Ok, it is more clear now. It is another thing than gauge theories. It is a coupling for mesons which contributes to their Lagrangians for the interactions with scalars. I think you particle physicists use Dirac Lagrangians for 1/2 spin particles in order to put the mesons interaction into the system. Here the Yukawa interaction represents the interaction between Dirac and Scalar fields.
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Those are not exactly the Yukawa interactions I am talking about, as the context here is the one of the fundamental particles (mesons are composite).