Mixing and production of exotic fermions in E6

The mixings between exotic fermions in E6 27-plets (a Q = -(1/3) isosinglet quark h and charged and neutral leptons E and ν/sub E/) and their familiar counterparts d, e, and ν/sub e/ are discussed and constraints from electroweak neutral-current data on such mixings are examined. We find off-diagonal couplings dh-barZ0, eE-barZ0, and ν/sub e/nu-bar/sub E/Z0 and propose new methods for single production of such new fermions in e+e- collisions and Z decay. Such couplings also lead (in general) to flavor-changing neutral currents and we examine constraints on the masses and mixings of the h quarks which can be derived from the K0-K0 system and K/sub L/→μ+μ-