Constraints on the Inert Doublet Model of dark matter with very high-energy gamma-ray observatories

Abstract

We investigate constraints on the Inert Doublet Model (IDM) that features a scalar dark matter candidate, using data from recent and future gamma-ray observatories. The relevance of the model for indirect searches of dark matter stems from two key features: first, in the high mass regime, IDM can achieve the correct dark matter relic abundance for masses between approximately 500 GeV and 25 TeV, aligning perfectly with the energy sensitivity of Imaging Atmospheric Cherenkov Telescopes. Second, this regime is dominated by co-annihilation processes, which elevate the thermal relic velocity-weighted annihilation cross section to the range of $0.5$ to $1.0\times 10^{-25}$ cm${}^3$ s${}^{-1}$, thereby enhancing the potential gamma-ray signal from dark matter annihilation. Analyzing the recent H.E.S.S. Inner Galaxy Survey, we find that dark matter particle masses within the 1-8 TeV range are excluded by current data, assuming a benchmark cuspy Einasto profile. Furthermore, we project that the Cherenkov Telescope Array Observatory (CTAO) will comprehensively probe the remaining viable parameter space of the IDM under the same assumptions. Our findings are further examined in light of recent theoretical constraints, collider searches, and direct detection results from the LUX-ZEPLIN experiment.

Comments: 13 pages, 6 figures. Matches the version published in PLB