Does charge conjugation affect parity?

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SUMMARY

The discussion centers on the relationship between charge conjugation and parity in particle physics, specifically addressing the apparent contradiction between statements from Wikipedia and A. Zee's "Quantum Field Theory in a Nutshell." It is established that charge conjugation transforms a left-handed neutrino into a left-handed antineutrino, while Zee's assertion indicates that the charge conjugate of a left-handed field is right-handed. The analysis reveals that both statements hold true under specific conditions, particularly when considering the structure of Dirac fields and Weyl fields.

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  • Understanding of charge conjugation in quantum field theory
  • Familiarity with chirality and its implications in the Standard Model
  • Knowledge of Dirac and Weyl fields
  • Basic grasp of the properties of the gamma matrices, particularly ##\gamma_5##
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This discussion is beneficial for theoretical physicists, graduate students in particle physics, and researchers focusing on quantum field theory and the Standard Model of particle physics.

silmaril89
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"Notice that these transformations do not alter the chirality of particles. A left-handed neutrino would be taken by charge conjugation into a left-handed antineutrino, which does not interact in the Standard Model." --https://en.wikipedia.org/wiki/C-symmetry

The excerpt above seems to unambiguously answer this question. But, then:

"You can easily convince yourself (exercise II.1.9) that the charge conjugate of a left handed field is right handed and vice versa." --Quantum Field Theory in a Nutshell, A. Zee

These statements appear to be contradictory. What's going on here?

Also, it does seem easy to convince myself of Zee's comment (following Zee's convention that \psi \to \psi_c = \gamma^2 \psi^\ast):

Suppose \psi is left-handed (i.e. P_L \psi = \psi and P_R \psi = 0), then
P_L \psi_c = P_L \gamma^2 \psi^\ast = \gamma^2 P_R \psi^\ast = \gamma^2 (P_R \psi)^\ast = 0
and
P_R \psi_c = P_R \gamma^2 \psi^\ast = \gamma^2 P_L \psi^\ast = \gamma^2 (P_L \psi)^\ast = \psi_c
Therefore, it appears that Zee's comment is correct. Can anyone help me understand why the two quotes above are or are not in contradiction?
 
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Both statements are technically true, but I think Zee's is misleading. If we work in basis where ##\gamma_5## is diagonal, then a Dirac field ##\Psi## can be written as a left-handed Weyl field ##\chi## stacked on top of a right-handed Weyl field ##\xi^\dagger##,
\Psi=\pmatrix{\chi\cr\xi^\dagger}
The charge conjugate field is then
\Psi^c=\pmatrix{\xi\cr\chi^\dagger}
Now if we set ##\xi=0##, then we recover Zee's statement (and your algebra). But I think it is more correct to say that the charge conjugate of the left-handed field ##\chi## is the left-handed field ##\xi##. Then, if we use ##\Psi## as a Dirac field for neutrinos, ##\chi## creates left-handed neutrinos, and ##\xi## creates left-handed antineutrinos, which is consistent with the wikipedia statement.
 
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Ok, thanks for the reply. I think I'm still a little confused, but you've put me in a particular direction to begin investigating this further.
 

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