[Research Highlight] Neutrino Detector Pursuing Sub-GeV Dark Matter
The Super-Kamiokande Collaboration has searched for light-mass darkmatter accelerated by galactic cosmic rays and published the results in a paper. The paper was published as an “Editor’s Suggestion” in Physical Review Letters.
This paper presents the most stringent constraint on dark matter-hadron coupling at sub-GeV dark matter mass. Surprisingly, the result comes from Super-Kamiokande, a neutrino detector. Due to the higher detection threshold, a neutrino detector is usually not directly sensitive to cold dark matter. However, dark matter can be accelerated above the threshold by collisions with cosmic rays. When traveling through the 20 kilotons of water at the Super-Kamiokande detector, the accelerated dark matter can scatter with protons and leave them recoiling. We searched for an excess of recoil protons from the direction of the galactic center, where most accelerated dark matter comes from. This search is highly sensitive because of the large volume of the Super-Kamiokande and its ability to reconstruct direction. In the absence of an excess, we derived limits on the dark matter-hadron interaction and ruled out a large parameter space previously unexplored.