4-Vectors and Particle Mass

Time and space ­coordinates vary depending on the frame of reference in which a collision event is measured. 4-­vectors are tools that can simplify the transformations between frames of reference.

Conservation Laws

These laws govern the reactions we observe in particle physics! Their violation would be a sign of new physics.

Cross Section and Luminosity

This sheet defines cross section and luminosity, presents examples of LHC cross sections, and introduces the method used to determine number of events.

Feynman Diagrams

A powerful tool to visually represent particle interactions, as well as to conduct elaborate calculations! Learn the basics on how to read Feynman diagrams.

Monte Carlo Simulation

Monte Carlo (MC) methods help ATLAS physicists simulate data by generating theoretical collisions based on both known and theorised physics. We use the simulated data to help us understand the detector’s behaviour, optimise algorithms, and identify new physics.

Particle Decay, Lifetime & Width

The lifetime (or equivalently, the width) and the different ways elementary particles can decay are fundamental properties crucial for physicists exploring the boundaries of known physics.

Signal and Background

This sheet defines signal and background and presents some common strategies for increasing the signal-to-background ratio.

Statistical Significance

When physicists make statements about whether or not a given process has been observed in the LHC data, they must back up their claim with strong statistical evidence. This is often expressed in terms of standard deviations or the p-value.

The Standard Model

All fundamental particles classified based on their properties! Deviations to the Standard Model can point the way to new physics.