Constraining the Primordial Lithium Abundance: New Cross Section Measurement of the 7Be + n Reactions Updates the Total 7Be Destruction Rate

The cosmological lithium problem (CLP) stems from the outstanding discrepancy between theoretical predictions and astronomical observations of primordial lithium abundances. For the radiogenic production of Li-7, Be-7 plays a pivotal role in the Big Bang nucleosynthesis (BBN). Nevertheless, the data for neutron-induced Be-7 destruction processes were still sparse, and especially lacked information on the contributions of transitions to the Li-7 excited states. In this work, we have determined the Be-7 (n,p(0))(7) Li, Be-7 (n,p(1))(7) Li*, and Be-7 (n,alpha)(4) R-matrix fit, providing an improved uncertainty evaluation of the (n,p(0)) (n,p(1)) (n,p(0)) (n,p(1)) PRIMAT. As a consequence, the present nuclear-physics data offers a reduction of the predicted Li-7 abundance by about one-tenth, which would impose a stricter constraint on BBN and head us in the correct direction to the CLP solution.

Automated summary

The cosmological lithium problem arises from discrepancies between theoretical predictions and observations of primordial lithium abundances. This study determined the role of Be-7 in Big Bang nucleosynthesis, providing a more precise evaluation of Li-7 abundance and offering a potential solution to the CLP.