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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- Graph plotted in 2002 – slightly outdated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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