Fermi Gamma-ray Space Telescope

Gamma-ray spectrum from annihilation of Kaluza-Klein dark matter and its observability

Satoshi Tsuchida
Masaki Mori

Abstract:

The theory of universal extra dimensions includes Kaluza-Klein (KK) particles. The lightest KK particle (LKP) is one of the good candidates of cold dark matter. Annihilation of LKP dark matter in the Galactic halo produces high-energy gamma-rays. The gamma-ray spectrum shows a characteristic peak structure around the LKP mass. Here, we investigate the detectability of this peak structure by near-future detectors taking account of their energy resolution, and we calculate the expected count spectrum of the gamma-ray signal. Then, we employ the ${chi}$-squared test in order to judge the count spectrum contains the LKP signal or not. We can set some constraints on the boost factor which is an uncertain factor dependent on substructure of the LKP distribution in the Galactic halo, if the signal is not detected. If the signal consistent with the peak structure is detected in the future, it will be a conclusive evidence that the dark matter is made of LKP.