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one of my books says, that a charmonium [tex]c\bar c[/tex] in the sate [tex]1^1S_0[/tex] could decay into two phtons: [tex]c \bar c \rightarrow 2\gamma[/tex]

But I think, conservation of parity is violated (not allowed, since we have electromagnetic interaction)

Parity of a charmonium state is [tex](-1)^{L+1}[/tex], we have L=0, so before the decay we have a parity of -1.

Parity of a photon is -1, we have two photns, so the parity after the decay is +1

So, where have I made an error in reasoning?

--derivator

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# Charmonium: two photon decay

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