Decays Caused by Weak and Strong Forces

The strong interaction and weak interaction can be compared in a set of particle decays which yield the same final products:

The extraordinary difference of 13 orders of magnitude in the lifetimes comes from the fact that the sigma decay does not conserve strangeness and therefore can proceed only by the weak interaction:

The lifetime of a decay is proportional to the inverse square of the coupling constant between the initial and final products, and since the final products are identical, the difference in lifetime must come from the difference in coupling constants. The coupling constant ratio can then be estimated for this situation:

Since the strong force coupling constant has a value around 1 in the energy range of these decays, we can estimate that the weak coupling constant has a value in the range:

Particle conservation laws

Particle concepts

Ch. 18
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