Grand unification and light color-octet scalars at the LHC

Abstract

We study the properties and production mechanisms of color-octet scalars at the Large Hadron Collider. We focus on the single production of both charged and neutral members of an (8,2){sub 1/2} doublet through bottom-quark initial states. These channels provide a window to the underlying Yukawa structure of the scalar sector. Color-octet scalars naturally appear in grand unified theories based on the SU(5) gauge symmetry. In the context of adjoint SU(5) these fields are expected to be light to satisfy constraints coming from unification and proton decay, and may have TeV-scale masses. One combination of their couplings is defined by the relation between the down-quark and charged-lepton Yukawa couplings. Observation of these states at the LHC gives an upper bound on the proton lifetime if they truly arise from this grand unified theory. We demonstrate that TeV-mass scalars can be observed over background at the LHC using boosted top-quark final states, and study how well the scalar Yukawa parameters can be measured.