Tadpole-induced electroweak symmetry breaking and pNGB Higgs models

Abstract

We investigate induced electroweak symmetry breaking (EWSB) in models in which the Higgs is a pseudo-Nambu-Goldstone boson (pNGB). In pNGB Higgs models, Higgs properties and precision electroweak measurements imply a hierarchy between the EWSB and global symmetry-breaking scales, vH ≪ fH. When the pNGB potential is generated radiatively, this hierarchy requires fine-tuning to a degree of at least ∼ vh2/fH2. We show that if Higgs EWSB is induced by a tadpole arising from an auxiliary sector at scale fΣ ≪ vH, this tuning is significantly ameliorated or can even be removed. We present explicit examples both in Composite Higgs models based on SO(5)/SO(4) and in Twin Higgs models. For the Twin case, the result is a fully natural model with fH ∼ 1 TeV and the lightest colored top partners at 2 TeV. These models also have an appealing mechanism to generate the scales of the auxiliary sector and Higgs EWSB directly from the scale fH, with a natural hierarchy fΣ ≪ vH ≪ fH ∼ TeV. The framework predicts modified Higgs coupling as well as new Higgs and vector states at LHC13.