Well, there is clearly a hierarchy of importance of particles, although I don't know a very clear cut criterion (other than being "interesting"). Protons and n

Well, there is clearly a hierarchy of importance of particles, although I don't know a very clear cut criterion (other than being "interesting"). Protons and neutrons are clearly important, but excited states thereof (e.g. N(1440), N(1520), etc., see http://pdg8.lbl.gov/rpp2014v1/pdgLive/ParticleGroup.action?node=BXXX005 http://pdg8.lbl.gov/rpp2014v1/pdgLive/ParticleGroup.action?n...) are clearly less so. Their masses and quantum numbers obviously tell us something about how baryons work, but nobody will get too excited about N(XXXX).