New spectra in the HEIDI Higgs models Original Research Article

We study the so-called HEIDI models, which are renormalizable extensions of the standard model with a higher-dimensional scalar singlet field. As an additional parameter we consider a higher-dimensional mixing mass parameter. This leads to enriched possibilities compared to a previous study. We find effective spectral densities of the Higgs propagator, consisting of one, two or no particle peaks, together with a continuum. We compare with the LEP-2 data and determine for which range of the model parameters the data can be described. Assuming two peaks to be present we find for the new mass scale image, largely independent of the dimension. In the limiting case of image and two peaks we find a higher-dimensional coupling constant image, indicative of strong interactions among the higher-dimensional fields. This Higgs might escape discovery at the LHC. That would provide a strong physics case for building a new lepton collider.