Probing the Dark Sector with Nuclear Transition Photons.

Area of Science:

• Particle Physics
• Cosmology
• Nuclear Physics

Background:

• Dark matter (DM) remains undetected, motivating new experimental searches.
• Beam-dump experiments offer a unique window into dark sector physics.
• Existing DM detection methods often rely on elastic scattering.

Purpose of the Study:

• To present world-leading sensitivity to light dark matter (<170 MeV) using beam-dump experiments.
• To explore the potential of nuclear de-excitation via inelastic dark matter scattering for detection.
• To set stringent constraints on dark matter models, particularly the dark-photon portal.

Main Methods:

• Utilizing data from the historical KARMEN experiment.
• Analyzing signals from nuclear de-excitation following inelastic dark matter scattering.
• Comparing sensitivity with traditional elastic scattering channels.

Main Results:

• Achieved world-leading sensitivity to light dark matter (<170 MeV).
• Demonstrated sensitivity to the thermal relic abundance benchmark for scalar dark matter in a dark-photon portal model.
• Set world-leading constraints on this dark matter model using archival data.

Conclusions:

• The nuclear de-excitation channel offers superior sensitivity for dark matter detection compared to elastic scattering.
• The KARMEN experiment's data provides powerful constraints on light dark matter models.
• Future experiments with planned improvements can extend this technique to probe fermionic dark matter.