7. Particle Interactions Flashcards
What are exchange particles?
Virtual particles that show how forces act between two particles
How long do virtual particles exist?
A short time, but long enough to transfer energy, momentum and other properties between particles in the interaction
What are the exchange particles for the four fundamental forces called?
Gauge bosons
Name the 4 fundamental interactions
- Strong
- Electromagnetic
- Weak
- Gravity
What are the gauge bosons for strong interactions?
Pions
What particles are affected by strong interactions?
Hadrons only
What are the gauge bosons for electromagnetic interactions?
Virtual photon (symbol ^)
What particles are affected by electromagnetic interactions?
Charged particles only
What are the gauge bosons for weak interactions?
W plus and W minus bosons
What particles are affected by the weak interactions?
All types
What determines the range of the force?
The size of the exchange particle
Why do weak forces have a short range?
The exchange particles are heavy
What are the rules for drawing Feynmann diagrams?
- Incoming particles start at the bottom of the diagram and move upwards (time points upwards)
- Baryons stay on one side, leptons on the other side
- The W bosons carry charge from one side of the diagram to the other (make sure charges are balanced)
- A W minus particle going to the left has the same effect as a W plus particle going to the right
What is electron capture?
When a proton-rich nucleus ‘captures’ an electron from inside the atom and change into a neutron and the W boson comes from the proton, making it W plus
What is the equation for electron capture?
Proton + electron → neutron + electron neutrino
