High-energy breakup of Li6 as a tool to study the Big Bang nucleosynthesis reaction H2(α,γ)Li6

The recently claimed observations of non-negligible amounts of {sup 6}Li in old halo stars have renewed interest in the Big Bang nucleosynthesis (BBN) of {sup 6}Li. One important ingredient in the predicted BBN abundance of {sup 6}Li is the low-energy {sup 2}H({alpha},{gamma}){sup 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 {sup 2}H({alpha},{gamma}){sup 6}Li reaction using the breakup of {sup 6}Li at 150 A MeV. Even though we cannot separate experimentally the Coulomb contribution from the nuclear one, 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{sub 24} factor at low energies as predicted also by most other models. Consequently, we find even lower upper limits for the calculated primordial {sup 6}Li abundance than before.