AcademyParticles and Cosmology
Academy
Standard Model
Level 1 - Physics topic page in Particles and Cosmology.
Principle
The Standard Model organizes matter into quarks and leptons, and interactions into exchange bosons. It explains a wide range of particle data but does not include every known feature of the universe.
Notation
\(q\)
quark
\(\ell\)
charged lepton
\(\nu\)
neutrino
\(\gamma\)
photon
\(W^\pm,Z^0\)
weak bosons
\(H\)
Higgs boson
Method
Derivation 1: Matter particles are fermions
Fermions are grouped in three generations. Ordinary matter mostly uses first-generation particles.
First generation
\[u,d,e^-,\nu_e\]
Higher generations
\[\mu,\tau,c,s,t,b\]
Derivation 2: Interactions use bosons
Each interaction in the Standard Model has associated exchange particles.
Electromagnetic
\[\gamma\]
Weak
\[W^\pm,Z^0\]
Strong
\[g\]
Derivation 3: Conservation laws test reactions
Allowed particle processes must satisfy exact conservation laws such as charge and energy-momentum conservation.
Charge conservation
\[\sum Q_i=\sum Q_f\]
Energy-momentum conservation
\[p_i^\mu=p_f^\mu\]
Rules
Charge conservation
\[\sum Q_i=\sum Q_f\]
First generation
\[u,d,e^-,\nu_e\]
Weak bosons
\[W^\pm,\ Z^0\]
Examples
Question
Classify an electron in the Standard Model.
Answer
An electron is a first-generation charged lepton.
Checks
- Quarks and leptons are matter fermions.
- Photons, gluons, and weak bosons are interaction bosons.
- The Higgs field is associated with elementary-particle masses.
- The Standard Model is powerful but incomplete.