1.7 Particle Interactions

Question 1

What are exchange particles?

Answer 1

Exchange particles are virtual particles that move between 2 interacting particles, bringing about a force between the particles.

Question 2

What are virtual particles?

Answer 2

Particles that only exist for a very short time

Question 3

What is the gauge boson of the strong force and what particles does the force affect?

Answer 3

• the pion
• affects hadrons only

Question 4

What is the gauge boson of the electromagnetic force and what particles does the force affect?

Answer 4

• photon
• affects charged particles only

Question 5

What is the gauge boson of the weak force and what particles does the force affect?

Answer 5

• W+ and W- bosons
• affects all types of particles

Question 6

What does the size of the exchange particle determine?

Answer 6

The range of the force. Heavier exchange particles have a shorter range

Question 7

What are the differences in range of the weak and electromagnetic force and what explains this?

Answer 7

• the weak force has a much shorter range than the electromagnetic force
• because W bosons have a mass of about 100x that of a photon

Question 8

How are different types of particles represented in Feynman diagrams?

Answer 8

• exchange particles are represented by wiggly lines
• other particles are represented by straight lines

Question 9

What are the rules for Feynman diagrams?

Answer 9

• incoming particles start at the bottom of the diagram and move upwards
• baryons stay on one side of the diagram and leptons stay on the other
• W bosons carry charge from one side of the diagram to the other (a W- particle going to the left has the same effect as a W+ particle going to the right)

Question 10

What is the gauge boson for beta minus decay?

Answer 10

W-

Question 11

What is the gauge boson for beta plus decay?

Answer 11

W+

Question 12

What is the equation for electron capture?

Answer 12

Proton + electron = neutron + electron neutrino

Question 13

What is the gauge boson for electron capture?

Answer 13

W+

Question 14

What is the equation for electron-proton collision?

Answer 14

The same as electron capture:
Proton + electron = neutron + electron neutrino

Question 15

What is the gauge boson for electron-proton collisions?

Answer 15

W-

Question 16

What is the exchange particle for electromagnetic repulsion?

Answer 16

Photon

Question 17

What is the equation for electromagnetic repulsion?

Answer 17

No particles are changed (electron -> electron etc)