Dark matter in UED : the role of the second KK level

TL;DR

This paper calculates the relic abundance of KK-photon dark matter in UED models, highlighting the importance of second KK level resonances and coannihilations, which influence the viable dark matter mass range.

Contribution

It provides a comprehensive calculation including all coannihilation channels and resonances, showing the impact of second KK level particles on dark matter relic abundance in UED.

Findings

Preferred dark matter scale increased to 1.3 TeV

Second KK level resonances significantly affect coannihilation

Nucleon scattering cross section generally small unless KK-quarks are degenerate with LKP

Abstract

We perform a complete calculation of the relic abundance of the KK-photon LKP in the universal extra dimension model including all coannihilation channels and all resonances. We show that the production of level 2 particles which decay dominantly into SM particles contribute significantly to coannihilation processes involving level 1 KK-leptons. As a result the preferred dark matter scale is increased to $R^{-1}=1.3$~TeV. A dark matter candidate at or below the TeV scale can only be found in the non-minimal model by reducing the mass splittings between the KK-particles and the LKP. The LKP nucleon scattering cross section is typically small, $\sigma < 10^{-10}$~pb, unless the KK-quarks are nearly degenerate with the LKP.