Heavy top in an E 6 model for fermionic masses and mixing

Abstract

We present a model for the fermionic masses in the E 6 GUT using loop diagrams involving superheavy and gauge bosons. Those corrections and off-diagonal entries to the diagonal (proportional to each other) tree-level mass matrices. In addition to the corrections induced via ν R considered in the previous version, new genuine E 6 contributions are required. Those involve the neutral, SO(10) invariant, lepton N and allow for solutions with large top mass (up to 250 GeV). Studying then in detail the allowed breaking chains of E 6 the possible solutions are restricted and large values of m t are favoured. We obtain for those chains m t,phys ⪆ 100 GeV and in one special case 105 GeV ⪅ m t,phys ⪅ 125 GeV. The masses and mixing-angles of the light neutrinos are fixed, in the model, by the parameters of the quark sector. Large neutrino mixing is correlated with large m t. An explanation of the solar neutrino puzzle à là MSW requires an intermediate scale around 10 12 GeV - the right one for unification in terms of the recent LEP results. At the same time, the corresponding v μ − v τ mixing and masses account for the depletion of the atmospheric v μ flux observed recently by Kamiokande II andIMB.