Relic abundance of dark matter in universal extra dimension models with right-handed neutrinos

TL;DR

This paper explores how universal extra dimension models with right-handed neutrinos can account for dark matter relic abundance, avoiding previous issues and aligning with cosmological data.

Contribution

It introduces a viable dark matter candidate in UED models with right-handed neutrinos and analyzes its relic abundance considering various production and decay processes.

Findings

KK right-handed neutrino can be dark matter candidate

Extra dimension scale can be as low as 500 GeV

Models are consistent with cosmological observations

Abstract

Relic abundance of dark matter is investigated in the framework of universal extra dimension models with right-handed neutrinos. These models are free from the serious Kaluza-Klein (KK) graviton problem that the original universal extra dimension model has. The first KK particle of the right-handed neutrino is a candidate for dark matter in this framework, and its relic abundance is determined by three processes, (1) the decay of the KK photon into the first KK right-handed neutrino in the late universe, (2) production of the first KK right-handed neutrino from the thermal bath in the early universe, and (3) the decay of higher KK right-handed neutrinos into the first KK right-handed neutrino in the late universe. When ordinary neutrino masses are large enough such as the degenerate mass spectrum case, the last process contribute to the abundance significantly, even if the reheating temperature is low. The scale of the extra dimension consistent with cosmological observations can be 500 GeV in the minimal setup of universal extra dimension models with right-handed neutrinos.