What is a longitudinally-polarized boson?

[touqra]

Occassionally, I come across this term: longitudinally-polarized boson. Does it mean that the boson spin is aligned with the x-axis ?

 

[Dick]

Longitudinal polarization is a relation between spin and momentum.

 

[touqra]

Longitudinal polarization is a relation between spin and momentum.

So, it means the spin and the momentum is aligned the same? Isn't this similar to helicity ?

 

[Dick]

I've always thought of them as the same. Is there a technical difference?

 

[Meir Achuz]

Longitudinally polarized means helicity equals zero.

 

[Dick]

Longitudinally polarized means helicity equals zero.

Thanks, Meir. I thought my memory seemed a little fuzzy on that.