Determination of the 3He(α, γ)7Be and 6Li(p, γ)7Be astrophysical factors down to zero energy using the asymptotic normalization coefficients.

The p - p-chain reaction ³He(α, γ)⁷Be can sensitively influence the prediction of the ⁷Be and ⁸B neutrino fluxes. Despite its importance, the knowledge of its reaction cross section at energies of the core of the Sun (15 keV 30 keV) is limited and the accuracy far from the desired 3% level. In the present paper the indirect measurement of the external capture contribution using the asymptotic normalization coefficient (ANC) technique is reported. The angular distributions of deuterons emitted in the ⁶Li(³He,d)⁷Be α-transfer reactions were measured and the ANCs extracted from the scaling of distorted-wave Born approximation (DWBA) and coupled-channel (CC) calculations. Then, the astrophysical S-factor for the ³He(α, γ)⁷Be reaction was calculated assuming E1 direct capture and the zero energy value turned out to be 0.534 0.025 keVb. Both our experimental and theoretical approaches were benchmarked through the analysis of the ⁶Li(p,γ)⁷Be astrophysical factor, with interesting astrophysical applications to the understanding of the primordial lithium problem. In particular, the present work disfavors the occurrence of a claimed 200 keV resonance in the astrophysical factor. [ABSTRACT FROM AUTHOR]