On the space-time structure of the neutral weak current. A generalized version of the confusion theorem

There is a strong belief among physicists that neutral weak currents are a mixture of vector and axial vector currents. Nevertheless there is no experiment which can exclude scalar, pseudoscalar and tensor coupling. In this paper we discuss the most general form of neutrino scattering on a hadronic target via a neutral current. Comparison between SPT and VA cross sections leads to an even stronger version of the so-called confusion theorem, which states that any y distribution possible for a VA cross section can be simulated by SPT coupling. Even positivity constraints on the hadron tensor are not strong enough to exclude SPT coupling, if the measurements are compatible with a VA theory.