Study of Primordial Deuterium Abundance in Big Bang Nucleosynthesis

Big Bang nucleosynthesis (BBN) theory predicts the primordial abundances of the light elements 2H (referred to as deuterium, or D for short), 3He, 4He, and 7Li produced in the early universe. Among these, deuterium, the first nuclide produced by BBN, is a key primordial material for subsequent reactions. To date, the uncertainty in predicted deuterium abundance (D/H) remains larger than the observational precision. In this study, the Monte Carlo simulation code PRIMAT was used to investigate the sensitivity of 11 important BBN reactions to deuterium abundance. We found that the reaction rate uncertainties of the four reactions d(d, n)3He, d(d, p)t, d(p, γ)3He, and p(n, γ)d had the largest influence on the calculated D/H uncertainty. Currently, the calculated D/H uncertainty cannot reach observational precision even with the recent LUNA precise d(p, γ)3He rate. From the nuclear physics aspect, there is still room to largely reduce the reaction-rate uncertainties; hence, further measurements of the important reactions involved in BBN are still necessary. A photodisintegration experiment will be conducted at the Shanghai Laser Electron Gamma Source (SLEGS) Facility to precisely study the deuterium production reaction of p(n, γ)d.