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There was a question about the difference between a neutrino and antineutrino, and answers suggested that weak isospin is different, as well as handedness. This would make sense if you expect pair production of neutrinos is possible, and weak isospin is conserved, you would expect equal and opposite values of weak isospin, but it is confusing when you consider that many theorists use the Majorana equation to describe neutrinos. The equation does not permit a distinction between particles and antiparticles in all reference frames. As far as I know, experimental scientists are still looking for violations of lepton number, so the Majorana neutrino could very well exist.

My question is if real neutrinos are Majorana neutrinos, does that mean their anti-particle does not have a different weak isospin from the particle. If the answer is they do have different weak isospin, are they really different particles.

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  • $\begingroup$ Review the see-saw mechanism to fix your thinking. Neutrinos are very distinguishable from antineutrinos in the lab. If there is (small !) lepton number violation, indeed, the propagating state will have a weak isospin 1/2 component (mostly) and an infinitesimal isosinglet piece. Is this what you are asking? $\endgroup$ Jan 24 '20 at 1:28
  • $\begingroup$ Yes. You answered exactly the question I asked, and I found the answer very useful. $\endgroup$
    – yeaton
    Jan 24 '20 at 2:58
  • $\begingroup$ Useful reference: Kayser 2009. $\endgroup$ Jan 25 '20 at 23:24
  • $\begingroup$ Near duplicate. $\endgroup$ Jan 26 '20 at 15:04

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