The Underground Nuclear Astrophysics in the Precision Era of BBN: Present Results and Future Perspectives

Abstract

The abundance of light isotopes such as D, 3He, 4He, 6Li and 7Li produced during Big Bang Nucleosynthesis (BBN) only depends on particle physics, baryon density and relevant nuclear processes. At BBN energies (0.01 ÷ 1 MeV) the cross section of many BBN processes is very low because of the Coulomb repulsion between the interacting nuclei. As low-energy measurements on earth's surface are predominantly hampered by the effects of cosmic rays in the detectors, it is convenient to study the relevant reactions with facilities operating deep underground. Starting from the present uncertainty of the relevant parameters in BBN (i.e. baryon density, observed abundance of isotopes and nuclear cross-sections), it will be shown that the study of several reactions of the BBN chain, with existing or proposed underground accelerator facilities, can improve the accuracy of BBN calculations, providing a powerful tool to constrain astrophysics, cosmology and particle physics. In particular, a precise measurement of D(p, γ)3He reaction at BBN energies is of primary importance to calculate the baryon density of universe with an accuracy similar to the one obtained by Cosmic Microwave Background (CMB) experiments, and to constrain the number of active neutrino species. For what concern the so called ’’Lithium problems”, i.e. the disagreement between computed and observed abundances of the 7Li and 6Li isotopes, it will be also shown the importance of a renewed study of the D(α, γ) 6Li reaction.