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Universal Extra Dimensions. Universal Extra Dimensions. All Standard Model fields propagate into the bulk, typically 1 or 2 extra dimensions. Momentum conservation principle manifests as a conservation of a parity at each vertex – KK parity Naturally provides a Dark Matter candidate

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## Universal Extra Dimensions

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**Universal Extra Dimensions**• All Standard Model fields propagate into the bulk, typically 1 or 2 extra dimensions. • Momentum conservation principle manifests as a conservation of a parity at each vertex – KK parity • Naturally provides a Dark Matter candidate • Excited modes mimic Standard Model zero modes. • Minimal number of extra parameters • R, Λ and mH**Toy derivation of scalar Lagrangian**• Heuristic derivation showing how mass terms appear – infinite tower of KK modes**Dark Matter CandidatesAnalysis by Servant & Tait**• Neutral Weak Gauge Boson B1 • Strongest CDM candidate • Neutrino • disfavored by present limits from direct detection experiments**Why B(1)?**• The mass matrix that governs the mixing between the neutral weak gauge bosons is • The B(1) is mostly photon**What’s involved?**• If UED theories are incorrect, the LHC will be able to exclude them in their present form. • Cosmological constraints place R within the reach of LHC energies. • Confirmation of the theory will require more extensive statistics, because SUSY will have the same signature(s) as UEDs within the statistical reach, at the KK1 level. • Require higher statistics → better angular resolution of decay products → spin determination • Correlation with cosmological experiments • Require resolution of higher KK modes for model resolution**Servant, TaitPrediction for ΩB(1)h2**• hep-ph/0206071 • Graph plotted in 2002 – slightly outdated • Lower band should span 0.09 to 0.13 corresponding to m = 750 - 950 GeV, using latest WMAP results**Requirements for Dark Matter Candidacy**• There must exist a stability mechanism • KK Parity conservation • Electrically neutral • Charged particles could interact with zero mode, and we would have seen them • Coannihilation**Lightest Kaluza-Klein Particle (LKP)**• Stable by virtue of KK parity conservation • All heavier odd-mode particles eventually annihilate/decay into the LKP • KK parity conserved at all levels**radiative corrections to massesat lower limit of R**• Weak gauge boson masses receive almost no correction • Lepton mass correction are a few percent • Gluons & quark masses receive large corrections**radiative corrections to massesat upper limit of R**• Weak gauge boson masses receive almost no correction • Lepton mass correction are a few percent • Gluons & quark masses receive large corrections, but smaller than with smaller R

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