Nucleon Mass Corrections to the $p\leftrightarrow n$ Rates During Big Bang Nucleosynthesis

Abstract

The thermal rates for converting neutrons to protons, and vice versa, are calculated, including corrections of order 1 MeV divided by a nucleon mass. The results imply that the primodial helium abundance predicted for big bang nucleosynthesis has been systematically underestimated by about $\delta Y_4=0.0012$, i.e., $\delta Y_4/Y_4\approx .005$.

Comments: 32 pages (Latex)