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Neutral pion decay

by physguy09
Tags: decay, neutral, pion
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May15-09, 10:59 AM
P: 19
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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May15-09, 11:46 AM
P: 23
What makes you think it isn't an electromagnetic decay?

I would say that it is.
May15-09, 12:04 PM
PF Gold
arivero's Avatar
P: 2,921
EM it is, but anomaly.

Hans de Vries
May16-09, 06:08 AM
Sci Advisor
P: 1,135
Neutral pion decay

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

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