We study the power law running of gauge, Yukawa and quartic scalar couplings in the universal extra dimension scenario where the extra dimension is accessed by all the standard model fields. After compactifying on an S 1 /Z 2 orbifold, we compute one-loop contributions of the relevant Kaluza-Klein (KK) towers to the above couplings up to a cutoff scale Λ. Beyond the scale of inverse radius, once the KK states are excited, these couplings exhibit power law dependence on Λ. As a result of faster running, the gauge couplings tend to unify at a relatively low scale, and we choose our cutoff also around that scale. For example, for a radius R ∼ 1 TeV −1 , the cutoff is around 30 TeV. We then examine the consequences of power law running on the triviality and vacuum stability bounds on the Higgs mass. We also comment that the supersymmetric extension of the scenario requires R −1 to be larger than ∼ 10 10 GeV in order that the gauge couplings remain perturbative up to the scale where they tend to unify.

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Besides supersymmetry, the other prime candidate of physics beyond the standard model (SM), crying out for verification at the CERN Large Hadron Collider (LHC), is extra-dimension. To hunt for effects of Kaluza-Klein (KK) excitations of known fermions and bosons is very much in the agenda of the LHC. These KK states arise when the SM particles penetrate in the extra space-like dimension(s). In this paper, we consider a 5d scenario, called 'Universal Extra Dimension', where the extra space coordinate, compactified on an orbifold S 1 /Z 2 , is accessed by all the particles. The KK number (n) is conserved at all tree level vertices. This entails the production of KK states in pairs and renders the lightest KK particle stable, which leaves the detector carrying away missing energy. The splitting between different KK flavors is controlled by the zero mode masses and the bulk-and brane-induced one-loop radiative corrections. We concentrate on the production of an n = 1 KK electroweak gauge boson in association with an n = 1 KK quark. This leads to a signal consisting of only one jet, one or more leptons and missing p T . For definiteness we usually choose the inverse radius of compactification to be R −1 = 500 GeV, which sets the scale of the lowest lying KK states. We show on a case-by-case basis (depending on the number of leptons in the final state) that with 10 fb −1 integrated luminosity at the LHC with √ s = 14 TeV this signal can be detected over the SM background by imposing appropriate kinematic cuts. We record some of the expectations for a possible intermediate LHC run at √ s = 10 TeV and also exhibit the integrated luminosity required to obtain a 5σ signal as a function of R −1 .