Hadrons are particles made up of quarks held together by the strong nuclear force. Protons and neutrons are hadrons.

Neutrons are not used in the LHC because they decay when they are not bound within atomic nuclei. Protons are stable even outside atomic nuclei.

The image, right, shows a proton made up of two ‘up’ quarks and one ‘down’ quark.

The grey circle and black squiggles represent the strong nuclear force holding the quarks together.