Genevieve Belanger, Alexander Belyaev, Matthew Brown, Mitsuru Kakizaki, Alexander Pukhov
Large Hadron Collider (LHC) searches for the SM Higgs boson provide a powerful limit on models involving Universal Extra Dimensions (UED) where the Higgs production is enhanced. We have evaluated all one-loop diagrams for Higgs production $gg\to h$ and decay $h\to \gamma\gamma$ within "minimal" UED (mUED), independently confirming previous results, and we have evaluated enhancement factors for Higgs boson production and decay over the mUED parameter space. Using these we have derived limits on the parameter space, combining data from both ATLAS and CMS collaborations for the most recent 7 TeV LHC data. We have performed a rigorous statistical combination of several Higgs boson search channels which is important because mUED signatures from the Higgs boson are not universally enhanced. We have found that $R^{-1}<500$ GeV is excluded at 95% CL, while for larger $R^{-1}$ only a very narrow ($\pm 1-3$ GeV) mass window around $m_h=125$ GeV is left. This is the region where the excess of the events in the Higgs search channels is reported by the ATLAS and CMS collaborations and where the exclusion limit is weaker. It is worth stressing that mUED predicts an enhancement for all channels for $gg\to h$ production and decay while the vector boson fusion process $WW/ZZ \to h \to \gamma\gamma$ is generically suppressed and $WW/ZZ \to h \to WW^*/ZZ^*$ is standard. Therefore, in the event that a Higgs boson discovery is announced after analysis of the 8 TeV LHC data, the information on individual Higgs boson production and decay processes provided by the CMS and ATLAS experiments can be effectively used to favour or exclude further mUED.
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http://arxiv.org/abs/1207.0798
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