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According to wikipedia, the OZI rule states that any strongly occurring process will be suppressed if, through only the removal of internal gluon lines, its Feynman diagram can be separated into two disconnected diagrams: one containing all of the initial-state particles and one containing all of the final-state particles.

However, in the solution manual to Griffiths "Introduction to Elementary Particles", problem 2.10, it is stated the the proccess $\psi'\rightarrow\psi+\pi^{+}+\pi^{-}$ is OZI suppressed, even though the Feynman diagram looks as follows:

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Clearly, according to wikipedia's definition this diagram does not satisfy the OZI rule, so what would be an alternative definition that would fit to the aformentioned decay?

Trish
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1 Answers1

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Indeed, the WP article is slightly glib: perhaps you wish to read it, instead, as " ...can be separated into disconnected diagrams, some containing just final-state particles".

You are meant to understand the "why" provided by asymptotic freedom, not quibble about theological demarcations. The OZI rule is about suppression of purely gluon diagrammatic channels. The sentence of that article you should have focussed on is

An explanation of the OZI rule can be seen from the decrease of the coupling constant in QCD with increasing energy (or momentum transfer). For the OZI suppressed channels, the gluons must have high $q^2$ (at least as much as the rest mass energies of the quarks into which they decay) and so the coupling constant will appear small to these gluons.

Cosmas Zachos
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