⁷Be(n,p) cross section measurement for the Cosmological Lithium Problem at the n_TOF facility at CERN

Abstract

One of the most puzzling problems in Nuclear Astrophysics is the "Cosmological Lithium Problem", i.e the discrepancy between the primordial abundance of 7Li observed in metal poor halo stars [1], and the one predicted by Big Bang Nucleosynthesis (BBN). One of the reactions that could have an impact on the problem is 7Be(n,p)7Li. Despite of the importance of this reaction in BBN, the cross-section has never been directly measured at the energies of interest for BBN. Taking advantage of the innovative features of the second experimental area at the n_TOF facility at CERN, an accurate measurement of 7Be(n,p) cross section has been recently performed at n_TOF, with a pure 7Be target produced by implantation of a 7Be beam at ISOLDE. The experimental procedure, the setup used in the measurement and the results obtained so far will be here presented.