Why heavy bosons are unstable? I'm​ working with dark matter and in the some of concepts is that shall exist WIMPs (weakly interacting massive particles) in which are made by baryons... However, we know that this cannot satisfy the feature of stability in such model. One of consequences is that WIMPs cannot be made by baryonic particles because of its instability. 
Thus, I wanna know the why heavy baryons are unstable. I'm deeply thankful with any help :)
 A: The general idea is that all particles are unstable unless there's a conservation law preventing them from decaying into something lighter. Anything that is not forbidden is mandatory!
The main relevant (at least approximate) conservation laws are baryon number, lepton number, and charge. So the lightest baryon (the proton), the lightest lepton (the neutrino), and the lightest charged particle (the electron) are all stable. Some nuclei are stable as well, since they are lighter than any other combination of particles with the same charge and baryon number.
Any heavier baryon can always decay into a proton and other stuff (mesons, typically) without violating any conservation laws. And so they do.
As an aside, many theories predict the proton is unstable too, but at very, very long time scales. Like $10^{34}~\rm years$ or more.
Many new theories beyond the standard model come with new conservation laws, and so there may be more stable particles. For instance, in some models the lightest supersymmetric particle would be stable and fairly non-interacting, and so a viable dark matter candidate.
