Neutral-current constraints on gauge models of weak and electromagnetic interactions

Abstract

Sehgal and Hung and Sakurai have recently argued that neutrino-hadron neutral-current couplings must lie in one of two allowed regions in coupling-parameter space. We study this conjecture using realistic BNL ν μ and ν̄ μ spectra in the elastic ν μp (ν̄ μp) calculations and also study constraints imposed by the q 2-distributions. On comparing to gauge models, we find that the Weinberg-Salam and SU(2) L×SU(2) R×U(1) models fall within one allowed region, while a vectorlike SU(3)×U(1) model and a hybrid SU(2)×U(1) model with a (u, b) R doublet fall in the other region.