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

Abstract

The lightest Kaluza-Klein particle (LKP), which appears in the theory of universal extra dimensions, is one of the good candidates for cold dark matter. The gamma-ray spectrum from annihilation of LKP dark matter shows a characteristic peak structure around the LKP mass. We investigate the detectability of this peak structure by considering energy resolution of near-future detectors, and calculate the expected count spectrum of the gamma-ray signal. In order to judge whether the count spectrum contains the LKP signal, the {\chi} squared test is employed. If the signal is not detected, we set some constraints on the boost factor that is an uncertain factor dependent on the substructure of the LKP distribution in the galactic halo. Detecting such peak structure would be conclusive evidence that dark matter is made of LKP.