Under what conditions can a positron exist in everyday conditions?

Question

I am still learning basic quantum field theory and I am curious in what circumstances could a positron exist as a stable particle like an electron or proton, say for example in a human body or a marble? I have the impression that it is unstable and has the tendency to annhilate with an electron rather quickly, but in QM everything is probabilities, so there must be a nonzero probability it can survive? What would it have to do to accomplish this?

Asher · Answer

A positron is stable, just as an electron is stable. Neither one decays into other particles; an electron or positron on its own will survive forever.

The hard part is getting a positron "on its own" anywhere. There are electrons pretty much everywhere in the universe, even in interstellar and intergalactic space, and since electrons and positrons are oppositely charged its very difficult to keep them separated. When they meet, they tend to annihilate.

So there's really only one difficult condition to positron survival: don't let it touch anything.

Under what conditions can a positron exist in everyday conditions?

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