Excited hadrons v. fundamental particles

[ohwilleke]

Mesons and baryons have both a ground state and excited states involving the same valence quarks but a higher mass (which can in principle be calculated from QCD).

Fundamental fermions and bosons, however, do not appear to display this behavior. They have a ground state, and while there are three "generations" of fermions, there are not the infinite number of excited states of fermions that there are of hadrons, and there are no excited states of fundamental bosons.

Is there a reason in the math and equations of HEP that this is the case?

 

[ChrisVer]

hmm... That there's nothing to excite ? (non-composite)
Mesons have excitations because bound states with different angular momenta are possible.