How does handedness get preserved in this situation?

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Discussion Overview

The discussion revolves around the preservation of handedness in neutrinos, particularly in relation to their spin, helicity, and chirality. Participants explore the implications of different frames of reference on these properties, as well as the clarity of explanations provided in a video by a nuclear physicist.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that neutrinos travel in relation to their spin and questions whether spin changes based on the frame of reference, given that neutrinos can be outrun by higher energy neutrinos.
  • Another participant clarifies the distinction between spin, helicity, and chirality, noting that for massive particles, only spin is conserved, while helicity and chirality can vary.
  • A third participant expresses confusion regarding the video's focus on quantum spin, questioning the accuracy of the physicist's explanation.
  • A later reply argues that expecting a complete description in a short video is unrealistic.

Areas of Agreement / Disagreement

Participants express differing views on the clarity and accuracy of the video's content, with some agreeing that the explanation may be insufficient while others defend the physicist's credibility. The discussion remains unresolved regarding the implications of frame of reference on neutrino properties.

Contextual Notes

Participants highlight potential misunderstandings related to the definitions of spin, helicity, and chirality, as well as the limitations of a brief video format in conveying complex concepts.

newjerseyrunner
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In this video it's explained that neutrinos always travel related to the direction of their spin. But neutrinos don't travel at the speed of light, so it's possible to outrun it.

That means from the point of view of earth, a solar neutrino is moving in one direction. But to a higher energy neutrino chasing it, it's moving in the opposite direction.

So does spin change based on frame of reference?
 
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You are mixing several concepts, spin, helicity and chirality. For a massive particle, only spin is conserved while helicity and chirality aren't. Also helicity and chirality don't coincide. For a massless particle, spin is not well defined (as it is angular momentum in the rest frame, which does not exist for a massless particle), while helicity and chirality coincide.
So yes, you can outrun a neutrino and change its helicity.
 
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I'm confused, the video seemed to only mention quantum spin. Was this a mistake? The guys a nuclear phycisist at fermilabs, seems unlikely that he'd make a mistake like that.
 
Expecting a complete description in a nine minute video is unrealistic.
 

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