How to identify bound or resonance states? Say we got a peak in our scattering experiment, how do we decide whether that peak is a resonance or a bound state?
Edit : Say in a LHCb experiment we discover a new particle.
 A: Normally a new bound state  in a single force universe would not decay into other particles, so  a resonance would be declared if an enhancement is observed since the invariant mass of particles exceeds the sum of the masses of the constituents.
In particle physics, when measuring the invariant mass of a group of particles and observe an enhancement , we treat it as a possible new particle , even though the invariant mass of the enhancement is bigger than the mass of the sum of the constituents. The reason is that there are three forces involved in the standard model modeling particle interactions, and the mathematical structure allows what are elementary particles for one force to decay due to the other forces into other particles.
Take the electron positron scattering  crossection:

The standard model fits the enhancements up to the Z with its group structure for particle combinations so the term resonance fits, but Z is an elementary particle in the standard model ,  and the fact its decay has a width is due to experimental errors  and to the number of interactions contributing to the decay .
New resonances are sought in the LHC experiments that would not fit  in the group structure of the current standard model , asking for extensions or new models that predict other group structures. Elaborate models ask for leptoquarks, for  example this link.
