# Worksheet: The Conservation of Lepton Number

In this worksheet, we will practice determining the total lepton number of a set of particles and whether given interactions conserve lepton number.

**Q1: **

What is the lepton number of a mu neutrino?

**Q2: **

Which of the following particles have a lepton number of 1?

- muon
- antitauon
- tau Neutrino
- electron antineutrino
- tauon
- tau antineutrino

- AAntitauon, tauon, and tau antineutrino
- BAntitauon, tauon, and tau neutrino
- CMuon, electron antineutrino, and tauon
- DTau neutrino, electron antineutrino, and tauon
- EMuon, tauon, and tau neutrino

**Q3: **

Which of the following particles have a lepton number of ?

- mu antineutrino
- electron
- positron
- electron neutrino
- mu neutrino
- electron antineutrino

- APositron, electron neutrino, and electron
- BPositron, electron neutrino, and mu neutrino
- CElectron neutrino, mu neutrino, and electron antineutrino
- DMu antineutrino, electron, and positron
- EMu antineutrino, positron, and electron antineutrino

**Q5: **

What is the lepton number of an antitauon?

**Q6: **

What is the lepton number of an electron antineutrino?

**Q7: **

Which of the following particles have a lepton number of 0?

- electron neutrino
- tau antineutrino
- electron antineutrino
- proton
- antimuon
- antitauon
- photon
- tau neutrino
- neutron

- APhoton, proton, and neutron
- BElectron antineutrino, proton, and antimuon
- CTau antineutrino, electron antineutrino, and proton
- DPhoton, tau neutrino, and neutron
- EProton, antimuon, and antitauon

**Q8: **

Which of the following equations shows a particle interaction that would not violate the conservation of lepton number?

- A
- B
- C
- D
- E

**Q9: **

The following equation shows a muon and an antimuon being produced via pair production from a gamma-ray photon,

What is the total lepton number before the interaction takes place?

What is the total lepton number after the interaction takes place?

**Q10: **

The following equation shows an electron and a positron annihilating to produce a gamma-ray photon,

What is the total lepton number before the interaction takes place?

What is the total lepton number after the interaction takes place?

**Q11: **

The following equation shows a particle interaction that is not possible because it violates the conservation of lepton number.

What is the total lepton number before the interaction takes place?

What is the total lepton number after the interaction takes place?

**Q12: **

The following equation shows a particle interaction that is **not** possible because it violates the conservation of lepton
number.

What is the total lepton number before the interaction takes place?

- A+1
- B
- C+2
- D+3
- E0

What is the total lepton number after the interaction takes place?

- A3
- B0
- C1
- D
- E2

**Q13: **

The following equation shows an antimuon decaying into an antielectron, a mu antineutrino, and an electron neutrino.

What is the total lepton number before the interaction takes place?

What is the total lepton number after the interaction takes place?

**Q14: **

Which of the following equations shows a particle interaction that would violate the conservation of lepton number?

- A
- B
- C
- D
- E