3. The Weak Force Flashcards
What are the two types of the weak force?
The Charged current and the neutral current
What is the mediator of the charged current, and what is the rough mass?
W+- boson
- mass = 80GeV
What is the mediator of the neural current, and what is the rough mass?
Z0 boson
- mass = 91GeV
Why is the probability of the weak interaction so small?
Because at low q^2 (4 momentum of the probe/photon) the probability is proportional to α_W / (M_W) ^4
- 4th power of a very large mass
What is the coupling factor of the weak force equal to?
sqrt(α_W) = 1/26
- x5 stronger than sqrt(EM) = 1/137
When is the probability of the weak interaction very strong?
When q^2 is nearly = to M_W^2
α_W / [q^2 - (M_W) ^4]
How many generations of particles are there and what are they?
3
Leptons, hadrons, neutrinos
How is the Z0 used to determine the number of generation of particles?
It can decay into all generations of a particle and corresponding antiparticle
How many neutrino generations are there?
3 from the Z0 decay
What is the weak charge also called?
Weak isospin = T_3
What is the weak isospin for the top and bottom of a doublet?
+1/2 at the top
-1/2 at the bottom
Give an example of a doublet in SM
ν_e T_3(ν_e) = 1/2
e -1/2
What is the weak isospin of the W+- boson?
W+ = +1 W- = -1
Where is weak isospin conserved on the FD?
At the vertex
How are the W+- and Z0 particles different in terms of isospin and the doublets?
Z0 has T_3 = 0
- W+- can couple top particles to bottom particles in the doublet
