Evasive Higgs Maneuvers at the LHC

TL;DR

This work examines how a Standard Model-like Higgs could evade LHC bounds through non-standard decays by introducing a minimal Higgs-portal interaction with a hidden sector and an effective field theory framework to describe altered widths and decay patterns. The authors classify evasive Higgs phenomenology into Hidden (invisible decays), Reemerging (long-lived decays that reappear as SM states), Buried (dominant hadronic or gluon decays), and Combined hide-outs, providing simple EFT parametrizations and explicit formulas for decay widths and production×branching ratios. They analyze current and proposed search strategies, including monojet+$\slashed E_T$, associated production with a $Z$, and displaced-vertex triggers, to quantify sensitivity to these signatures. The study highlights that light Higgs scenarios can hide with moderate portal couplings, while heavier Higgses demand larger couplings or alternative decay paths, underscoring the need for adapted trigger and reconstruction techniques, such as jet-substructure and outer-detector searches, to improve coverage. Overall, the paper offers a framework and benchmarks to guide future LHC searches toward non-standard Higgs decays that could otherwise go unnoticed.

Abstract

Non-standard decays of the Higgs boson produced at the Large Hadron Collider can lead to signatures which can easily be missed due to non-adapted trigger or search strategies. Keeping electroweak symmetry breaking Standard Model-like we classify the phenomenology of an evasive Higgs boson into three categories and discuss how they can be described in an effective field theory. We comment on how one can improve the search strategies to also detect such an evasive Higgs.

Figures (6)

• Figure 1: Required size of the Higgs portal coupling $\eta$ to achieve an invisible branching ratio of ${\text{BR}}({\text{invis}})=90\%$. We choose $m_\phi=10~{\text{GeV}}$, the result is however rather independent of this choice.
• Figure 2: Expected and observed ($\left\langle\xi\right\rangle=0.27$) 95% CL upper limits on the production cross section in multiples of the SM cross section for a monojet+$\slashed{E}_T$ search confronted with an invisibly decaying Higgs.
• Figure 3: Expected 95% CL upper limits on the associated production cross section in multiples of the SM cross section for a two leptons+$\slashed{E}_T$ search confronted with an invisibly decaying Higgs. Superficially this channel looks more sensitive then the monojet search. Note, however, that this plot does not include any efficiencies and is not based on actual data.
• Figure 4: Probability, based on the Atlas geometry, for a $\phi$ to decay in the tracker, E/H-calorimeter, muon-calorimeter or outside the detector. We show the results for four different average lab frame decay lengths, respectively.
• Figure 5: Probability for the distance between initial Higgs production and final decay back into SM particles for a cascade decay with 1 (blue), 2 (red), 5 (yellow) and 50 (green) intermediate steps.