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

Abstract

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.