by Maxim Khlopov on Wed 11 Jan 2012 19:23
Dear Roman,
In your case equilibrium n/p ratio is supported by pion charge exchange reactions.
I don't think that there is any difference between such reactions for positively and negatively charged pions.
Your charged pions are stable, while neutral pions are unstable.
When temperature falls down below the mass of pions, charged pions freeeze out and there is no way to convert protons in neutrons and vice versa. Therefore freezing out of pions leads to freezing out of n/p ratio, which is (at the pion freezing out temperature - please find it) with the high accuracy equal 1.
For charged pions their frezing out is determined by their electromagnetic annihilation to photons or electron-positron pairs.
Regards
M.Yu.Khlopov
[i]Хлопов Максим Юрьевич
Maxim Khlopov[/i]