= Pseudoscalar Yukawa interaction
{title2=$ig\bar\psi\gamma^5\psi\phi$}
A <pseudoscalar> <Yukawa interaction> couples a <Dirac field> bilinear containing the <chirality> matrix to a spin-zero field. In the standard mostly-minus <gamma matrix> convention with $\gamma^5=i\gamma^0\gamma^1\gamma^2\gamma^3$ and the usual <Dirac adjoint>, $ig\bar\psi\gamma^5\psi\phi$ is Hermitian for real $g$ and real $\phi$. If $\phi$ is a pseudoscalar, the interaction also preserves <parity symmetry in quantum field theory>; if $\phi$ is parity even, it breaks that <symmetry>. Moving the factor $i$ into the definition of $\gamma^5$ changes the displayed vertex coefficient but not the interaction. Each vertex has one bosonic leg and two oppositely oriented fermion legs, and preserves <Dirac fermion number conservation>.
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