Charged vector mesons andξformalism

We discuss a finite-$\xi$ formalism for the electromagnetic interaction of a massive charged vector meson with an arbitrary magnetic moment $\kappa$. The theory is Lorentz-covariant, renormalizable, and gauge-invariant. We consider the case $\xi =\kappa =1\mathrm{}$ to show that the theory is unitary after introducing a fictitious particle and two new vertices in the theory.