How long do fundamental particles last?

25 November 2012

Question

Dear  Dr. Smith,

How long do protons and neutrons survive outside an atom?

Salih

Answer

Martin - Protons and electrons, as far as we're concerned in our lifetime last forever.

Neutrons last for just under 15 minutes if they're on their own. To do an experiment, actually the experiments we do with neutron scattering take place where you only need for them to last for less than a second. So that's not an issue. But you can actually capture neutrons, put them in something like a little bottle. They last for just under 15 minutes. If you have a neutron that's actually part of a nucleus then it effectively lasts forever. But on its own, just under 15 minutes.

Dave - So being inside that nucleus is somehow stabilising it, making it last a lifetime.

Martin - Yes, absolutely.

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