Neutral Pion Decay: What Forbids EM Force?

In summary, the neutral pion decays into two gamma particles, which could potentially be an electromagnetic decay. However, it is not forbidden and is under conservation of the axial current density and the Chern Simons current of the electromagnetic field.
  • #1
physguy09
19
0
So I know the neutral pion decays as
[tex] \pi \rightarrow \gamma\gamma [/tex]

my question is though, what forbids this from being an electromagnetic decay? I know it is not decaying via the strong force as there are no quarks resulting from decay. However, I do not see what forbids this from decaying via the EM force, if it is spitting out two gammas, which is the EM force carrier. Parity, G-parity, and Energy are conserved, as well as strangeness and angular momentum, so, what exactly forbids this from being EM?
 
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  • #2
What makes you think it isn't an electromagnetic decay?

I would say that it is.
 
  • #3
EM it is, but anomaly.
 
  • #4
It's not forbidden but it would be under conservation of
the axial current density [itex]j_A^\mu[/itex]. (The latter is only conserved
together with the Chern Simons current of the EM field)

Regards, Hans
 
Last edited:

1. What is a neutral pion?

A neutral pion is a subatomic particle made up of two quarks (one up quark and one anti-down quark) that are bound together by the strong nuclear force. It is the lightest meson and has a mass of approximately 135 times that of an electron.

2. How does a neutral pion decay?

A neutral pion decays into two photons through the strong nuclear force. This process is known as electromagnetic decay or gamma decay. The lifetime of a neutral pion is very short, typically around 8.4 x 10^-17 seconds.

3. Why does the EM force forbid neutral pion decay?

The strong nuclear force is responsible for binding the quarks within a neutral pion together. This force is much stronger than the electromagnetic force, which is responsible for interactions between charged particles. Therefore, the EM force is not strong enough to break apart the neutral pion and cause it to decay.

4. Are there any exceptions to this rule?

Yes, there are a few rare cases where a neutral pion can decay through the electromagnetic force. One example is when a neutral pion interacts with an atomic nucleus, the electromagnetic force can be strong enough to cause it to decay into a photon and a neutral eta meson.

5. What are the implications of neutral pion decay being forbidden by the EM force?

The fact that neutral pion decay is forbidden by the EM force has important implications for our understanding of the fundamental forces in the universe. It also plays a role in the stability of matter and the balance of matter and antimatter in the early universe.

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