Neutral Pion Decay: Why Can't it Produce Three Photons?

In summary, the PDG states that the neutral pion cannot decay to three photons due to a violation of charge conjugation. This is because the pion is its own antiparticle and has a different eigenvalue for charge conjugation than the photon. Additionally, the pion's ability to decay into two photons is determined experimentally and theoretically by its eigenvalue of C=+1. Therefore, it is not allowed for the neutral pion to decay to three photons.
  • #1
akr
2
0
Why is it not allowed for the neutral pion to decay to three photons? The PDG states that this mode violates charge conjugation, although obviously the two photon decay is the dominant decay of this particle, and I don't see how adding another neutral particle to the decay causes a violation of charge.

Thanks in advance!
 
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  • #2
Note that it is also forbidden to decay to two photons.
 
  • #3
"Charge conjugation" invariance is different than charge conservation.
There is a quantum operator C which converts a particle into its antiparticle.
Particles like the photon and pizero are their own antiparticles.
They are eigenstates of the charge conjugation operator C.
The photon has eigenvalue C=-1, which is determined by how it enters QED.
The pizero has eigenvalue C=+1, which is determined experimentally by the fact that it decays into two photons and not three (The operator C is a multiplicative operator.), and theoretically by the quark model. A particle with C=+1 cannot decay into an odd number of photons.
 
  • #4
Thanks very much!
 

1. What is a neutral pion?

A neutral pion is a subatomic particle that is composed of a quark and an antiquark. It has a mass of approximately 135 MeV/c2 and a spin of zero, making it a boson.

2. What is the decay process of neutral pions?

Neutral pions decay through the strong interaction into two photons. This process occurs due to the instability of the pion, which has a short lifetime of about 8.4 x 10-17 seconds.

3. What are the implications of neutral pion decay?

The decay of neutral pions has important implications in particle physics, as it is a rare example of a decay process that violates charge conjugation and parity symmetry. It also allows for the study of the strong interaction and the properties of the pion.

4. How is neutral pion decay studied?

Neutral pion decay is studied through experiments in high-energy particle accelerators, such as the Large Hadron Collider. Scientists also use theoretical models and simulations to understand the process and its implications.

5. What are the potential applications of understanding neutral pion decay?

Understanding neutral pion decay can lead to a better understanding of the fundamental forces and particles in the universe. It also has potential applications in fields such as nuclear physics, astrophysics, and medical imaging.

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