Higgs singlet extension parameter space in the light of the LHC discovery

In this article we propose an overview on the current theoretical and experimental limits on a Higgs singlet extension of the Standard Model (SM). We assume that the boson which has recently been observed by the LHC experiments is the lightest Higgs boson of such a model, while for the second Higgs boson we consider a mass range of 600 GeV <= m(H) <= 1 TeV, where our model directly corresponds to a benchmark scenario of the heavy Higgs working group. In this light, we study the impact of perturbative unitarity limits, renormalization group equations analysis, and experimental constraints (electroweak precision tests, measurements of the observed light Higgs coupling strength 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 of 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 kappa as well as the total width Gamma of the new scalar.