Classifying interactions by force

[Identity]

What are the general features you should look for when classifying an arbitrary particle interaction according to strong, weak, or electromagnetic forces? Cheers

 

[AdrianTheRock]

This was the problem that faced nuclear physicists in the early/middle part of the last century, not yet knowing for sure exactly what fundamental interactions there were. In looking at spontaneous reactions, they found that two main clues were

1. the kinds of products produced by the decays, and
2. the decay rates/widths, or particle lifetimes.

Examples of (1) are the fact that all electromagnetic interactions involve - and, usually, emit - photons, and that any reaction which emits a neutrino (or antinuetrino) is a weak interaction.

For short-lived subatomic particles such as mesons, the lifetime of the particle also gives a good indication of the force involved, eg

π⁺ → μ⁺ v : τ ≈ 2 x 10^-8 s → weak interaction​

π⁰ → γ γ : τ ≈ 10^-16 s → electromagnetic interaction​

ρ⁰ → π⁺ π^- : τ ≈ 10^-23 s → strong interaction.​

 

[Identity]

Great answer Adrian, thanks :)