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Background: The Li 6 ( p , γ ) Be 7 cross section influences a variety of astrophysical scenarios, including big-bang and stellar nucleosynthesis. In recent years, conflicting results of direct measurements have been published, reporting contradictory low-energy trends. Purpose: To shed light on the contradiction between the existing data sets, the reaction was studied using the asymptotic normalization coefficient (ANC) technique which was up-to-now never used for this reaction. Methods: To derive the ANC, the Li 6 ( He 3 , d ) Be 7 transfer reaction, studied at the Department of Physics and Astronomy of the University of Catania and at the John. D. Fox Superconducting Accelerator Laboratory at Florida State University, was re-analyzed, focusing on the proton transfer mechanism [the α transfer process is discussed by Kiss et al. [Phys. Lett. B 807, 135606 (2020)]. The energy of the He 3 beam impinging on a Li 6 target was E lab = 3 MeV and E lab = 5 MeV. The yield of the emitted deuterons was measured with high precision by using silicon Δ E - E telescopes. Results: From the DWBA analysis of the angular distributions of the emitted deuterons populating the ground ( E * = 0.0 MeV; 3 2 − ) and the first excited ( E * = 0.429 MeV ; 1 2 − ) states of Be 7 , the ANCs for the Li 6 + p → Be 7 system were deduced. Furthermore, the recently measured Li 6 ( p , γ ) Be 7 reaction cross sections [Piatti , Phys. Rev. C 102, 052802 (2020)] were also analyzed within this theoretical framework. Excellent agreement was found between ANC values derived indirectly and those determined from the direct data, which strengthens the conclusion of the present work. The astrophysical S factor—at energies characterizing the Sun—for the Li 6 ( p , γ ) Be 7 reaction was calculated using the weighted mean of the experimentally derived ANC values. Conclusions: The result of the present comprehensive study supports the extrapolation of Piatti [Phys. Rev. C 102, 052802 (2020)], Dong [J. Phys. G Nucl. Partic. 44, 045201 (2017)], and Gnech and Marcucci [Nucl. Phys. A 987, 1 (2019)], and thus disfavors the conclusions drawn by He [Phys. Lett. B 725, 287 (2013)] and Xu [Nucl. Phys. A 918, 61 (2013)].

The detection of the neutrinos produced in the p − p chain and in the CNO cycle can be used to test the Standard Solar Model. The 3He( α , γ )7Be reaction is the first reaction of the 2nd and 3rd branch of the p − p chain, therefore, the uncertainty of its cross section sensitively influences the prediction of the 7Be and 8B neutrino fluxes. Despite its importance and the large number of experimental and theoretical works devoted to this reaction, the knowledge on the reaction cross section at energies characterizing the core of the Sun (15 keV - 30 keV) is limited and further experimental efforts are needed to reach the desired (≈ 3%) accuracy. The precise knowledge on the external capture contribution to the 3He( α , γ )7Be reaction cross section is crucial for the theoretical description of the reaction mechanism. In the present work the indirect measurement of this external capture contribution using the Asymptotic Normalization Coefficient (ANC) technique is reported. To extract the ANC, the angular distributions of deuterons emitted in the 6Li(3He,d)7Be α-transfer reaction were measured with high precision at E H 3 e = 3.0 MeV and E H 3 e = 5.0 MeV. The ANCs were then extracted from comparison of DWBA calculations to the measured data and the zero energy astrophysical S-factor for 3He( α , γ )7Be reaction was found to be 0.534 ± 0.025 keVb.

The Trojan Horse Method (THM) was applied to the p+d interaction in order to study the p+p scattering, the simplest case where the suppression of the Coulomb amplitude due to off-shell effects can be observed. The three-body p + d → p + p + n experiment was performed at 5 and 6 MeV and the shape of the quasi-free cross-section was investigated as a function of both the outgoing proton energy and the p-p relative energy. Preliminary results show a behaviour which turns out to be much similar to that of n+n, n+p and nuclear p+p cross-sections.

The 10B(p,α)7Be reaction is the main responsible for 10B destruction in stellar interior. In such environments this p-capture process occurs at a Gamow energy of ∼10 keV, and takes places mainly through a resonant state ( E x = 8.701 MeV ) of the compound 11C nucleus. Thus, a resonance right in the region of the Gamow peak is expected to significantly influence the behaviour of the astrophysical S(E)-factor. The 10B(p,α)7Be reaction has been investigated by means of the Trojan Horse Method (THM) applied to the 2H(10B,α7Be)n three-body process. The experiment was performed at E b e a m = 27 MeV at the Instituto de Fisica Nuclear de Sao Paulo. Preliminary results concerning the extraction of the bare-nucleus S(E)-factor will be presented.

Off-energy-shell effects in p-p scattering have been investigated at p-p relative energies from 600 down to 80 keV applying the Trojan horse method (THM) to the p+d{yields}p+p+n reaction at 5 MeV. In contrast with the on-energy-shell case, no Coulomb-nuclear interference minimum has been found in the extracted THM p-p cross section, due to the suppression of the Coulomb amplitude as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between THM p-p data and calculated on-energy-shell n+n, n+p and nuclear p+p cross sections.