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

¹ Laboratori Nazionali del Sud INFN, Via S. Sofia 62, 95123 Catania, Italy
² Institute for Nuclear Research (ATOMKI), H-4001 Debrecen, POB.51, Hungary
³ Institute of Nuclear Physics, Uzbekistan Academy of Sciences, 100214 Tashkent, Uzbekistan
⁴ Physical and Mathematical Department, Gulistan State University, 120100 Gulistan, Uzbekistan
⁵ Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
⁶ Dipartimento di Fisica e Astronomia “E. Majorana”, Università di Catania, 95123 Catania, Italy
⁷ Jožef Stefan Institute, Department of Low and Medium Energy Physics (F2), 1000 Ljubljana, Slovenia
⁸ Nuclear Physics Institute of the Czech Academy of Sciences, 250 68 Rˇ ež, Czech Republic
⁹ Facoltà di Ingegneria e Architettura, Università di Enna “Kore”, 94100, Enna, Italy
¹⁰ Center for Nuclear Study (CNS), University of Tokyo, RIKEN campus, Saitama 351-0198, Japan
¹¹ Centro Siciliano di Fisica Nucleare e Struttura della Materia (CSFNSM), Catania 95123, Italy
¹² Dipartimento di Fisica e Geologia, Università di Perugia, 06123 Perugia, Italy
¹³ Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, 06123 Perugia, Italy
¹⁴ National Research Center “Kurchatov Institute”, Moscow 123182, Russia
¹⁵ Cyclotron Institute, Texas A&M University, College Station, Texas 77843, USA

^* e-mail: lacognata@lns.infn.it

Published online: 22 March 2023

Abstract

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.