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 1?

  • 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

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
  • 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?

  • A𝛾̄𝑣e+e+2+
  • B𝜏𝜏𝛾2𝑣++
  • C146147CN+e
  • D158157+ON+e
  • E𝜏𝜇̄+v+v

Q9:

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

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, e+e𝛾.

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.

𝜏𝜇𝜈+

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.

np+e+ve

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

  • A+2
  • B+3
  • C+1
  • D0
  • E1

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

  • A1
  • B0
  • C1
  • D3
  • E2

Q13:

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

𝜇̄𝑣e++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?

  • A𝜇̄𝜈𝜈e++e
  • B𝛾𝜇𝜇+
  • C146147CN+e
  • D𝜏𝜏𝛾+
  • E158157eON+e+𝜈

Q15:

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

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

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

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