High-energy break-up of 6Li as a tool to study the Big-Bang nucleosynthesis reaction 2H(α,γ)6Li

Abstract The recently claimed observations of non-negligible amounts of 6 Li in old halo stars have renewed interest in the big bang nucleosynthesis (BBN) of 6 Li. One important ingredient in the predicted BBN abundance of 6 Li 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 6 Li 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 6 Li abundance than before.