[itex]\pi^0[/itex]s decay to two photons via the EM interaction. The [itex]J^{PC}[/itex] of the pion is [itex]0^{-+}[/itex] and of a [itex]\gamma[/itex] is [itex]1^{--}[/itex].(adsbygoogle = window.adsbygoogle || []).push({});

[itex]\gamma\gamma[/itex] therefore has [itex]J^{PC} = 0^{++}, 1^{-+}, 2^{++}[/itex].

This does not match the pion, so how can this decay occur?

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# Neutral pion decay: JPC conservation

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