Spinless photon dark matter from two universal extra dimensions

TL;DR

This paper investigates a novel spin-0 dark matter candidate arising from two universal extra dimensions, analyzing its relic abundance, detection prospects, and distinctive phenomenology compared to single extra dimension models.

Contribution

It introduces the spinless photon as a dark matter candidate in two universal extra dimensions and studies its relic density and detection prospects, highlighting differences from single extra dimension models.

Findings

Relic abundance constrains the spinless photon mass to below 500 GeV.

Direct detection is helicity suppressed, making it challenging but possible.

Indirect detection signals are similar to neutralinos, with low neutrino telescope rates.

Abstract

We explore the properties of dark matter in theories with two universal extra dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle, representing a six-dimensional photon polarized along the extra dimensions. Annihilation of this 'spinless photon' proceeds predominantly through Higgs boson exchange, and is largely independent of other Kaluza-Klein particles. The measured relic abundance sets an upper limit on the spinless photon mass of 500 GeV, which decreases to almost 200 GeV if the Higgs boson is light. The phenomenology of this dark matter candidate is strikingly different from Kaluza-Klein dark matter in theories with one universal extra dimension. Elastic scattering of the spinless photon with quarks is helicity suppressed, making its direct detection challenging, although possible at upcoming experiments. The prospects for indirect detection with gamma rays and antimatter are similar to those of neutralinos. The rates predicted at neutrino telescopes are below the sensitivity of next-generation experiments.