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

In summary, neutrinos are emitted during the beta-decay process and have spin. Most texts say they have zero or negligible rest mass, but the fact that they travel at the speed of light suggests otherwise. Neutrinos have spin 1/2 and can be distinguished from anti-neutrinos by their leptonic number. They may also constitute dark matter in the universe. Neutrinos exhibit handedness and their fixed helicity allows them to travel at the speed of light. Some physicists believe they have mass due to the observation of neutrino oscillations. However, the exact nature of neutrino mass is still a topic of research and discussion.
  • #1
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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  • #2
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.
 
  • #3
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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  • #4
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?
 
  • #5
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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1. What are neutrinos and why are they important?

Neutrinos are subatomic particles that have no electric charge and very little mass. They are important because they are the most abundant particles in the universe and play a crucial role in many physical processes, such as nuclear reactions and the formation of stars.

2. How do scientists study the properties of neutrinos?

Scientists study neutrinos using a variety of methods, including detecting the particles produced in nuclear reactions, observing the effects of their interactions with matter, and measuring their energy and momentum.

3. What is the spin of a neutrino and why is it important?

The spin of a neutrino is a fundamental property that describes its intrinsic angular momentum. It is important because it affects how neutrinos interact with other particles and can provide clues about their behavior and physical properties.

4. How does the mass of a neutrino impact our understanding of the universe?

The mass of a neutrino is a crucial piece of information for understanding the structure and evolution of the universe. It helps to explain the distribution of matter and the formation of large-scale structures such as galaxies and galaxy clusters.

5. What is the connection between neutrinos and dark matter?

Neutrinos are a possible candidate for dark matter, which is the mysterious substance that makes up about 85% of the total matter in the universe. However, recent research suggests that neutrinos only make up a small fraction of dark matter, and other particles may play a larger role in its composition.

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