Unification without supersymmetry: neutrino mass, proton decay and light leptoquarks

Abstract

We investigate predictions of a minimal realistic non-supersymmetric SU(5) grand unified theory. To accomplish unification and generate neutrino mass we introduce one extra Higgs representation--a 15 of SU(5)--to the particle content of the minimal Georgi-Glashow scenario. Generic prediction of this setup is a set of rather light scalar leptoquarks. In the case of the most natural implementation of the type II see-saw mechanism their mass is in the phenomenologically interesting region (O(10^2--10^3) GeV). As such, our scenario has a potential to be tested at the next generation of collider experiments, particularly at the Large Hadron Collider (LHC) at CERN. The presence of the 15 generates additional contributions to proton decay which, for light scalar leptoquarks, can be more important than the usual gauge d=6 ones. We exhaustively study both and show that the scenario is not excluded by current experimental bounds on nucleon lifetimes.