Indirect determination of the astrophysical S factor for the Li6(p,γ)Be7 reaction using the asymptotic normalization coefficient method

G. G. Kiss et al.
Phys. Rev. C 104, 015807 – Published 29 July 2021

Abstract

Background: The Li6(p,γ)Be7 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 Li6(He3,d)Be7 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 He3 beam impinging on a Li6 target was Elab=3 MeV and Elab=5 MeV. The yield of the emitted deuterons was measured with high precision by using silicon ΔEE telescopes.

Results: From the DWBA analysis of the angular distributions of the emitted deuterons populating the ground (E*=0.0 MeV; 32) and the first excited (E*=0.429MeV; 12) states of Be7, the ANCs for the Li6+pBe7 system were deduced. Furthermore, the recently measured Li6(p,γ)Be7 reaction cross sections [Piatti et al., 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 Li6(p,γ)Be7 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 et al. [Phys. Rev. C 102, 052802 (2020)], Dong et al. [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 et al. [Phys. Lett. B 725, 287 (2013)] and Xu et al. [Nucl. Phys. A 918, 61 (2013)].

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  • Received 21 January 2021
  • Revised 14 April 2021
  • Accepted 29 June 2021

DOI:https://doi.org/10.1103/PhysRevC.104.015807

©2021 American Physical Society

Physics Subject Headings (PhySH)

Nuclear PhysicsGravitation, Cosmology & Astrophysics

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Vol. 104, Iss. 1 — July 2021

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