QM: Neutrino Polarization - Oscillation & Mass Polarization

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Discussion Overview

The discussion revolves around the polarization of neutrinos and its relation to oscillation and mass. Participants explore the concepts of particle spin, polarization states of various particles, and the implications of mass on these properties.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes that neutrinos are described as "essentially left handedly polarized" and questions what is oscillating if neutrinos can be polarized.
  • Another participant asserts that polarization does not require oscillation, as particles can possess intrinsic angular momentum or spin.
  • A participant expresses confusion about the relationship between the spin of photons and the polarization of the electric field, highlighting the difference in eigenstates between spin-1 particles and the two-state problem of E polarization.
  • It is mentioned that massive spin-1 particles have left-handed, right-handed, and longitudinal polarization states, while massless particles like photons only have left-handed and right-handed states corresponding to circular polarization.
  • A question is raised regarding the prohibition of spin-0 states for massless particles, seeking to understand the underlying principle.
  • Another participant speculates that the absence of mass necessitates a mechanism for existence, hinting at a deeper principle.
  • A later reply suggests that the reasoning behind this prohibition may relate to Lorentz invariance, referencing a specific page in a book for further reading.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and agreement on the concepts discussed, with some points remaining contested, particularly regarding the connection between spin and polarization, and the implications of mass on particle states.

Contextual Notes

Participants reference specific properties of particles and their polarization states, but the discussion does not resolve the underlying principles or assumptions regarding massless particles and spin-0 states.

wotanub
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I was reading in my QM book that neutrinos are "essentially left handedly polarized." (Townsend on Page 119)

If neutrinos can be polarized, what is oscillating? Do other particles with mass exhibit polarization?
 
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Yes. You don't need oscillation to get polarization. Particles can have intrinsic angular momentum, called spin.
 
I'm not sure I understand completely.

What's the connection between spin of a photon and the polarization of the E field? Photons are spin 1 (3 eigenstates) and E polarization is a two state problem. I can't think of an obvious correspondence.
 
Massive spin-1 particles have left-handed, right-handed and longitudinal polarization states. Massless ones like photons have only the left-handed and right-handed states, which are the two varieties of circular polarization.
 
Is there a good reason spin-0 states are forbidden for massless particles? What's the underlying principle?
 
maybe because without mass they need something to keep them existing?
 

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