An international collaboration of scientists has achieved a significant milestone in the search for dark matter, setting a new benchmark for sensitivity in detecting light dark matter particles. The QROCODILE experiment, led by researchers from the University of Zurich and the Hebrew University of Jerusalem, has utilized advanced superconducting detectors cooled to near absolute zero to establish unprecedented limits on the interaction of dark matter with ordinary matter.
Dark matter, estimated to comprise about 85% of the universe's mass, remains one of physics' most profound mysteries. Its elusive nature, characterized by invisibility and lack of interaction with electromagnetic radiation, has made direct detection a formidable challenge for decades. Scientists have long sought to capture even a single particle of this mysterious substance, which plays a crucial role in shaping the structure of galaxies and the cosmos.
The QROCODILE experiment employs a novel approach, focusing on the detection of "light" dark matter particles with masses significantly smaller than those typically investigated in previous experiments. At the core of this research is a state-of-the-art superconducting detector capable of registering incredibly faint energy depositions as low as 0.11 electron-volts. This remarkable sensitivity, millions of times finer than that of conventional particle physics experiments, opens a new frontier for exploring extremely light dark matter candidates.
During a scientific run spanning over 400 hours, the QROCODILE team observed a small number of unexplained signals. While these events require further investigation to rule out origins from cosmic rays or natural background radiation, they have enabled the establishment of new, stringent limits on the interaction strengths of light dark matter particles with both electrons and atomic nuclei. A key advancement highlighted by the experiment is its potential for directional sensitivity, which could help distinguish genuine dark matter signals from background noise.
Professor Yonit Hochberg of the Racah Institute of Physics at the Hebrew University, a lead scientist on the project, stated, "For the first time, we have established new limits on the existence of particularly light dark matter particles. This is an important first step towards larger experiments that could ultimately achieve the long-awaited direct detection." The published results in Physical Review Letters validate the experimental approach and pave the way for future advancements.
The next phase, known as NILE QROCODILE, aims to further enhance the detector's sensitivity and will involve relocating the experiment underground to provide enhanced shielding from cosmic rays. This strategic move is expected to increase the experiment's precision and its prospects for uncovering the secrets of dark matter.