Worksheet: Units for Particle Rest Masses

In this worksheet, we will practice using units of eV/c² to express the masses of subatomic particles and converting between eV/c² and kg.

Q1:

ParticleElectronMuonTauon
Mass511/𝑐keV106/𝑐MeV1.78/𝑐GeV

The table shows the masses of the three charged leptons. What is the most massive lepton–antilepton pair that could be produced via pair production from a 150 MeV photon?

  • AA tauon–antitauon pair
  • BA muon–antimuon pair
  • CAn electron–positron pair

Q2:

What is 4.99×10 kg in keV/𝑐? Give your answer to 3 significant figures.

Q3:

A muon has a mass of 106/𝑐MeV. What is the mass of a muon in kilograms? Give your answer to 3 significant figures.

  • A1.89×10 kg
  • B1.89×10 kg
  • C6.32×10 kg
  • D1.69×10 kg
  • E1.69×10 kg

Q4:

The Feynman diagram shows a sigma baryon decaying into a neutron and a pion.

What particle is represented by 𝑋 in the diagram?

  • A𝑊
  • B̄𝑠
  • C̄𝑑
  • D𝑊
  • E𝑑

What particle is represented by 𝑌 in the diagram?

  • Ā𝑠
  • B𝑊
  • C𝑊
  • D𝑑
  • Ē𝑑

Q5:

The Feynman diagram shows an antitauon decaying into an antimuon. What particle is represented by 𝑋 in the diagram?

  • A𝑊
  • B𝛾
  • C𝑊
  • D𝜇
  • E𝑔

Q6:

Is the interaction shown in the Feynman diagram possible? If not, why not?

  • ANo, because a W boson cannot decay into a pion
  • BNo, because it doesn’t conserve strangeness
  • CNo, because it doesn’t conserve the baryon number
  • DNo, because it doesn’t conserve electric charge
  • EYes

Q7:

Which of the following Feynman diagrams shows the interaction 𝜏𝜇𝜈𝜈––++ ?

  • A
  • B
  • C
  • D

Q8:

Which of the following equations represents the Feynman diagram shown?

  • AΣ𝜋n+
  • BΣ𝜋n++W–
  • CΣ𝜋n+
  • DΣ𝜋n++W+
  • EΣ𝜋n+

Q9:

Which of the following equations represents the Feynman diagram shown?

  • Adu++𝜇𝜈
  • Bu+d2𝜇
  • C𝜋𝜇𝜈+
  • Ddu+e+𝜈
  • Eud++𝜇𝜈

Q10:

The Feynman diagram shows a lambda baryon decaying into a proton and a pion. What particle is represented by X in the diagram?

  • Ad
  • Bu
  • Cu
  • Ds
  • Ed

Q11:

The Feynman diagram shows a down quark decaying into an up quark, producing a W boson, which decays into an electron and an electron antineutrino. Which of the particles shown in the diagram is a virtual particle?

  • A𝜈e
  • Bd
  • Ce
  • Du
  • EW

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