Lucca Radicce Justino

arXiv2026

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

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.

hep-ph↗

arXiv2026

Self-resonant dark matter with $Z_4$ gauged symmetry

We present a new model for two-component scalar dark matter (DM), consisting of two complex scalar fields. In this model, both the DM components are stable due to the remaining $Z_4$ gauge symmetry, which is the remnant of the $U(1)^\prime$ local symmetry. When the resonance condition for DM masses is fulfilled, we show that the elastic co-scattering processes between two components of dark matter ($u$-channel processes) are enhanced due to the Yukawa potential with a small effective mass for the lighter DM mediator, so we can use such co-scattering processes for dark matter to explain the small-scale problems at galaxies. Moreover, there are also semi-annihilation processes that two components of dark matter annihilate into one dark matter particle and a dark photon/Higgs, which are enhanced by the $u$-channel Sommerfeld factor. Focusing on some benchmark models for two-component dark matter satisfying the observed relic density, we obtain the bounds for the dark photon portal couplings from the direct detection for boosted dark matter, which is produced from the semi-annihilation processes at the galactic center.

hep-ph↗