Show that C=-1 for a photon and hence that C= +1 for a π^0....

Name: Problem 25, Chapter 12: Quarks and leptons: introductory course in modern particle physics
Uploaded: 2021-06-17T00:16:42-08:00
Duration: 2 min 48 s
Channel: Nicole Smina
Description: Show that C=-1 for a photon and hence that C= +1 for a π^0.

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Key Concepts

Charge Conjugation (C-Parity)

Charge conjugation is a discrete symmetry operation in quantum field theory that transforms a particle into its corresponding antiparticle. The C-parity eigenvalue of a state provides information about how that state behaves under the exchange of particles with antiparticles and plays an important role in understanding the electromagnetic and strong interactions.

Photon C-Parity

The photon, being a gauge boson mediating the electromagnetic interaction, transforms under charge conjugation by changing the sign of its vector potential. This transformation results in the photon acquiring an intrinsic C-parity eigenvalue of -1. This property is crucial in analyzing processes involving photons and assessing symmetry conservation in electromagnetic interactions.

Neutral Pion C-Parity from Two-Photon Decay

The neutral pion (?0) is observed to decay predominantly into two photons. Since each photon carries a C-parity of -1, the overall C-parity for the two-photon system is obtained by multiplying the individual eigenvalues (and including any necessary orbital angular momentum factors, which in the simplest case do not alter the sign). Thus, (-1)×(-1) yields an overall C-parity of +1 for the ?0. This result is a direct consequence of the properties of charge conjugation symmetry applied to composite systems.

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