The Cosmological Lithium Problem refers to the large discrepancy between the abundance of primordial 7Li predicted by the standard theory of Big Bang Nucleosynthesis and the value inferred from the so-called ”Spite plateau” in halo stars. A possible explanation for this longstanding puzzle in Nuclear Astrophysics is related to the incorrect estimation of the destruction rate of 7Be, which is responsible for the production of 95% of primordial Lithium. While charged-particle induced reactions have mostly been ruled out, data on the 7Be(n,α) and 7Be(n,p) direct reactions have been so far scarce or completely missing, so that a large uncertainty still affects the abundance of 7Li predicted by the standard theory of Big Bang Nucleosynthesis.
Both reactions have been recently measured at the second experimental area of the n_TOF facility at CERN, taking advantage of the very high instantaneous neutron flux of this new installation. Data in a wide neutron energy range have been obtained for both reactions, with different setups based on silicon detectors. For the (n,p) reaction, an isotopically separated target was obtained by implantation of a 7Be beam produced at ISOLDE, demonstrating also for the first time the feasibility of neutron measurements on isotopes produced at Radioactive Beam Facilities.
After an introduction on the n_TOF facility and the Cosmological Lithium Problem, the results of the measurements will be presented, together with their implications for Nuclear Astrophysics.
