Probing dark sector fermions in Higgs precision studies and direct searches

TL;DR

This paper explores how future electron-positron colliders and current hadron colliders can detect fermionic dark sector models through Higgs precision measurements and direct searches, highlighting complementary discovery channels.

Contribution

It introduces a comprehensive analysis of simplified fermionic dark sector models, combining Higgs precision observables with collider search constraints to assess discovery prospects.

Findings

Deviations of 0.5% or more in Higgs production cross-section are detectable at future colliders.

Higgs precision measurements can complement direct LHC searches in certain parameter regions.

Combined constraints from oblique parameters, Higgs decay, and collider searches enhance discovery potential.

Abstract

In this paper, we investigate the discovery prospect of simplified fermionic dark sectors models through Higgs precision measurements at $e^+e^-$ colliders and direct searches at hadron colliders. These models extend the Standard Model with two Majorana or Dirac fermions that are singlets, doublets or triplets under the weak SU(2) group. For all models, we consider two scenarios where the lightest new fermion is either stable, or where it decays into other visible final states. For the Higgs precision observables we primarily focus on $\sigma(e^+e^-\to ZH)$, which can deviate from the Standard Model through one-loop corrections involving the new fermions. Deviations of 0.5\% or more, which could be observable at future $e^+e^-$ colliders, are found for TeV-scale dark sector masses. By combining the constraints from the oblique parameters, $\text{Br}(H\to\gamma\gamma)$, and direct production of the new fermions at the LHC, a comprehensive understanding of the discovery potential of these models can be achieved. In both scenarios, there exist some parameter regions where the Higgs precision measurements can provide complementary information to direct LHC searches.