Particle Physics and Cosmology

sources:

• text: Halliday, Resnick, Walker - Fundamentals of Physics

1. The Standard Model
2. Conservation Laws and Symmetries
3. Feynman Diagrams
4. The Higgs Mechanism
5. Group Theory in Particle Physics
6. Running Coupling Constants
7. Big Bang Cosmology
8. Neutrino Physics
9. Beyond the Standard Model
10. Problem Set
11. Advanced Topics in Particle Physics
12. Advanced Topics in Cosmology
13. Precision Tests of the Standard Model

University-level particle physics and cosmology notes covering the Standard Model, Feynman diagrams, and cosmology.

• Standard Model: Quarks, leptons, gauge bosons, Higgs mechanism. The Standard Model classifies all known fundamental particles and describes three of the four fundamental forces (electromagnetic, weak, strong).
• Feynman Diagrams: Rules, calculations, cross sections, decay rates. Feynman diagrams are pictorial representations of particle interactions that encode mathematical expressions.
• Symmetries: Conservation laws, gauge invariance, spontaneous symmetry breaking. Every conservation law corresponds to a symmetry (Noether’s theorem), and gauge symmetries dictate the form of interactions.
• Cosmology: Big bang, inflation, dark matter, dark energy. Cosmology connects particle physics to the large-scale universe, tracing how the early universe cooled through phase transitions.

• Quantum mechanics (operators, perturbation theory)
• Electromagnetism (Maxwell”s equations, gauge invariance)
• Special relativity (four-vectors, Lorentz transformations)
• Statistical mechanics (thermal physics, thermodynamics)

Start with the Standard Model to understand the foundations, then progress to Feynman diagrams and cosmology. Each section includes worked examples and practice problems.

Use the sidebar to browse topics, or start with the introductory pages linked from the sidebar.

Each section includes:

• Detailed explanations of key concepts
• Worked examples with step-by-step solutions
• Practice problems with answers
• Common pitfalls and how to avoid them
• Connections to other areas of physics

Particle physics seeks to identify the fundamental building blocks of matter and the forces governing their interactions. The Standard Model organises these into quarks, leptons, and gauge bosons, with the Higgs mechanism explaining how particles acquire mass. Feynman diagrams translate abstract quantum field theory calculations into intuitive pictures of particle collisions and decays. Symmetries are central: every conservation law corresponds to a symmetry via Noether’s theorem, and gauge symmetries dictate the form of interactions. Cosmology connects particle physics to the large-scale universe, tracing how the hot, dense early universe cooled through phase transitions that froze out the particles and forces we observe today.

1. Master the Standard Model: Understand the particles and their interactions
2. Practise Feynman diagrams: Learn the rules and draw many diagrams
3. Learn symmetries: Understand the connection between symmetries and conservation laws
4. Follow experiments: Keep up with recent discoveries at CERN and other facilities
5. Connect to cosmology: Relate particle physics to the early universe

• Quantum Mechanics: Quantum field theory foundations.

• Classical Mechanics: Gravitational theory in cosmology.

• Thermal Physics: Thermodynamics of the early universe.

• Calculus

• Linear Algebra

• Vector Calculus

• Quantum Computing

• Confusing quarks with leptons: Quarks interact via all four fundamental forces and are confined inside hadrons; leptons (electrons, neutrinos) do not participate in the strong force. An electron is not made of quarks.
• Assuming antimatter has negative mass: Antimatter has positive mass and positive energy. It differs from matter in quantum numbers (charge, lepton number), not in gravitational behaviour. Antimatter falls down, not up.
• Ignoring conservation laws in Feynman diagrams: Every vertex must conserve charge, lepton number, baryon number, and colour charge. Drawing diagrams that violate these rules produces physically impossible processes.
• Treating the Higgs field as the source of all mass: The Higgs mechanism gives mass to W and Z bosons and to fundamental fermions. Most of the proton’s mass comes from QCD binding energy, not from the Higgs field.