Partially Natural Two Higgs Doublet Models

Abstract

It is possible that the electroweak scale is low due to the fine-tuning of microscopic parameters, which can result from selection effects. The experimental discovery of new light fundamental scalars other than the Standard Model Higgs boson would seem to disfavor this possibility, since generically such states imply parametrically worse fine-tuning with no compelling connection to selection effects. We discuss counterexamples where the Higgs boson is light because of fine-tuning, and a second scalar doublet is light because a discrete symmetry relates its mass to the mass of the Standard Model Higgs boson. Our examples require new vectorlike fermions at the electroweak scale, and the models possess a rich electroweak vacuum structure. The mechanism that we discuss does not protect a small CP-odd Higgs mass in split or high-scale supersymmetry-breaking scenarios of the MSSM due to an incompatibility between the discrete symmetries and holomorphy.

31 pages, 4 figures. v2: refs updated, accepted for publication in JHEP

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Cited by in corpus (8)

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• A natural mechanism for approximate Higgs alignment in the 2HDM
• Bounded masses in Two Higgs Doublets Models, Spontaneous CP Violation and ${\mathbb{Z}}_2$ symmetry
• Higgs Squared
• Exceptional regions of the 2HDM parameter space
• Fine-Tuning in the 2HDM
• QCD and High Energy Interactions: Moriond 2018 Theory Summary