# Worksheet: Feynman Diagrams

In this worksheet, we will practice interpreting Feynman diagrams and determining which interactions are possible using Feynman diagrams.

Q1:

Which of the following Feynman diagrams shows a muon decaying into an electron and two neutrinos via the weak interaction?

• A • B • C • D Q2:

Is the interaction shown in the Feynman diagram possible? If not, why not? • ANo, because it doesn’t conserve baryon number
• BNo, because it doesn’t conserve electric charge
• CNo, because it doesn’t conserve lepton number
• DYes
• ENo, because it doesn’t conserve energy

Q3:

The Feynman diagram shows a neutron undergoing beta decay. What particle is represented by in the diagram? • A
• B
• C
• D
• E

Q4:

The Feynman diagram is supposed to show the annihilation of an electron and a positron to produce a gamma-ray photon and then the pair production of an electron and a positron by that same photon. However, the diagram has been drawn incorrectly. Which of the following statements correctly describes how the diagram is incorrect? Time goes from left to right in the diagram. • AThe photon line should be drawn at an angle to show its movement through space.
• BThe arrows for the electron lines have been drawn in the wrong direction. The lines for particles with negative electric charge should point backward in time.
• CThe arrows for the positron lines have been drawn in the wrong direction. Antiparticle lines should point backward in time.
• DThere is no arrow on the line for a photon.
• EThe photon should be represented by a straight, dashed line rather than a sinusoidal line.

Q5:

The Feynman diagram shows an up quark in a proton that collides at high speed with another proton. The up quark emits a gluon, which then produces a down quark–antiquark pair. How many virtual particles are shown in the diagram? Q6:

Which of the following Feynman diagrams shows the interaction ?

• A • B • C • D Q7:

Which of the following Feynman diagrams shows the annihilation of an electron and a positron to produce a gamma-ray photon?

• A • B • C • D Q8:

What phenomenon does the Feynman diagram show? The -axis represents time. • AElectron–positron annihilation
• BElectron–positron pair production
• C decay
• D decay
• EElectromagnetic attraction between an up quark and an electron

Q9:

What particle phenomenon does the Feynman diagram show? The -axis represents time. • AElectron–positron pair production
• BElectromagnetic repulsion between two electrons
• CAbsorption of a photon by an electron
• DEmission of a photon by an electron
• EElectron–positron annihilation

Q10:

What particle phenomenon does the Feynman diagram show? The -axis represents time. • AElectron–positron annihilation
• BElectromagnetic attraction between an electron and a positron
• CAbsorption of a photon by an electron
• DEmission of a photon by an electron
• EElectron–positron pair production

Q11:

What particle phenomenon does the Feynman diagram show? The -axis represents time. • AEmission of a photon by an electron
• BElectromagnetic attraction between an electron and a positron
• CAbsorption of a photon by an electron
• DElectron–positron annihilation
• EElectron–positron pair production