# Are there notable cases of anomalies in the mass-decay rate relationship?

As a general rule of thumb, massive particles (both composite and fundamental) tend to decay rapidly through the weak force, while less massive particles tend to be more stable. Hence, taus are shorter lived than muons, top quarks are shorter lived than charm quarks, and all mesons and baryons except protons and neutrons are highly unstable. My understanding is that this relationship is largely captured in the Standard Model electro-weak equations.

Are there any notable cases where the decay rate and the mass of the particle appear experimentally to deviate from the expected relationship?

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 an interesting extension to your question - shouldn't we expect there to be islands of stability for hadron spectra? i'm referring to the analogy with heavy nuclei – lurscher Mar 16 '11 at 20:03

Second, all the decays you mention use the weak force and the elementary Feynman diagram is always the same: it's a cubic vertex with one W-boson, one decaying fermion, and one fermionic decay product. So the amplitude is essentially $g_{SU(2)} \bar u_{final} \gamma_\mu u_{initial} \epsilon_W^\mu$.
However, what hugely depends on the mass of the fermions are the kinematic factors - the Lorentz-invariant phase space, if you wish. The "universal" amplitude above has to be integrated over all allowed momenta of the final particles, with the $d^3 p / 2E$ measure. Also, there's $1/2E$ for each initial particle.