Newly measured ⁷Be+n reaction cross sections and resonance study for the BBN

The cosmological ⁷Li problem is still an open question although several solutions have been proposed for years. Since the primordial ⁷Li abundance strongly depends on the ⁷Be production and destruction rate during the Big-Bang nucleosynthesis (BBN), those of the main destruction processes ⁷Be(n,p)⁷Li and ⁷Be(n,α)⁴He need to be determined. In spite of several recent experimental efforts, there are still some uncertainties at the most relevant energies.

We have performed indirect measurements of both of these reactions by the Trojan Horse Method (THM). The experiments were performed both at the EXOTIC, INFN-LNL, and at the Center-for-Nuclear-Study Radioactive Ion Beam (CRIB) separator in collaboration. We will present the results of the latter experiment.

We observed both the ⁷Be(d,⁷Lip)¹H and ⁷Be(d,αα)¹H reactions in inverse kinematics by a single measurement, approaching the ⁷Be(n,p)⁷Li and ⁷Be(n,α)⁴He reactions in quasi-free kinematics, respectively. The (n,p₁) yields were successfully extracted for the first time in the relevant energy region. We will discuss the normalization of the present THM cross sections for the (n,p₀), (n,p₁) and (n,α) by multichannel R-matrix analysis, and possible astrophysical implications.