Particle Types Overview
The Standard Model Particles
The Standard Model contains 17 fundamental particles organized by their properties.
Fermions (Spin 1/2)
Fermions are matter particles obeying Fermi-Dirac statistics and the Pauli exclusion principle.
Quarks
| Generation | Up-type | Down-type |
|---|---|---|
| 1st | up (u) | down (d) |
| 2nd | charm (c) | strange (s) |
| 3rd | top (t) | bottom (b) |
Properties:
- Carry color charge (strong interaction)
- Carry electric charge (+2/3 or -1/3)
- Never observed in isolation (confinement)
Leptons
| Generation | Charged | Neutrino |
|---|---|---|
| 1st | electron (e^-) | \nu_e |
| 2nd | muon (\mu^-) | \nu_\mu |
| 3rd | tau (\tau^-) | \nu_\tau |
Properties:
- No color charge (no strong interaction)
- Neutrinos have very small mass
Bosons (Integer Spin)
Bosons are force carriers obeying Bose-Einstein statistics.
Gauge Bosons (Spin 1)
| Boson | Force | Couples to |
|---|---|---|
| Photon (\gamma) | Electromagnetic | Electric charge |
| Gluon (g) | Strong | Color charge |
| W^\pm | Weak | Weak isospin |
| Z^0 | Weak | Weak isospin |
Higgs Boson (Spin 0)
- Gives mass to W^\pm, Z^0, and fermions
- Discovered at CERN in 2012
- Only fundamental scalar in the Standard Model
Mathematical Representations
Gauge Group Structure
The Standard Model gauge group is:
G_{SM} = SU(3)_C \times SU(2)_L \times U(1)_Y
| Subgroup | Force | Bosons |
|---|---|---|
| SU(3)_C | Strong | 8 gluons |
| SU(2)_L | Weak | W^1, W^2, W^3 |
| U(1)_Y | Hypercharge | B |
After electroweak symmetry breaking:
- W^{1,2} \to W^\pm
- W^3, B \to Z^0, \gamma
Representations of Fermions
Fermions transform under specific representations:
| Particle | SU(3)_C | SU(2)_L | U(1)_Y |
|---|---|---|---|
| Left quark doublet | 3 | 2 | +1/6 |
| Right up quark | 3 | 1 | +2/3 |
| Right down quark | 3 | 1 | -1/3 |
| Left lepton doublet | 1 | 2 | -1/2 |
| Right electron | 1 | 1 | -1 |
Beyond the Standard Model
Particles not in the Standard Model but theorized:
- Graviton: Spin-2 carrier of gravity
- Dark matter candidates: WIMPs, axions
- Supersymmetric partners: Squarks, sleptons, gauginos
References
- D. J. Griffiths, Introduction to Elementary Particles, 2nd ed. (Wiley-VCH, 2008)
- M. Thomson, Modern Particle Physics (Cambridge University Press, 2013)
- Particle Data Group — Comprehensive particle physics data
- CERN: The Standard Model — Introduction to particle physics
- M. E. Peskin and D. V. Schroeder, An Introduction to Quantum Field Theory (Westview Press, 1995), Chapter 1
- A. Zee, Quantum Field Theory in a Nutshell, 2nd ed. (Princeton University Press, 2010)