- #1
Soph_the_Oaf
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Hi there
Iive been reading the intro chapter to Peskin and Schroder's 'An intro to QFT'
I have a question regarding the conservation of angular momentum during particle collisions/scatterings
As an example they talk about e+ e- --> μ+ μ-
The take the Centre of Mass (CM) frame.
Consider the case where
e+ is right handed and moving in + z-direction
e- is left handed and moving in negative z-direction.
This gives us a total of + one unit of angular momentum in the z direction
These then couple to a photon which has polarisation vector (0,1, i,0)
- this is circularly polarised in the z direction
- is has angular momentum of plus one in z direction
Then we look at the muons
these may have a polarization (0, cosθ, i, -sinθ) where θ is the scattering angle
- so the muons have a total angular momentum of +1 in the direction that is rotated by θ from the z direction
So I am confused how this conserved angular moment
- at the start we had +1 in the z-direction
- now we have +1 in the direction at angle θ to the z direction
Can anyone explain this to me please. Is it to do with the reference frame somehow?
Thanks
Soph
Iive been reading the intro chapter to Peskin and Schroder's 'An intro to QFT'
I have a question regarding the conservation of angular momentum during particle collisions/scatterings
As an example they talk about e+ e- --> μ+ μ-
The take the Centre of Mass (CM) frame.
Consider the case where
e+ is right handed and moving in + z-direction
e- is left handed and moving in negative z-direction.
This gives us a total of + one unit of angular momentum in the z direction
These then couple to a photon which has polarisation vector (0,1, i,0)
- this is circularly polarised in the z direction
- is has angular momentum of plus one in z direction
Then we look at the muons
these may have a polarization (0, cosθ, i, -sinθ) where θ is the scattering angle
- so the muons have a total angular momentum of +1 in the direction that is rotated by θ from the z direction
So I am confused how this conserved angular moment
- at the start we had +1 in the z-direction
- now we have +1 in the direction at angle θ to the z direction
Can anyone explain this to me please. Is it to do with the reference frame somehow?
Thanks
Soph