7Be(n,p)7 Li 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 Li observed in metal poor halo stars (Asplund et al. in Astrophys J 644:229–259, 2006, [1]), and the one predicted by Big Bang Nucleosynthesis (BBN). One of the reactions that could have an impact on the problem is Be(n,p) Li. 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 (Sabate-Gilarte et al. in Eur Phys J A 53:210, 2017, [2]; Weiss et al. in NIMA 799:90, 2015, [3]), an accurate measurement of Be(n,p) cross section has been recently performed at n TOF, with a pure Be target produced by implantation of a Be beam at ISOLDE. The mesurement started in April 2016 and lasted for two months. The experimental procedure, the setup used in the measurement and the results obtained so far will be here presented.