TopSU(5)models: Baryon and lepton number violating resonances at the LHC

Abstract

We propose minimal and renormalizable nonsupersymmetric top $SU(5)$ models where the $SU(5)\ifmmode\times\else\texttimes\fi{}SU(3{)}_{C}^{\ensuremath{'}}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{L}^{\ensuremath{'}}\ifmmode\times\else\texttimes\fi{}U(1{)}_{Y}^{\ensuremath{'}}$ gauge symmetry is broken down to the Standard Model gauge symmetry at the TeV scale. The first two families of the Standard Model fermions are charged under $SU(3{)}_{C}^{\ensuremath{'}}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{L}^{\ensuremath{'}}\ifmmode\times\else\texttimes\fi{}U(1{)}_{Y}^{\ensuremath{'}}$, while the third family is charged under $SU(5)$. In the minimal top $SU(5)$ model, we show that the quark Cabibbo-Kobayashi-Maskawa mixing matrix can be generated via dimension-five operators, and the proton decay problem can be solved by fine-tuning the coefficients of the higher-dimensional operators at the order of ${10}^{\ensuremath{-}4}$. In the renormalizable top $SU(5)$ model, we can explain the quark Cabibbo-Kobayashi-Maskawa mixing matrix by introducing vectorlike particles, and we do not have the proton decay problem. The models give rise to leptoquark and diquark gauge bosons which violate both lepton and baryon numbers involving the third-family quarks and leptons. The current experimental limits for these particles is well below the TeV scale. We also discuss the productions and decays of these new gauge bosons, and their ensuing signals, as well as their reach at the LHC.