Before we look at the fundamental laws that govern all particle interactions…

We’re going to take a look at a couple more important examples of particle interactions. 

Ones that are particularly common inside particle accelerators… and frequently come up in exams. 

To kick off, we’ve seen several examples of nuclear decays. 

However, these aren’t the only type of decay that can occur. 

For instance, muons are super unstable particles. 

So unstable in fact, that on average they only tend to stick around for around 2 microseconds before they decay into a handful of other particles. 

This decay is a result of the weak force. 

And it leads to a muon decaying into an electron, an electron antineutrino and a regular muon neutrino 

Now, just like nuclear decays, we can write an equation to represent this particle interaction 

Which is…

This equation represents the decay of a muon into an electron, a muon neutrino and an electron antineutrino.

Next, the muon’s antiparticle – the antimuon – is also super unstable, and also decays into a bunch of different particles very quickly. 

This time, those particles are the positron, an electron neutrino and a muon antineutrino. 

Which we can represent with a particle equation…

This equation shows an antimuon decaying into a positron, a muon antineutrino and an electron neutrino.

The interaction is a result of the weak force. 

And if we compare it to a standard muon decay 

…line them up like this. 

Then we can see that each particle here has its corresponding antiparticle here. 

Finally, as we’ve now seen, it’s not just the nucleus of an atom that can decay, 

Muons and antimuons are examples of particles that also decay. 

So when we’re talking about a nucleus decaying, we call the process nuclear decay.

Whereas when we’re talking about any particle decaying, we just call the process particle decay.

Meaning nuclear decay is one type of particle decay.

And a muon decay is another example of a particle decay. 

To sum up, whenever a particle turns into other particles, we call the process…

Whenever a particle decays into other particles, we call the process particle decay. 

For instance, a muon decays into…

A muon decays into an electron, a muon neutrino and an electron antineutrino 

And these muons decay due to the weak force. 

Whereas, an antimuon decays into…

An antimuon decays into a positron, a muon antineutrino and an electron neutrino

And these antimuons decay due to the weak force.