Nuclear weak interaction rates in primordial nucleosynthesis

Abstract

We calculate the weak interaction rates of selected light nuclei during the epoch of big bang nucleosynthesis (BBN), and we assess the impact of these rates on nuclear abundance flow histories and on final light element abundance yields. We consider electron and electron antineutrino captures on $^{3}\mathrm{He}$ and $^{7}\mathrm{Be}$, and the reverse processes of positron capture and electron neutrino capture on $^{3}\mathrm{H}$ and $^{7}\mathrm{Li}$. We also compute the rates of positron and electron neutrino capture on $^{6}\mathrm{He}$. We calculate beta and positron decay transitions where appropriate. As expected, the final standard BBN abundance yields are little affected by addition of these weak processes, though there can be slight alterations of nuclear flow histories. However, nonstandard BBN scenarios, e.g., those involving out of equilibrium particle decay with energetic final state neutrinos, may be affected by these processes.