Constraining the Primordial Lithium Abundance: New Cross Section Measurement of the 7 Be + n Reactions Updates the Total 7 Be 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 7Li, 7Be plays a pivotal role in the Big Bang nucleosynthesis (BBN). Nevertheless, the data for neutron-induced 7Be destruction processes were still sparse, and especially lacked information on the contributions of transitions to the 7Li excited states. In this work, we have determined the 7Be${(n,{p}_{0})}^{7}$Li, 7Be${(n,{p}_{1})}^{7}$Li*, and 7Be${(n,\alpha )}^{4}$He reaction cross sections by means of the Trojan Horse method. The present and the previous data were analyzed together by a multichannel R-matrix fit, providing an improved uncertainty evaluation of the $(n,{p}_{0})$ channel and the first-ever quantification of the $(n,{p}_{1})$ contribution in the BBN-relevant energy range. We implemented the revised total reaction rate summing both the $(n,{p}_{0})$ and $(n,{p}_{1})$ contributions in a state-of-the-art BBN code PRIMAT. As a consequence, the present nuclear-physics data offers a reduction of the predicted 7Li abundance by about one-tenth, which would impose a stricter constraint on BBN and head us in the correct direction to the CLP solution.