Classification of particles

Hadrons are subject to the strong interaction.

The two classes of hadrons:

• baryons (proton, neutron) and antibaryons (antiproton and antineutron)

• mesons (pion, kaon).

Baryon number as a quantum number.

Conservation of baryon number.

The proton is the only stable baryon into which other baryons eventually decay.

The pion as the exchange particle of the strong nuclear force.

The kaon as a particle that can decay into pions.

Leptons: electron, muon, neutrino (electron and muon types only) and their antiparticles.

Lepton number as a quantum number; conservation of lepton number for muon leptons and for electron leptons.

The muon as a particle that decays into an electron.

Strange particles

Strange particles as particles that are produced through the strong interaction and decay through the weak interaction (eg kaons).

Strangeness (symbol s) as a quantum number to reflect the fact that strange particles are always created in pairs.

Conservation of strangeness in strong interactions.

Strangeness can change by 0, +1 or -1 in weak interactions.

Appreciation that particle physics relies on the collaborative efforts of large teams of scientists and engineers to validate new knowledge.