High-energy break-up of 6Li as a tool to study the Big-Bang nucleosynthesis reaction 2H6Li

The recently claimed observations of non-negligible amounts of 6Li in old halo stars have renewed interest in the big bang nucleosynthesis (BBN) of 6Li. One important ingredient in the predicted BBN abundance of 6Li is the low-energy 2 H ( α , γ ) 6 Li cross section. Up to now, the only available experimental result for this cross section showed an almost constant astrophysical S -factor below 400 keV, contrary to theoretical expectations. We report on a new measurement of the 2 H ( α , γ ) 6 Li reaction using the break-up of 6Li at 150 A  MeV. We find clear evidence for Coulomb-nuclear interference by analyzing the scattering-angular distributions. This is in-line with our theoretical description which indicates a drop of the S 24 -factor at low energies as predicted also by most other models. Consequently, we find even lower upper limits for the calculated primordial 6Li abundance than before.