Year: 2026
Type: preprint
Abstract: Endothermic upscattering of heavy dark matter offers a compelling interpretation of the high-energy nuclear-recoil candidate recently reported by LUX-ZEPLIN (LZ), with a characteristic recoil energy $E_R \propto δ$, where $δ$ is the mass splitting between the dark matter states. Cosmological and experimental constraints motivate the depletion of the primordial heavier state, which can be regenerated in the Galactic halo. We show that, if the heavier state decays radiatively, the same mass splitting sets the energy of a gamma-ray line, $E_γ\simeq δ$. For our benchmark, this leads to a sub-MeV line within the projected reach of the Compton Spectrometer and Imager (COSI), scheduled for launch in 2027. The confirmation of the LZ candidate event as a dark matter signal would therefore motivate dedicated searches for sub-MeV gamma-ray lines, with COSI providing a timely opportunity to test this interpretation.
Source: arXiv (Cornell University)
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214779481