# 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

- AMuon, electron antineutrino, and tauon
- BAntitauon, tauon, and tau neutrino
- CTau neutrino, electron antineutrino, and tauon
- DAntitauon, tauon, and tau antineutrino
- 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

- AMu antineutrino, positron, and electron antineutrino
- BPositron, electron neutrino, and mu neutrino
- CMu antineutrino, electron, and positron
- DPositron, electron neutrino, and electron
- EElectron neutrino, mu neutrino, 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

- ATau antineutrino, electron antineutrino, and proton
- BPhoton, tau neutrino, and neutron
- CElectron antineutrino, proton, and antimuon
- DProton, antimuon, and antitauon
- EPhoton, proton, and neutron

**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+2
- B+3
- C+1
- D0
- E

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

- A
- B0
- C1
- D3
- 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

**Q15: **

The following equation shows a tauon decaying into a muon, a tau neutrino, and a mu antineutrino,

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

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