New nuclear physics for big bang nucleosynthesis

Abstract

We discuss nuclear reactions which could play a role in Big Bang Nucleosynthesis (BBN). Most of these reactions involve lithium and beryllium isotopes and the rates for some of these have not previously been included in BBN calculations. Few of these reactions are well studied in the laboratory. We also discuss novel effects in these reactions, including thermal population of nuclear target states, resonant enhancement, and non-thermal neutron reaction products. We perform sensitivity studies which show that even given considerable nuclear physics uncertainties, most of these nuclear reactions have minimal leverage on the standard BBN abundance yields of 6 Li and 7 Li. Although a few have the potential to alter the yields significantly, we argue that this is unlikely.

Mirror matter can alleviate the cosmological lithium problem

“…First, the hypothesis underlying the standard computation and the stellar processes have all been reexamined carefully: (i) the nuclear reaction rates used in BBN calculations have been reexamined [41][42][43][44][45]; (ii) the possible depletion of 7 Li in stars has been discussed [46][47][48]; (iii) the temperature scale used in the 7 Li abundance determination has also been the subject of a lively debate [35,49]; and (iv) the 3-dimensional stellar modeling and non-local thermodynamical equilibrium effects have also been investigated but the results are not very different from those determined using 1-dimension models with local thermodynamical equilibrium [50].…”

The Primordial Lithium Problem

“…The effects of nonthermal daughter particles has been studied and found to be negligible (95,82). Plasma effects, and electron Coulomb screening are also unimportant (96).…”

“…Finally, the possibility of entirely new reactions has been recently studied by Boyd et al (82). These authors systematically considered a large set of reactions, some of which have been neglected in prior calculations.…”

“…Moreover, BBN calculations use a much more extended reaction network than the simplified view of Fig. 1, with all initial state pairings of A ≤ 7 species present but most practice unimportant (78,79,23,80,81,82,83). Thus, to change the primordial lithium predictions requires surprises of some kind-either (i) the cross sections the known important reactions have uncertainties far beyond the quoted errors, or (ii) the cross sections for normally unimportant reactions have been vastly underestimated.…”

Neutrino energy transport in weak decoupling and big bang nucleosynthesis

“…It has been argued that there is no nuclear physics fix for this problem (see for example Refs. [38,60] TABLE V: Changes in primordial abundances in BBN for Coulomb and radiative corrections. The first column gives the processes used for a given run.…”