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Does the strong (nuclear) force ever contribute to decay ? Or is the weak nuclear force the only decaying force ?

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Yes. The clearest example of strong-mediated decay would be alpha decay, but there are a lot of examples. – Jerry Schirmer Oct 22 '12 at 13:48
Is that explained somewhere well ? Wiki ? – mick Oct 22 '12 at 13:49
How much physics background do you have? At the popular level, nuclear binding energy is mostly determined by the strong force. Anything that has its energy production governed by that is going to be mostly strong-mediated. – Jerry Schirmer Oct 22 '12 at 13:52
The OP asked whether the strong force "contributes" to decay. I'm not sure I'd interpret the strong force as contributing to alpha decay. As the alpha tunnels out, it's feeling both strong and electrical forces. The strong force is attractive, so if anything, it's hindering the decay. The reason there's a big release of energy (which is why alpha decay happens so frequently in nature) is the electrical force. – Ben Crowell May 3 '13 at 0:58

Most of the resonances detected in particle physics scattering experiments are bound states of the strong force, bound for a time interval before decay .

These are created in the interaction and seen in invariant mass combinations of the interaction products, statistically.

The distinction with electromagnetic or weak decays comes from the widths of the resonances: the strong decays have MeV widths, whereas weak and electromagnetic decays are at the experimental error.Tables of delta resonances and N resonances etc can be found in the particle data booklet.

lamda strong

Here the invariant mass of a proton K pair shows a lamda resonance induced by the strong force.

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