# What is muon relaxation?

## What is muon relaxation?

Longitudinal Field Muon Spin Relaxation (LF-μSR) involves the application of an external magnetic field parallel to the initial direction of the muon spin polarization. Here one measures the time evolution of the muon polarization along its original direction.

Does a muon have spin?

A muon is a spin-1/2 particle. A particle physicist would think of a positive muon as a lepton, a heavy anti-electron. This is because its spin can Larmor precess in the local magnetic field. Muons live only for 2.2 us (on average!)

### What is the spin of a muon?

The muon (/ˈmjuːɒn/; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 e and a spin of 1/2, but with a much greater mass. It is classified as a lepton.

What is the mass of a muon?

muon mass
Numerical value 1.883 531 627 x 10-28 kg
Standard uncertainty 0.000 000 042 x 10-28 kg
Relative standard uncertainty 2.2 x 10-8
Concise form 1.883 531 627(42) x 10-28 kg

## How was positron discovered?

Carl David Anderson discovered the positron on 2 August 1932, for which he won the Nobel Prize for Physics in 1936. The positron was the first evidence of antimatter and was discovered when Anderson allowed cosmic rays to pass through a cloud chamber and a lead plate.

Do muons have strangeness?

The muon family number is Lμ = 0 before and Lμ = −1+1 = 0 after. Strangeness changes from +1 before to 0 + 0 after, for an allowed change of 1. The decay is allowed by all these measures.

### How are muons detected?

Typical muon detectors consist of photomultiplying tubes lined with a scintillator, a material that emits light when struck by a charged particle. When a particle such as a muon bounces through the detector, the photomultiplying tube multiplies the current produced by the emitted light.

What is spin polarized current?

Spin polarization is the degree to which the spin, i.e., the intrinsic angular momentum of elementary particles, is aligned with a given direction. This property may pertain to the spin, hence to the magnetic moment, of conduction electrons in ferromagnetic metals, such as iron, giving rise to spin-polarized currents.

## How far do muons travel?

Muons are created when cosmic rays traveling through space strike molecules in the atmosphere, some 10 kilometers above Earth’s surface. Even moving at nearly the speed of light, a muon should only be able to travel about 700 meters before it decays, so you might think no muons could ever reach Earth.

How are muons made?

Muons are everywhere Muons have the same negative charge as electrons but 200 times the mass. They are made when high-energy particles called cosmic rays slam into atoms in Earth’s atmosphere. Travelling at close to the speed of light, muons shower Earth from all angles.

### Where was positron discovered?

In 1932 Carl Anderson, a young professor at the California Institute of Technology in the US, was studying showers of cosmic particles in a cloud chamber and saw a track left by “something positively charged, and with the same mass as an electron”.