Three sterile neutrinos in E6
  Candidates for unfication of the electroweak and strong interactions include the grand unified groups SU(5), SO(10), and the exceptional group E6. The 27-dimensional fundamental representation of E6 contains exotic fermions, including weak isosinglet quarks of charge -1/3, vector-like weak isodoublet leptons, and neutral leptons which are singlets under both left-handed and right-handed SU(2). These last are candidates for light "sterile" neutrinos, hinted at by some recent short-baseline neutrino experiments. In order to accommodate three families of quarks and charged leptons, an E6 model must contain three 27-plets, each of which contains a sterile neutrino candidate n. The mixing pattern within a 27-plet is described, and experimental consequences are discussed. 
Jonathan L. Rosner
hep-ph astro-ph.HE hep-ex