The Standard Model of Particle Physics
• Jane Doe
Overview
The Standard Model (SM) is the theoretical framework that describes three of the four fundamental forces—electromagnetism, the weak nuclear force, and the strong nuclear force—and classifies all known elementary particles.
Fundamental Particles
Particles are grouped into two families:
- Fermions—the building blocks of matter. They come in three generations of quarks and leptons.
- Gauge Bosons—the carriers of the forces. Photons mediate electromagnetism, W and Z bosons mediate the weak force, and gluons mediate the strong force.
Key Equations
The Lagrangian of the Standard Model encodes its dynamics:
L_SM = -¼ F_{μν}F^{μν} + i \barψγ^μD_μψ - ½ (∂_μϕ)(∂^μϕ) - V(ϕ) + …where F_{μν} is the field strength tensor, ψ denotes fermion fields, ϕ the Higgs field, and V(ϕ) its potential.
Experimental Successes
From the discovery of the W and Z bosons in the 1980s to the Higgs boson’s observation in 2012, the SM has withstood countless experimental tests.
Limitations and Open Questions
Despite its successes, the SM does not explain:
- Gravity
- Dark matter and dark energy
- Neutrino masses (without extensions)
- The matter‑antimatter asymmetry
These gaps motivate the search for physics beyond the Standard Model (BSM).
Further Reading
For a deeper dive, see the reviews by the Particle Data Group and recent lectures from the CERN summer school.