Submitted by sosodank t3_yf0kz3 in askscience
i understand that the uud structure of the proton is the lowest allowed energy state of three quarks, and thus it can't decay (supersymmetric theories aside). the neutron, meanwhile, is udd and can (when by itself, or in the right kind of nucleus) undergo beta decay to a proton via spontaneous emission of a massive, charged W boson.
furthermore, i understand that for instance non-spontaneous fission occurs when a neutron of sufficient energy interacts with the nucleus, bringing it to an unstable energy level. u235 is close to this level, and thus fissions when interacting with a neutron of even thermal energy, whereas u238 needs a higher-energy neutron to fission. high-energy photons can furthermore knock nucleons out in photodisintegration.
2.78MeV differentiate the up and down quark. This energy ought be readily available; the excited Ni60 metastate decays with a 1.33MeV γ, about half this value. Why don't we see protons transmuting to neutrons when such gamma rays hit them, especially in e.g. a plasma where there are no electrons to get in the way (at nuclear distance scales)?
sorry, i am merely a dumb computer scientist.
[deleted] t1_iu134d2 wrote
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