In the quest to detect dark matter, a mysterious form of matter that does not interact with light, scientists worldwide have been working tirelessly. As dark matter doesn't directly emit, absorb, or reflect light, its detection poses a significant challenge. Researchers are therefore focusing on signals that may arise from its interactions with other particles in its vicinity.
One of the leading experiments dedicated to this search is PandaX, which utilizes the Particle and Astrophysical Xenon Detector at the China Jinping Underground Laboratory. Recently, the PandaX collaboration published their latest findings in Physical Review Letters, concentrating on the search for light dark matter, specifically weakly interacting massive particles with masses below 1 GeV.
Existing constraints on heavy dark matter candidates are strong, derived from previous direct detection experiments using xenon detectors. However, traditional approaches lack sensitivity when it comes to light dark matter due to the energy threshold for detection. The researchers at PandaX tackled this challenge by focusing on the ionization signal (S2) in dual-phase xenon detectors, which can reduce the energy threshold significantly.
The ionization signal (S2) is amplified in the high electric field in the gas xenon region, allowing researchers to relax the requirement of the prompt scintillation signal (S1). They collected around 90 days of data during the PandaX-4T commissioning run and analyzed the ionization-only data to search for light mass dark matter signals. Although no significant excess was observed, the team managed to set more stringent constraints on the detection of light dark matter through ionization signals.
The new constraints delineate potential mass ranges for different types of dark matter interactions. The limits obtained close in on the parameter space predicted for dark matter particles produced by freeze-in and freeze-out mechanisms in the early universe. This marks a significant step forward, as it's the first time ionization-only backgrounds have been understood and modeled in modern liquid xenon time projection chambers.
With these improved constraints, researchers can now conduct new searches for light dark matter using data from dual-phase xenon detectors. The PandaX experiment continues to collect more data with lower background levels, enabling increasingly stringent constraints on light dark matter. This progress brings us closer to potentially detecting this elusive form of matter in the future.
Moving forward, the PandaX collaboration plans to further suppress ionization-only backgrounds by developing better discrimination algorithms and optimizing running conditions with additional collected data. As the PandaX detector continues its mission, there is hope that it will ultimately contribute to the breakthrough detection of light dark matter.