# Exploring The Universe With LHC Glossary

Important definitions and theorems relevant to special relativity & particle physics

## A #

### Atlas #

One of the primary detectors at CERN. It was responsible for finding the Higgs boson in 2012, and plays a crucial role in looking for dark matter.

## C #

### Cherenkov Radiation #

A type of radiation which charged particles emit when they travel faster than light in a medium.

## D #

### Dark Matter #

Something that has gravity, and something that doesn't radiate. We know it exists because the rotation curve of the milky way doesn't decay outwards while the distribution of gas and stars decays exponentially outward.

## F #

### Four Vector #

A convinient way of handling the three spatial plus one time dimension in a single vector.

### Fundamental Postulates Of Special Relativity (Axioms) #

1. The speed of light in vacuum is constant in all reference frames. 2. All intertial systems are equivalent.

_{Synonyms: Axioms}

## I #

### Intertial System (Inertial frame of reference) #

A reference system on which no forces act, so there is no acceleration.

_{Synonyms: Inertial frame of reference, Inertial reference frame, Inertial space}

## L #

### Lorentz Factor (/$\gamma/$) #

A linear factor with which length, time, and relativistic mass change for a moving object. /$$ \gamma = \frac{1}{\sqrt{1-\frac{v^2}{c^2}}}/$$

_{Synonyms: /$\gamma/$}

### Lorentz Transformation #

A linear transformation which is used to transform between different intertial systems.

Read more about Lorentz Transformation.

## M #

### Machos #

A possible, but unlikely explanation of dark matter invplving planets, dwarf stars, and black holes. However, it can only account for 10% of dark matter. WIMPs are a better explanation.

## P #

### Pseudorapidity (/$\eta/$) #

/$$ \eta = -\ln \big( \tan \big( \frac{\theta}{2} \big) \big) /$$

_{Synonyms: /$\eta/$}

## S #

### Standard Configuration #

The standard configuration consists of an rest system /$S/$ with coordinates /$(x,y)/$, and another system /$S'/$ with coordinates /$(x',y')/$ moving with /$v/$ along the /$x/$-axis with respect to /$S/$. Furthermore, at /$t=0/$, we set /$x=x'=0/$.

## T #

### Transition Radiation #

A type of radiation which fast charged particles emit when they cross the boundary of two insulators with different resistances.

## W #

### Wimps (Weakly interacting massive particles) #

A likely explanation of dark matter which predicts a new invisible particle type flying with /$10^6 \frac{\text{km}}{\text{h}}/$ everywhere. These particles have never been observed, but could feasibly be detected in ATLAS.

_{Synonyms: Weakly interacting massive particles}