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Abstract:
Composite Higgs models offer a solution to the hierarchy problem, as the Higgs is no longer an elementary particle, but instead a bound state of some new strong interaction and it arises as a pseudo–Nambu–Goldstone boson of a spontaneous symmetry breaking. Consequently, there is no tree–level potential and the radiative corrections to the Higgs mass are cut off around the compositeness scale. However, in recent years the compositeness scale has been pushed higher and higher, reintroducing a little hierarchy problem, which stems from the non–observation of additional composite resonances with top–like quantum numbers at colliders, an ubiquitous prediction of composite Higgs models. In this work we show how exotic fermions can restore naturalness to composite Higgs models and furthermore predict a lightest composite resonance that differs with respect to generic composite Higgs models. The quadratic contribution of the exotic fermions to the scalar potential cancels the quadratic top contribution and the exotics arise naturally in composite Grand Unified Theories. We give a model–building recipe of how the cancellation mechanism can be included in other models. Two exemplary cosets are analysed in which the lightest partner carries baryon number B = 2/3, leading to a complicated six–particle final state, a signature not yet explored at the LHC.
