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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)].

For the first time the astrophysical factor of the $^{10}\mathrm{B}(p,{\ensuremath{\alpha}}_{0})^{7}\mathrm{Be}$ reaction has been measured over a wide energy range, from 5 keV to 1.5 MeV, via the Trojan horse method (THM) applied to the quasifree $^{2}\mathrm{H}(^{10}\mathrm{B},\ensuremath{\alpha}^{7}\mathrm{Be})n$ reaction. Therefore, the $S(E)$ factor has been recast into absolute units by scaling in the energy range 200 keV--1.2 MeV to a recent measurement using the activation method, leading to a normalization uncertainty of $4%$. An $R$-matrix fit of the THM data was performed, to parametrize the $S$ factor, obtain spectroscopic information on the populated resonances, and compare with other recent experiments. Finally, a new determination of the screening potential ${U}_{e}$ has been obtained, ${U}_{e}=240\ifmmode\pm\else\textpm\fi{}50$ eV, with a much smaller error than our previous measurement.

The reaction Ne-18(alpha, p)Na-21, of importance to nuclear astrophysics, has been studied directly using the postaccelerated radioactive Ne-18 beam available at Louvain-la-Neuve and a gaseous helium target. This: study covered the energy region from 2.04 to 3.01 MeV in the center of mass, and identified various levels in the compound nucleus Mg-22. The stellar reaction rate due to these states has been deduced. The experimental rate shows good agreement with theoretical predictions [J. Gorres, M. Wiescher, and F. K. Thielemann, Phys. Rev. C 51, 392 (1995)] above 2.5 GK. [S0556-2813(99)02906-4].

The reaction ${}^{17}\mathrm{O}(n,\ensuremath{\alpha}){}^{14}\mathrm{C}$ was studied at energies from ${E}_{\mathrm{c}.\mathrm{m}.}=0$ to ${E}_{\mathrm{c}.\mathrm{m}.}=350\phantom{\rule{0.28em}{0ex}}\mathrm{keV}$ by using the quasifree deuteron breakup in the three-body reaction ${}^{17}\mathrm{O}+d\ensuremath{\rightarrow}\ensuremath{\alpha}+{}^{14}\mathrm{C}+p$, which extended the Trojan Horse indirect method (THM) to neutron-induced reactions. It is found that the ${}^{18}\mathrm{O}$ excited state at ${E}^{*}=8.125\ifmmode\pm\else\textpm\fi{}0.002\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$, observed in THM experiments, is absent in the direct measurement because of its high centrifugal barrier. The angular distributions of the populated resonances have been measured by using this method. The results unambiguously indicate the ability of the THM to overcome the centrifugal barrier suppression effect and to pick out the contribution of the bare nuclear interaction.

This work has been supported by the Spanish MICINN under projects FPA2005-04460, FPA200502379, FPA2006-13807-c02-01, FPA2007-63074, FPA2009-07653, FPA2009-07387 and FPA2010 22131-C02-01, by the Junta de Andalucia project FQM-4964, by the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042) and Programme Multi-Dark (CSD2009-00064), by the European Community-Access to Research Infrastructure action of the Improving Human Potential Program Contract, No. HPRI-CT-1999-00110, and by the Belgian Program P5/07 on interuniversity attraction poles of the Belgian-state Federal Services for Scientific, Technical and Cultural Affairs. L. Acosta acknowledges financial support by the Universidad de Huelva.

The Trojan horse nucleus invariance for the binary reaction cross section extracted from the Trojan horse reaction was tested using the quasifree {sup 3}He({sup 6}Li,{alpha}{alpha})H and {sup 3}He({sup 7}Li,{alpha}{alpha}){sup 2}H reactions. The cross sections for the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He binary processes were extracted in the framework of the plane wave approximation. They are compared with direct behaviors as well as with cross sections extracted from previous indirect investigations of the same binary reactions using deuteron as the Trojan horse nucleus instead of {sup 3}He. The very good agreement confirms the applicability of the plane wave approximation which suggests the independence of the binary indirect cross section on the chosen Trojan horse nucleus, at least for the investigated cases.

