Unraveling the Mysteries of Neutrinos: Spin, Mass, and Their Role in Dark Matter

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Discussion Overview

The discussion centers on the properties of neutrinos, specifically their spin, mass, and potential role in dark matter. Participants explore theoretical implications, distinctions between neutrinos and anti-neutrinos, and the relationship between mass and speed in the context of particle physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that neutrinos are emitted during beta decay and have spin 1/2, while questioning their mass and speed.
  • There is a suggestion that if neutrinos have mass, they should travel slower than the speed of light, which raises questions about their behavior.
  • One participant notes that the oscillation of neutrinos between different flavors implies they cannot all be massless, suggesting they must have some mass.
  • Participants discuss the distinction between neutrinos and anti-neutrinos, mentioning that they have opposite leptonic numbers and different helicities.
  • There is curiosity about whether neutrinos could constitute dark matter, with one participant offering a non-committal response of "maybe."
  • Another participant references a lecture on neutrino physics, indicating interest in further exploration of the topic.

Areas of Agreement / Disagreement

Participants express differing views on the mass of neutrinos and their implications for speed and behavior. The discussion remains unresolved regarding the nature of neutrinos and their role in dark matter.

Contextual Notes

Some claims about neutrinos having zero rest mass are challenged by the implications of flavor oscillation, but the discussion does not reach a consensus on these points. The relationship between mass, speed, and helicity is also explored without definitive conclusions.

Reshma
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Neutrinos are emitted during the beta-decay process.
Neutrinos definitely have spin. Do neutrinos have mass? Most texts say neutrinos have zero or negligible rest mass. But Neutrinos travel with the speed of light. So how can any particle with finite mass travel with the speed of light? If so how would it make neutrinos different from an electromagnetic wave?

A neutrino has spin 1/2. An anti-neutrino also has spin 1/2. How is it possible to distinguish a neutrino from an anti-neutrino?

Lastly, just out of curiosity :wink: , do neutrinos constitute the dark matter in the universe?
 
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For the last question: maybe.

Chirality is the answer to the penultimate.

If they have mass, then their speed should be less than c, obviously.

Daniel.
 
Reshma said:
Do neutrinos have mass?
It seems they do ! The number of neutrinos we receive from the sun indicates neutrinos oscillate between different flavors. This indicates they cannot all have the same mass (so they cannot all be massless).
If so how would it make neutrinos different from an electromagnetic wave?
Photons have spin one ! Neutrinos are fermions.
How is it possible to distinguish a neutrino from an anti-neutrino?
They have opposite leptonic number. For instance in beta decay, an anti-neutrino is emited with the electron, so that lepton number is conserved.
 
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Thank you Humanino and dextercioby for replying!
humanino said:
It seems they do ! The number of neutrinos we receive from the sun indicates neutrinos oscillate between different flavors. This indicates they cannot all have the same mass (so they cannot all be massless).
Really? What does this mean qualitatively? Why do they have zero rest mass?
dextercioby said:
If they have mass, then their speed should be less than c, obviously.
My book says neutrinos exhibit handedness similar to a screw. A neutrino has spin always anti-parallel to its momentum while an anti-neutrino has spin parallel to its momentum. So, neutrino is a left handed particle and an anti-neutrino is right-handed particle :cool: .
This fixed helicity allows the neutrino and anti-neutrino to move with the velocity of light c. What does this mean?
 
I found a great lecture online from Michael Shaevitz from Columbia University on Neutrino Physics:

http://www.nevis.columbia.edu/~shaevitz/talks/NeutrinoLectureWriteup.pdf

I thought it was well written.
Cheers,
Ryan
 
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