Phenomenology of a Fake Inert Doublet Model

TL;DR

This paper explores a novel approach to physics beyond the Standard Model by introducing fakeons, which are off-shell degrees of freedom, and demonstrates their phenomenological implications in the Inert Doublet Model, affecting Higgs processes without conflicting with existing constraints.

Contribution

It introduces the concept of fakeons into the Inert Doublet Model, showing they evade certain experimental constraints and modify loop-level Higgs properties, offering a new paradigm in particle physics modeling.

Findings

Fake doublet avoids Z-pole constraints.

Fakeons modify Higgs decay and coupling at loop level.

Model maintains Standard Model vacuum stability.

Abstract

We introduce a new way of modeling the physics beyond the Standard Model by considering fake, strictly off-shell degrees of freedom: the fakeons. To demonstrate the approach and exemplify its reach, we re-analyze the phenomenology of the Inert Doublet Model under the assumption that the second doublet is a fakeon. Remarkably, the fake doublet avoids the most stringent $Z$-pole constraints regardless of the chosen mass scale, thereby allowing for the presence of new effects well below the electroweak scale. Furthermore, the absence of on-shell propagation prevents fakeons from inducing missing energy signatures in collider experiments. The distinguishing features of the model appear at the loop level, where fakeons modify the Higgs boson $h\to\gamma\gamma$ decay width and the Higgs trilinear coupling. The running of Standard Model parameters proceeds as in the usual Inert Doublet Model case. Therefore, the fake doublet can also ensure the stability of the Standard Model vacuum. Our work shows that fakeons are a valid alternative to the usual tools of particle physics model building, with the potential to shape a new paradigm, where the significance of the existing experimental constraints towards new physics must necessarily be reconsidered.