Universal extra dimensions after Higgs discovery
We show bounds on five- and six-dimensional universal extra dimension (UED) models from the latest results of the Higgs searches at the LHC and from the electroweak precision data for the $S$ and $T$ parameters. We consider the minimal UED model in five dimensions and the ones in six dimensions, compactified on ${T}^{2}/{Z}_{2}$, ${T}^{2}/({Z}_{2}\ifmmode\times\else\texttimes\fi{}{Z}_{2}^{\ensuremath{'}})$, ${T}^{2}/{Z}_{4}$, ${S}^{2}$, ${S}^{2}/{Z}_{2}$, the real projective plane, and the projective sphere. The highest possible ultraviolet cutoff scale for each UED model is evaluated from the electroweak vacuum stability by solving the renormalization group equation of the Higgs self-coupling. This scale turns out to be lower than the conventional one obtained from the perturbativity of the gauge coupling. The resultant 95% C.L. lower bounds on the first Kaluza\char21{}Klein scale from the LHC results and from the $S$, $T$ analysis are 600 and 700 GeV in the minimal UED model, while those in the six-dimensional UED models are 800\char21{}1300 GeV and 900\char21{}1500 GeV, respectively.