Does the mass difference between p+ and e+ explain differences wrt e- ?

[nomadreid]

My question is best explained by a Gedankenexperiment. First we have a hydrogen atom, with the electron not collapsing into the nucleus for the well-known reason of its minimum energy being above that needed to overcome the Coulomb force. Fine. Now replace the proton in the nucleus with a positron. Blip! the electron and positron annihilate. But the Coulomb forces are the same, the electron's energy is still quantised, so why doesn't the same mechanism work?

[Meir Achuz]

The electron wave function does not vanish at the origin so the electron does have a finite probability of being at the location of the proton. They do not annihilate because they are not antiparticles.

[nomadreid]

Thank you, Meir Achuz. I had not considered this aspect. That puts a new light on the problem.

[BHamilton]

The effect you're talking about does contribute in positronium: in some sense it helps explain why positronium should live so long (0.1 ns). This is enormous in the sense that it is larger than the lifetime of some neutral mesons which can only decay through the weak force. (I'm thinking of the K short here).

If the electron and positron are spin aligned, you actually can have it live even longer: on the order of 100 ns

[nomadreid]

BHamilton: thank you for that information; it is very interesting and enlightening.