Introduction

Why Particle Physics?

Particle physics is the study of the most fundamental constituents of matter and the forces that govern them. It is the deepest layer of physical reality we have access to — quarks, leptons, and the bosons that mediate the electromagnetic, weak, and strong forces, all unified in the Standard Model.

Every collision at the LHC, every neutrino that passes through the Earth, every decay of a muon is governed by the equations you will implement in this course. Particle physics gave us the Higgs boson, quantum electrodynamics (the most precisely tested theory in science), and the prediction that there are exactly three families of matter particles.

This course implements the core equations of particle physics in pure Python. No libraries — just the mathematics of special relativity, quantum field theory, and experimental particle physics expressed as functions. Each lesson introduces one formula, explains the physics, and asks you to write it as code.

You will implement:

• Relativistic kinematics — invariant mass, center-of-mass energy, threshold energies
• Particle decays — decay widths, branching ratios, lab frame decay lengths
• Scattering — Rutherford cross sections, Breit-Wigner resonances, the fine structure constant
• Standard Model — the Weinberg angle, running couplings, the Higgs mechanism

Let's start with natural units.