2.1.4 Particle Interactions

Question 1

What are the four fundamental interactions

Answer 1

gravity
electromagnetic
weak nuclear
strong nuclear

Question 2

Define exchange particles

Answer 2

They are virtual particles that only exist for a short time - long enough to transfer energy, momentum, and other properties in the interaction. These exchange particles for the four fundamental forces are called gauge bosons.

Question 3

What is the exchange particle for the strong interaction?

Answer 3

Pions (π+, π0, π-)

They affect hadrons only.

Question 4

What is the exchange particle for the weak interaction?

Answer 4

W+, W- bosons

They affect all hypes of particles.

Question 5

What is the exchange particle for electromagnetic interactions?

Answer 5

Virtual photon

They affect charged particles only.

Question 6

What is the size of the exchange particle determined by?

Answer 6

The force - heavier exchange particles have a shorter range.

Question 7

Why can W bosons only exist for a short period of time?

Answer 7

They have a mass of about 100x of a proton giving the weak force a very short range.
Creating a W boson uses so much energy that it can only exist for a very short time.
Photon have virtually no mas so they have an infinite range.