East Asia's Quiet Race to Find the Universe’s Missing Mass

In the global quest to directly detect dark matter, the invisible substance thought to constitute roughly 25 percent of the universe, East Asian nations are rapidly increasing their prominence. China, South Korea, and Japan are each pursuing independent programs, with some operating experiments that boast world-leading sensitivity. While dark matter's existence is inferred from phenomena like galactic rotation speeds and gravitational lensing, it has never been directly observed. Alongside prominent Western experiments such as LUX-ZEPLIN (LZ) in the United States, XENONnT in Europe, and DarkSide-20k in Italy, scientists in East Asia are playing a crucial role in unraveling this mystery. China's dark matter exploration is anchored at the China Jinping Underground Laboratory (CJPL) in Sichuan Province, utilizing the world's deepest underground laboratory. Its flagship experiment, PandaX-4T, employing a liquid xenon detector, has set the tightest limits yet on dark matter particles of specific masses. Additionally, China is pursuing the CDEX experiment to search for lighter dark matter candidates and conducting satellite observations of cosmic-ray electrons and positrons. South Korea, aiming to verify the annual modulation signal claimed by Italy's DAMA/LIBRA experiment—a long-standing puzzle—conducted the COSINE-100 experiment at the Yangyang Underground Laboratory. This experiment, using the same technology as DAMA/LIBRA, yielded results that disfavor the presence of an annual modulation signal, serving as a clear example of an Asian experiment resolving a decades-old controversy in the field. Japan, through the Institute for Cosmic Ray Research at the University of Tokyo, has a long history of contributions to underground physics at the Kamioka Observatory. In recent years, focus has shifted to directional detection experiments like NEWAGE, which aim to pinpoint the direction of dark matter's arrival. The collaboration is proceeding with the installation and commissioning of new detector modules. These endeavors by East Asian countries underscore the importance of international collaboration in solving the fundamental mystery of dark matter and are expected to make significant contributions to future scientific discoveries.