Renormalization of the QED of second order spin 1/2 fermions

Abstract: In this work we study the renormalization of the electrodynamics of spin 1/2 fermions in the Poincar\'e projector formalism which is second order in the derivatives of the fields. We analyze the superficial degree of divergence of the vertex functions of this theory, calculate at one-loop level the vacuum polarization, fermion self-energy and \gamma-fermion-fermion vertex function and the divergent piece of the one-loop contributions to the \gamma-\gamma-fermion-fermion vertex function. It is shown that these functions are renormalizable independently of the value of the gyromagnetic factor g which is a free parameter of the theory. We find a photon propagator and a running coupling constant \alpha (q^2) that depend on the value of g. The magnetic moment form factor contains a divergence associated to g which disappears for g=2 but in general requires the coupling g to be renormalized. A suitable choice of the renormalization condition for the magnetic form factor yields the one loop finite correction \Delta{g}=g\alpha/2\pi. For a particle with g=2 we recover results of Dirac theory for the photon propagator, the running of \alpha (q^2) and the one-loop corrections to the gyromagnetic factor.