MSSM extension with a mirror fourth generation, neutrino magnetic moments, and CERN LHC signatures

Abstract

Recent analyses have shown that a sequential fourth generation can be consistent with precision electroweak data. We consider the possibility that the new generation could be a mirror generation with $V+A$ rather than $V\ensuremath{-}A$ interactions. Specifically we consider an extension of the minimal supersymmetric standard model with a light mirror generation. Implications of this extension are explored. One consequence is an enhancement of the $\ensuremath{\tau}$ neutrino magnetic moment by several orders of magnitude consistent with the current limits on the magnetic moment of the $\ensuremath{\tau}$. The masses of the mirror generation arise due to electroweak symmetry breaking, and if a mirror generation exists its mass spectrum must lie below a TeV, and thus should be discovered at the LHC. Mirror particles and mirror sparticles produce many characteristic signatures which should be detectable at the LHC. Heavy Higgs boson decays into mirror particles and an analysis of the forward-backward asymmetries can distinguish a mirror generation from a sequential fourth generation. The validity of the model can thus be tested at the LHC. A model of the type discussed here could arise from a more unified structure such as grand unification or strings where a mirror generation escapes the survival hypothesis, i.e., a generation and a mirror generation do not tie up to acquire a mass of size ${M}_{\mathrm{GUT}}$ or ${M}_{\mathrm{string}}$ due to a symmetry, and thus remain massless down to the electroweak scale.