1. Leptons At Work

2. Research Task - Homework
some questions to research:
What is a positron?
Who suggested it must exist?
Who discovered it?
What is a muon?
When was it discovered?
Who said, ‘Who ordered that?’
What is a neutrino?

3. Today’s Objectives To learn about lepton conservation rules
Start practicing questions!

4. Recap Baryon Number and Lepton Number Practice
Particle Classification Exercise - What Am I?

5. Leptons
There are six particle-antiparticle pairs known.  Leptons (Greek – “light thing” or “small coins”) are the smallest of the fundamental particles.  They have the following properties:
fundamental particles without structure
they interact by the weak interaction.  If they are charged, they interact by the electromagnetic interaction, but NOT the strong interaction.

6. Leptons Leptons come in a family of three:
electron electron neutrino lightest
muon muon neutrino ↓
tauon tauon neutrino heaviest
Note that each has a corresponding neutrino.

7. Worksheet
 Conservation of Q, B & L sheet.

8. Muon Decay
This happens:-
What about this:-
Why?

9. The names of the leptons are:
Lepton Name
Lepton Symbol
Charge
Lepton Number
electron e-
-1e
Le = 1, Lμ= 0, Lτ = 0
electron neutrino νe
muon μ-
Le= 0, Lμ = 1, Lτ = 0
muon-neutrino νμ
tau τ-
Le = 0, Lμ= 0, Lτ = 1
tau neutrino ντ

10. Do these happen?
Conservation of Lepton Type Sheet

11. Lepton Notes
charge and lepton number are conserved in all allowed lepton processes.
There are three categories of lepton number, Le, Lμ, and Lτ.  Each lepton has a lepton number, 0 or 1, in each category, and each antilepton has a number 0 or -1 in each category.  You need to know the lepton numbers.

12. Lepton Notes Each particle has an antiparticle;
for the electron, it is the positron,
the muon the antimuon,
and the tau, the antitau. 
We show the anti-particle either by an opposite charge (e+) or by putting a bar across the symbol.