How can there be antineutrinos?

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Discussion Overview

The discussion revolves around the existence of antineutrinos and their relationship to neutrinos, exploring the nature of antimatter and the distinctions between the two types of particles. The scope includes theoretical considerations and experimental observations related to particle physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question how antineutrinos can exist given that neutrinos have no charge, suggesting that the distinction may not solely rely on charge differences.
  • Others clarify that the difference between matter and antimatter extends beyond charge, citing the existence of antineutrons made of antiquarks.
  • One participant notes that antineutrinos have a fermion number of -1, implying a specific interaction behavior with neutrinos.
  • There is a suggestion that neutrinos may possess nonvanishing magnetic dipole moments, with differing orientations relative to their spins in neutrinos and antineutrinos.
  • Evidence for antineutrinos is mentioned, with observations indicating they have spins opposite to those of neutrinos.
  • Another participant describes how neutrinos and antineutrinos can be distinguished in accelerator experiments based on the types of leptons produced in interactions.

Areas of Agreement / Disagreement

Participants express varying views on the nature of antineutrinos and how they can be differentiated from neutrinos. There is no consensus on the implications of their properties or the mechanisms behind their detection.

Contextual Notes

The discussion includes assumptions about particle interactions and properties that may not be fully resolved, particularly regarding the nature of neutrinos and antineutrinos in experimental contexts.

KeplerJunior
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I was wondering how it is possible for there to be anti-neutrinos when antimatter is is identical to matter apart from having the opposite charge. However neutrinos have 0 charge so how can they have anti-neutrinos.
 
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The difference between matter and antimatter is not just opposite charge. Antineutrons exist, being made of antiquarks.

The question about antineutrinos is whether or not they are the same as neutrinos.
 
Antineutrinos have fermion number -1. So a neutrino can annihilate with an antineutro, but not with another neutrino.

Also, I could be wrong about this, but I believe neutrinos have nonvanishing magnetic dipole moments, and the directions of these relative to the spin would be opposite in the two cases.
 
It seems there is pretty good evidence for anti neutrinos...it seems thay have been detected. So far observations indicate they have spin opposite that of the left hand neutrino spin.
 
The way you tell neutrinos and antineutrinos apart in accelerator experiments is to smack them into something and see what comes out. If it includes one net negative lepton (e-, mu- or tau-), you had a neutrino. If it includes one net positive lepton (e+, mu+ or tau+), you had an antineutrino. These interactions proceed via a virtual W boson ("weak charged current interaction").

If you get no leptons coming out, or an even number of them, but there's a lot of "missing" energy and momentum, then you probably had a neutrino or antineutrino coming out, and you can't really tell the difference. These interactions proceed via a virtual Z boson ("weak neutral current").
 

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