
Using the pinch technique we construct at oneloop order a neutrino charge radius, which is finite, depends neither on the gaugefixing parameter nor on the gaugefixing scheme employed, and is process independent. This definition stems solely from an effective proper photonneutrino oneloop vertex, with no reference to box or selfenergy contributions. The role of the WW box in this construction is critically examined. In particular it is shown that the exclusion of the effective WW box from the definition of the neutrino charge radius is not a matter of convention but is in fact dynamically realized when the target fermions are righthandedly polarized. In this way we obtain a unique decomposition of effective selfenergies, vertices, and boxes, which separately respect electroweak gauge invariance. We elaborate on the treelevel origin of the mechanism which enforces at the oneloop level massive cancellations among the longitudinal momenta appearing in the Feynman diagrams, and in particular those associated with the nonAbelian character of the theory. Various issues related to the known connection between the pinch technique and the background field method are further clarified. Explicit closed expressions for the neutrino charge radius are reported.
