Unification with vector-like fermions and signals at LHC

Abstract

Abstract:We look for minimal extensions of Standard Model with vector like fermions leading to precision unification of gauge couplings. Constraints from proton decay, Higgs stability and perturbativity are considered. The simplest models contain several copies of vector fermions in two different (incomplete) representations. Some of these models encompass Type III seesaw mechanism for neutrino masses whereas some others have a dark matter candidate. In all the models, at least one of the candidates has non-trivial representation under SU(3) color . In the limit of vanishing Yukawa couplings, new QCD bound states are formed, which can be probed at LHC. The present limits based on results from 13 TeV already probe these particles for masses around a TeV. Similar models can be constructed with three or four vector representations, examples of which are presented.

Road map through the desert: unification with vector-like fermions

“…2 In the present work, we build on the findings of Ref. [28] and extend their analysis in several different directions. First of all, we boost the allowed mass range of VL fermions up to 10 TeV.…”

“…3 that several novel solutions with respect to those presented in Ref. [28] can be found if that somewhat arbitrary assumption is relaxed.…”

“…3. It is, however, a known fact [28] that precise unification is not possible within such a framework. The next possibility is then to consider two different VL representations with an arbitrary number of fermion copies within each of them.…”

“…The issue of gauge coupling unification in the presence of VL fermions is not a new idea and it received a lot of attention in the literarture, both before the launch of the LHC [14,15,16,17,18,19,20,21,22,23], and after [24,25,26,27,28,10]. Similar analyses within the SUSY framework were performed as well [29,30,31,32,33,34,35,36].…”

“…It turns out that, when this extra condition is discarded, novel solutions with respect to Ref. [28] can be found. Finally, we thoroughly discuss a variety of experimental methods that allow one to test the successful unification scenarios.…”