HADRON

hadron

(noun) any elementary particle that interacts strongly with other particles

Source: WordNet® 3.1

Etymology

Noun

hadron (plural hadrons)

(particle) A composite particle that comprises two or more quarks held together by the strong force and (consequently) can interact with other particles via said force; a meson or a baryon.

Usage notes

• Aside from individual quarks (which are never observed by themselves) hadrons are the only particles that interact via the strong force. Thus, a possible (though potentially slightly misleading) definition is "composite particle that can interact via the strong force" - or indeed simply "composite particle", as all hadrons are composite and all known non-hadrons are not known to be composite. Either definition however will be non-marginally wrong if the existence of the hypothetical "glueballs", non-hadronic composite particles consisting of gluons, is confirmed.

• The two categorisations hadron versus non-hadron and fermion versus boson together turn out to comprise a useful high-level categorisation of subatomic particles. (See the diagram above.)

(Missing from the diagram are quarks, the building blocks of hadrons. They are elementary, and therefore not themselves hadrons; they are, however, fermions. Thus, they would be classified, alongside leptons, as non-hadronic fermions.)