📘 Particle Physics: Modern Physics

What you’ll learn

1. Historical Emergence of the Standard ModelTrace the experimental milestones that assembled the Standard Model from 1930s cosmic-ray work through the 1970s gauge-theory synthesis.The chapter reviews key discoveries that fixed the particle content and force carriers. It highlights how parity violation and neutral currents forced electroweak unification. Students leave with a timeline of the gauge group SU(3)×SU(2)×U(1) and its empirical anchors.
2. Quantum Field Theory PreliminariesApply canonical quantization and path-integral methods to free scalar and Dirac fields at the level required for interacting theories.Students derive the propagator for massive vector bosons and confront the need for gauge fixing. The discussion covers normal ordering, Wick’s theorem, and the origin of ultraviolet divergences. Emphasis falls on why renormalization becomes unavoidable even before interactions.
3. Quarks, Color, and QCDCalculate one-loop beta functions and explain confinement versus asymptotic freedom using the running coupling.The lesson derives the QCD beta function and discusses the scale Λ_QCD. It examines how color factors produce the linear potential between static quarks. Edge cases include the heavy-quark potential and lattice determinations of the string tension.
4. Leptons and Weak Charged CurrentsConstruct the charged-current Lagrangian and compute tree-level cross sections for muon decay and inverse beta decay.Students evaluate helicity amplitudes and confront the V-A structure. The chapter quantifies the suppression of right-handed currents and introduces CKM mixing for hadronic decays. Precision observables such as the Michel parameters receive brief attention.
5. Electroweak Unification and Neutral CurrentsDerive the Weinberg angle from spontaneous symmetry breaking and compute neutral-current couplings.The lesson walks through the Higgs doublet vev and the resulting gauge-boson mass matrix. It calculates forward-backward asymmetries at the Z pole and discusses oblique corrections. Trade-offs between on-shell and MS-bar renormalization schemes are examined.
6. Feynman Rules and Higher-Order CorrectionsTranslate Feynman diagrams into amplitudes for QED and electroweak processes at one-loop order.Students practice dimensional regularization on the photon self-energy and vertex correction. The chapter isolates infrared and ultraviolet divergences and shows how they cancel in inclusive observables. Renormalization-group improvement of predictions is introduced.
7. Accelerators and Detector SystemsEvaluate luminosity, pile-up, and tracking resolution requirements for Higgs and beyond-Standard-Model searches.The lesson compares synchrotron radiation limits in lepton versus hadron colliders. It details silicon pixel granularity needed for b-tagging and calorimeter compensation for jet energy scale. Trade-offs between trigger bandwidth and offline reconstruction are quantified.
8. The Higgs Boson Discovery and PropertiesExtract Higgs couplings from production and decay rates and test custodial symmetry.Students compute partial widths in the Standard Model and compare them with measured signal strengths. The chapter examines the tensor structure of the hVV vertex and limits on invisible decays. Current precision on the top-Yukawa coupling via ttH is reviewed.
9. Neutrino Mass and OscillationsConstruct the PMNS matrix and compute oscillation probabilities in vacuum and matter.The lesson derives the two-flavor survival probability and introduces the MSW resonance condition. It discusses absolute mass limits from tritium beta decay and neutrinoless double-beta decay. Sterile-neutrino anomalies and their tension with cosmology are noted.
10. CP Violation and BaryogenesisCalculate the Jarlskog invariant and assess whether Standard-Model CP violation suffices for baryogenesis.Students evaluate the size of the baryon asymmetry generated by sphalerons and Sakharov conditions. The chapter contrasts the CKM phase with potential new sources in the neutrino sector. Limitations of the Standard Model for explaining the observed η_B are quantified.
11. Supersymmetry and NaturalnessWrite the MSSM superpotential and soft-breaking terms and compute the lightest Higgs mass at one loop.The lesson examines the μ problem and fine-tuning measures. It compares gaugino unification predictions with current LHC limits. Compressed spectra and R-parity violation as escape routes receive attention.
12. Dark Matter CandidatesDerive the Boltzmann equation solution for freeze-out and map direct-detection limits onto parameter space.Students compare WIMP, axion, and sterile-neutrino candidates. The chapter evaluates spin-independent scattering rates and the neutrino floor. Mono-jet and disappearing-track signatures at colliders are contrasted with underground experiments.
13. Early-Universe Particle PhysicsCompute freeze-out abundances for weakly interacting particles and assess entropy injection effects.The lesson links the QCD phase transition temperature to the baryon-to-photon ratio. It examines gravitino and moduli problems in supersymmetric cosmologies. Constraints from CMB spectral distortions on late decays are reviewed.
14. Future Facilities and Outstanding QuestionsEvaluate the physics reach of proposed Higgs factories and 100 TeV hadron colliders for Standard-Model precision and new-physics searches.Students compare luminosity and energy trade-offs across linear and circular designs. The chapter flags open questions in flavor, neutrino mass, and the hierarchy problem that remain after HL-LHC. Prospects for axion-like particles and dark photons at beam-dump experiments close the course.

Questions this course answers

Grounded in trusted sources

• OpenStax University Physics
• Fermi National Accelerator Laboratory
• CERN

Every Wunder lesson is built from real, reputable sources — never invented.

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