Dark Matter Search: New Horizons and Challenges for Physicists

Dark matter is one of the most intriguing mysteries in modern science. Its existence is confirmed by gravitational effects: for example, the Milky Way’s rotation speed around the galactic center is too high to be explained by visible matter alone. Without the additional mass provided by dark matter, the Solar System would have long since escaped the galaxy’s boundaries. Yet its true nature remains unknown.

For decades, WIMPs (weakly interacting massive particles) were the leading candidate for dark matter. The idea emerged in the 1980s within supersymmetry theories, which proposed 'superpartners' for known particles. WIMPs were expected to have significant mass and interact weakly with ordinary matter, making them ideal candidates. However, experiments at the Large Hadron Collider (LHC) failed to validate these theories, and detectors like LZ and PandaX-4T have yet to detect WIMPs.

New challenges complicate the search further. Neutrino interactions with detector materials create interference—the so-called 'neutrino fog'—which masks potential WIMP signals. The XLZD project, once poised to be the final major WIMP search experiment, now faces financial hurdles after the U.S. Department of Energy withdrew funding, threatening its realization.

In response, researchers are broadening their hypotheses. Alternatives include primordial black holes, formed shortly after the Big Bang, and other exotic particles. The possible mass range for dark matter candidates spans 50 orders of magnitude, making the search even more daunting. Despite setbacks, scientists remain driven by the unyielding motivation to unravel dark matter’s nature.