Electric charge and magnetic moment of massive neutrino

Abstract

We consider a massive Dirac neutrino electric charge and magnetic moment within the context of the standard model supplied with SU(2)-singlet right-handed neutrino in arbitrary R_ξgauge. Using the dimensional-regularization scheme we start with calculations of the one-loop contributions to the neutrino electromagnetic vertex function exactly accounting for the neutrino and other particles masses. We examine the decomposition of the massive neutrino electromagnetic vertex function and show that it contains only the four form factors. Then we get the closed integral expressions for different contributions to the neutrino electric charge and magnetic form factors. These calculations enable us to follow the neutrino and corresponding charged lepton masses and gauge-fixing parameters dependence. For several one-loop contributions to the neutrino charge and magnetic moment, that were calculated previously by the other authors with mistakes, we find the correct results. We show that the neutrino charge for massive neutrino is a gauge independent and vanishing value in the first two orders of the expansion over the neutrino mass parameter b. In the particular choice of the 't Hooft-Feynman gauge we also demonstrate that the neutrino charge is zero for arbitrary mass of neutrino. For each of the diagrams contributing to the neutrino magnetic moment, we get expressions accounting for the leading and next-to-leading order in b with the gauge dependence shown explicitly. Each of the contributions are finite and the sum of all contributions turns out to be gauge-independent. Our calculations also enable us to get the magnetic moment of a heavy neutrino.