The first results are reported on $(^{6}\mathrm{He},^{8}\mathrm{Be})$ two-proton pick-up reactions on $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, and $^{19}\mathrm{F}$ nuclei. The measurements were done with an $18\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ beam on $^{6}\mathrm{LiF}$, $^{7}\mathrm{LiF}$, $^{6}\mathrm{Li}_{2}\mathrm{C}{\mathrm{O}}_{3}$, and $^{12}\mathrm{C}$ targets. The measured angular distributions for the $^{12}\mathrm{C}(^{6}\mathrm{He},^{8}\mathrm{Be})^{10}\mathrm{Be}$ (g.s.) and $^{12}\mathrm{C}(^{6}\mathrm{He},^{8}\mathrm{Be})^{10}\mathrm{Be}^{*}(3.37\phantom{\rule{0.3em}{0ex}}\mathrm{MeV})$ reactions show a clear signature of a direct process. Although the contributions from the $^{6}\mathrm{Li}(^{6}\mathrm{He},^{8}\mathrm{Be})^{4}\mathrm{H}$ reaction were observed, no clear extraction of the $^{4}\mathrm{H}$ data was possible.

The reaction $^{6}\mathrm{He}+^{64}\mathrm{Zn}$ was studied in order to investigate the effects of the projectile neutron-halo structure on the reaction mechanism at energies around the Coulomb barrier. Elastic scattering angular distributions, transfer∕breakup angular distributions, and fusion excitation functions have been measured. Due to the low-recoil energy of the evaporation residues and the low intensity of the $^{6}\mathrm{He}$ beam, the fusion cross section was measured by detecting off-line the atomic x-ray emission which follows the electron capture decay of the evaporation residues. For comparison the reaction $^{4}\mathrm{He}+^{64}\mathrm{Zn}$ was studied using the same technique. The data for the reaction $^{6}\mathrm{He}+^{64}\mathrm{Zn}$ show that the transfer and breakup mechanisms account for almost $80%$ of the total reaction cross section, moreover we do not observe an enhancement of the fusion cross section when compared with the $^{4}\mathrm{He}+^{64}\mathrm{Zn}$ reaction.

V. Z. Goldberg et al. ; 10 pags.; 10 figs.; 2 tabs. ; PACS number(s): 21.10.2k, 24.30.2v, 27.30.1t

For the first time Borromean nucleus induced reactions have been measured below the three-body breakup threshold. A set of angular distributions for the single and two neutron transfer as well as on the charge exchange reaction channel has been obtained. The experimental data have sufficient angular coverage and precision to allow for the discrimination between different model predictions, which do not suffer from ambiguities introduced to the interpretation of experimental data due to flux losses into the three-body breakup channel. The viability of the idea is demonstrated in the case of nuclear reactions induced by the simplest Borromean nucleus, i.e., He-6, on a structureless target, i.e., protons. Comparison with different theoretical approaches suggest that coupled channel effects play an important role. A decrease of the model wave function's rms radius of 0.15 fm alters the predicted angular distributions such that they no longer follow the experimental results.

A new measurement of the 18F(p,α) reaction and the 18F(p,p) elastic scattering was performed at the Radioactive Ion Beam facility in Louvain-la-Neuve. Values were deduced for the resonance energy, total width, partial width, and resonance strength of the 7.07 MeV level in 19Ne, confirming and increasing the precision of a first result obtained several years ago in the same lab.

Information on the Li-7(p,alpha)He-4 reaction cross section at energies relevant for astrophysics has been obtained by means of the indirect Trojan-horse method applied to the three-body H-2(Li-7, alpha alpha)n reaction. Measurements at Li-7-beam energies of 19, 19.5, 20, and 21 MeV have been carried out. The results are reported in terms of the astrophysical S(E) factor. The value S(0) measured in the present experiment is compared with that extrapolated from a direct measurement. [S0556-2813(99)01510-1].