New spectra in the HEIDI Higgs models

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 \nu\approx 56\pm12 \gev, largely independent of the dimension. In the limiting case of $d\rightarrow 6$ and two peaks we find a higher dimensional coupling constant $\alpha_6=0.70 \pm 0.18$, indicative of strong interactions among the higher dimensional fields. The LHC will not be able to study this Higgs field.Comment: 17 pages, 4 figure

Radiative corrections in a minimal extension of the standard model

Radiative corrections are studied within an extension of the standard model, containing extra singlet scalars. The calculations determine the effect of a large width of the Higgs boson on radiative corrections. They throw some light on the treatment of unstable particles inside loop-graphs.Comment: 5 pages, LaTeX, 1 eps-figur

Three-Loop Electroweak Correction to the Rho Parameter in the Large Higgs Mass Limit

We present an analytical calculation of the leading three-loop radiative correction to the rho-parameter in the Standard Model in the large Higgs mass limit. This correction, of order g^6 m_H^4/M_W^4, is opposite in sign to the leading two-loop correction of order g^4 m_H^2/M_W^2. The two corrections cancel each other for a Higgs mass of approximately 480 GeV. The result shows that it is extremely unlikely that a strongly interacting Higgs sector could fit the data of electroweak precision measurements.Comment: 15 pages, late

A higher dimensional explanation of the excess of Higgs-like events at CERN LEP

Searches for the SM Higgs boson by the four LEP experiments have found a 2.3 sigma excess at 98 GeV and a smaller 1.7 sigma at around 115 GeV. We interpret these excesses as evidence for a Higgs boson coupled to a higher dimensional singlet scalar. The fit implies a relatively low dimensional mixing scale mu_{lhd} < 50 GeV, which explains the low confidence level found for the background fit in the range s^{1/2} > 100 GeV. The data show a slight preference for a five-dimensional over a six-dimensional field. This Higgs boson cannot be seen at the LHC, but can be studied at the ILC.Comment: 9 page