SM: Leptons


Leptons in the standard model are defined as those fundamental particles which do not interact via the strong force. The strong force is one of the three fundamental forces in the standard model – the other two being electromagnetism and the weak force.

Leptons come in three different generations…


the electron, the muon and the tau and their associated neutrinos.

You may not have heard of neutrinos before but they are in fact all around is. They are created in the sun by a decay involving the weak force.


If you were to hold your thumb out then about 100 billion of neutrinos pass through it every second. You don’t feel it because neutrinos are very weakly interacting meaning they have to travel through a lot of stuff before having a sizeable probability of interacting. There is even an experiment in using part of the ice sheet of Antarctica to try and detect them – this experiment is affectionately called ICE CUBE.

Electrons are also worth a mention, since they pretty much determine the whole of chemistry. Most of the matter around us is made up of atoms…


… at the centre of which is a nucleus.  This nucleus is surrounded by electrons, held there by the electromagnetic force, and which in part determine the chemical properties of that atom.

If you don’t like reading….

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