# How is each neutrino associated with a specific charged lepton?

For instance, why is an electron neutrino called that and what is its relationship with an electron?

Lepton neutrino and corresponding lepton carry specific lepton charge which is approximately conserved in all SM interactions. This means that corresponding lagrangian contains symmetry - invariance under simultaneous transformations $$e_{L/R}\to e^{i\alpha}e_{L/R}, \quad \nu_{L} \to e^{i\alpha}\nu_{R}$$ Due to chiral character of electron-neutrino interaction, this means that electron and neutrino form the doublet, $$L_{e} = \begin{pmatrix} e_{L}\\ \nu_{L}\end{pmatrix}$$

The short version is that simply assign the neutrino flavors according to the flavor of charged lepton they are associated with.

This is clearest in the context of quasi-elastic scattering. When we see a reaction like $$\nu + n \longrightarrow l^- + p^+ \,,$$ we simple say, "Oh, that neutrino has the same flavor as the lepton we see in the final state. This identification is exactly what Name YYY means when he says they "form a doublet".

• also beta decay, where the neutrino had to be invented to conserve energy and electron number. – anna v Mar 8 '16 at 6:18

There are 3 classes of leptons : electrons , muons and tau-leptons ; each class with more mass than the preceding one.

Neutrinos only interact via the Weak-Nuclear force. In this interaction apart from the usual energy, momentum and angular momentum; lepton number is conserved.

The different classes of lepton only interact with their own kind of neutrino. Each class has a different ± lepton number.

I have no idea how this is detected experimentally, the top 2 classes being quite rare, and neutrino detection being even rarer.