The Higgs Singlet extension parameter space in the light of the LHC discovery

TL;DR

This paper reviews theoretical and experimental constraints on a Higgs singlet extension of the Standard Model, focusing on a heavy second Higgs boson and its implications for LHC searches.

Contribution

It provides a comprehensive analysis of the parameter space for a Higgs singlet extension considering current limits and explores the impact on LHC search strategies.

Findings

Perturbativity and vacuum stability restrict the allowed Higgs mixing range.

Heavy Higgs masses above 600 GeV are constrained by theoretical limits.

Expected suppression factors for SM-like decays of the heavy Higgs are discussed.

Abstract

In this note we propose an overview on the current theoretical and experimental limits on a Higgs singlet extension of the Standard Model. We assume that the Boson which has recently been measured by the LHC experiments is the lightest Higgs boson of such model, while for the second Higgs Boson we consider a mass range of 600 GeV to 1 TeV, i.e. outside the range of the direct searches presented so far. In this light, we study the impact of perturbative unitarity limits, Renormalisation Group Equations analysis and experimental constraints (Electro-Weak Precision Tests, measurements of the light Higgs coupling at the Large Hadron Collider). We show that, in the case of no additional hidden sector contributions, the largest constraints for higher Higgs masses stem from the assumption of perturbativity as well as vacuum stability for scales on the order of the SM metastability scale, and that the allowed mixing range is severely restricted. We discuss implications for current LHC searches in the singlet extension, especially the expected suppression factors for SM-like decays of the heavy Higgs. We present these results in terms of a global scaling factor as well as the total width of the new scalar.