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 1 ?

  • 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

Q4:

What is the lepton number of an electron?

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 𝛾 ̄ 𝑣 e + e + 2 +
  • B 1 5 8 1 5 7 + O N + e
  • C 𝜏 𝜇 ̄ + v + v
  • D 1 4 6 1 4 7 C N + e
  • E 𝜏 𝜏 𝛾 2 𝑣 + +

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.

𝜏 𝜇 𝜈 +

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 1
  • C+2
  • D+3
  • E0

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

  • A3
  • B0
  • C1
  • D 1
  • E2

Q13:

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

𝜇 ̄ 𝑣 e + + v + e

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 1 4 6 1 4 7 C N + e
  • B 1 5 8 1 5 7 e O N + e + 𝜈
  • C 𝜏 𝜏 𝛾 +
  • D 𝛾 𝜇 𝜇 +
  • E 𝜇 ̄ 𝜈 𝜈 e + + e

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