$L=i\bar{\Psi }{\gamma }^{\mu }{\partial }_{\mu }\Psi -\bar{\Psi }\Psi -q\bar{\Psi }{\gamma }^0\Psi \Phi +\frac{1}{2}\left({\partial }_{\mu }\Phi \right)\left({\partial }^{\mu }\Phi \right)$