Nuclear reaction rates and primordial6Li

Abstract

We examine the possibility that Big Bang Nucleosynthesis (BBN) may produce non-trivial amounts of 6 Li. If a primordial component of this isotope could be observed, it would provide a new fundamental test of Big-Bang cosmology, as well as new constraints on the baryon density of the universe. At present, however, theoretical predictions of the primordial 6 Li abundance are extremely uncertain due to difficulties in both theoretical estimates and experimental determinations of the 2 H(α, γ) 6 Li radiative capture reaction cross-section. We also argue that present observational capabilities do not yet allow the detection of primeval 6 Li in very metal-poor stars of the galactic halo. However, if the critical cross section is towards the upper end of its plausible range, then improvements in 6 Li detection capabilities may allow the establishment of 6 Li as another product of BBN. It is also noted that a primordial 6 Li detection could help resolve current concerns about the extragalactic D/H determination. 26.35.+c,26.44.+h,25.90.+k

New nuclear physics for big bang nucleosynthesis

“…Nollett et al [31] have provided an insightful and comprehensive study of the nuclear reactions which bear on 6 Li production and destruction, while Cyburt and Pospelov [32] have explored the necessary issues for a pure nuclear physics solution to the 7 Li overproduction problem. In this paper we explore related issues, find no clear paths to solution of either lithium problem, but do provide rates for incorporation into BBN codes as well as studies of the sensitivity of lithium isotope production and destruction to uncertainties in these rates.…”

Neutron Spectroscopic Factors of 7 Li and Astrophysical 6 Li(n,γ) 7 Li Reaction Rates

“…In addition, due to the difference between the depletion speeds of 6 Li and 7 Li in stars, the 6 Li/ 7 Li ratio could stand for a measure of the time scale for stellar evolution. In the above scenario, 6 Li(n,γ) 7 Li is believed to be one of the important reactions in the SBBN network [4,5], its reaction rates would affect the abundances of both 6 Li and 7 Li.The cross sections of 6 Li(n,γ) 7 Li at astrophysically relevant energies are most likely dominated by the E1 transitions into the ground and first exited states in 7 Li. To date, only one direct measurement of the 6 Li(n,γ) 7 Li cross sections at stellar energies has been performed [6].…”

6Li/7Li estimates for metal-poor stars

“…Their derived abundances in metal-poor stars are difficult to reconcile simultaneously with standard predictions. Different production sites in the early Galaxy have been discussed: Big Bang nucleosynthesis (Wagoner et al 1967;Nollett et al 1997;Coc et al 2004;Jedamzik 2008), cosmic ray spallation and/or α-fusion (Reeves et al 1970;Vangioni-Flam et al 2000) and neutrino spallation (see e.g. Vangioni-Flam et al 1996).…”