Nuclear and Particle Physics: Classification of Particles

Particle Classification

All particles in the Universe can be classified into two categories: hadrons and leptons.

Hadrons

Two key types of hadrons: baryons and mesons.
Baryons are made up of three quarks; protons and neutrons are examples of baryons.
Mesons are made up of a quark and an antiquark; pions and kaons are examples of mesons.
Hadrons are subject to the strong nuclear force.

Leptons

Leptons are fundamental particles that are not subject to the strong nuclear force.
Six types of leptons: electron, muon, tau, electron-neutrino, muon-neutrino, tau-neutrino.
Each lepton has a corresponding antiparticle.
Leptons have a half integer spin and are subject to the weak nuclear force.

The Charge of Particles

Quarks can have a charge of -1/3 or +2/3.
Leptons can have a charge of -1, 0, +1.

Bosons

Bosons are particles that carry forces.
Four types of bosons: photon (electromagnetic force), W & Z bosons (weak nuclear force), gluon (strong nuclear force) and the Higgs boson.
Graviton is a theoretical boson for the force of gravity, but it is not yet proven to exist.

Colour Charge

Quarks have an attribute called colour charge, which is related to the strong nuclear force.
Colour charge can be red, green or blue and anti-quarks have anti-red, anti-green or anti-blue.
All hadrons are colour-neutral, meaning the sum of their colour charges adds up to white or zero.

This concludes the general classification of particles in nuclear and particle physics. For a detailed overview of quark flavours, baryon and meson families, and properties of specific particles, please refer to the corresponding sections of your revision materials.