I'm working through BBN theory with Dodelson and other papers. I have a question about the reactions between particles in the $1\space MeV$ range. We have reactions that produce and annihilate protons and neutrons during this epoch, so where is the treatment for anti-protons and anti-neutrons? Isn't the universe creating and destroying anti-protons and anti-neutrons during this same time? Won't the anti-protons and protons react during this epoch to produce photons? Won't high-energy photons collide and produce protons and anti-protons?
Yes, I know about the hand-waving argument that we're just going to pretend there's some asymmetry between matter and anti-matter and jam in a free parameter which is the baryon-photon ratio at the onset of nucleosynthesis, but that doesn't address the fact that anti-protons should be created under the same conditions as protons. It appears that the abundance of any given species of particle at a given time depends on accounting for every possible reaction. I don't understand the justification for leaving out what appears to me to be the most important reaction of the $1\space MeV$ temperature range.