Australian researchers have played a central role in a landmark result from the LUX-ZEPLIN (LZ) experiment in South Dakota—the world’s most sensitive dark matter detector. Today, scientists working on the experiment report they have further narrowed constraints on proposed dark matter particles. And, for the first time, the experiment has detected elusive neutrinos produced deep inside the sun.

Scientists hypothesize that dark matter makes up about a quarter of the universe’s mass (or 85% of its matter) but have yet to detect exactly what makes up this strange phenomenon. The result announced today by the LZ experiment is one of the world’s most sensitive measurements in the hunt for dark matter. It has expanded its search for WIMPs (weakly interacting massive particles) down to masses approximately between that of three and nine times that of a proton, the positively charged particle in the nucleus of an atom.

Dr. Theresa Fruth, from the University of Sydney’s School of Physics, is one of only two Australian-based researchers in the 250-member international collaboration.

Dark matter is an elusive type of matter that does not emit, reflect or absorb light, yet is estimated to account for most of the universe’s mass. Over the past decades, many physicists worldwide have been trying to detect this type of matter or signals associated with its presence, employing various approaches and technologies.

As it has never been directly detected before, the composition and properties of dark matter remain mostly unknown. Initially, dark matter searches focused on the detection of relatively heavy particles. More recently, however, physicists also started looking for lighter particles with masses below one giga-electron-volt (GeV), which would thus be lighter than protons.

Researchers at SLAC National Accelerator Laboratory and The Ohio State University recently showed that signatures of these sub-GeV dark matter particles could also be picked up by neutrino observatories, large underground detectors originally designed to study neutrinos (i.e., light particles that weakly interact with regular matter).

Observations of the formation of light-nuclei from high-energy collisions may help in the hunt for dark matter.

Particle collisions at the Large Hadron Collider (LHC) can reach temperatures over one hundred thousand times hotter than at the center of the sun. Yet, somehow, light atomic nuclei and their antimatter counterparts emerge from this scorching environment unscathed, even though the bonds holding the nuclei together would normally be expected to break at a much lower temperature.

Physicists have puzzled for decades over how this is possible, but now the ALICE collaboration has provided experimental evidence of how it happens, with its results published today in Nature.