Singlet-like Higgs bosons at present and future colliders

TL;DR

This paper thoroughly investigates the phenomenology of singlet-like Higgs bosons, analyzing current constraints and future discovery prospects at colliders, highlighting the complementarity of direct and indirect searches and potential deviations in Higgs couplings.

Contribution

It provides a comprehensive phenomenological analysis of singlet-like Higgs bosons, including constraints, search strategies, and implications for various beyond Standard Model theories.

Findings

Strong complementarity between direct and indirect searches.

Potential for sizeable deviations in the Higgs trilinear coupling.

Future colliders can significantly extend current discovery reach.

Abstract

The presence of extra scalar singlets is a feature of several motivated extensions of the Standard Model, and the mixing of such a singlet with the Higgs boson is allowed to be quite large by current experiments. In this paper we perform a thorough phenomenological study of this possibility. We consider both direct and indirect searches, and we quantify the current constraints as well as the prospects for future hadron and lepton machines - from the forthcoming LHC run up to a futuristic 100 TeV proton-proton collider. The direct reaches are obtained extrapolating the current limits with a technique that we discuss and check with various tests. We find a strong complementarity between direct and indirect searches, with the former dominating for lower values of the singlet mass. We also find that the trilinear Higgs coupling can have sizeable deviations from its Standard Model value, a fact for which we provide an analytical understanding. The results are first presented in a general scalar singlet extension of the Standard Model, taking advantage of the very small number of parameters relevant for the phenomenology. Finally, we specify the same analysis to a few most natural models, i.e. the Next-to-Minimal Supersymmetric Standard Model, Twin Higgs and Composite Higgs.