,γ)⁶Li reaction using Coulomb dissociation (CD) of ⁶Li at 150 A MeV have been performed recently at GSI. The preliminary GSI results, which indicate a drop of the S-factor as predicted by theory will be presented as well their impact on the calculated ⁶Li abundance as a function of the baryon-tophoton ratio.