31. July 2026
(CONNECT) Researchers from the Paul Scherrer Institute (PSI) in Villigen in the canton of Aargau, Switzerland, the Swiss Federal Institute of Technology in Zurich (ETH) and Jagiellonian University in Kraków conducted experiments to investigate whether elementary particles can potentially disappear into a corresponding mirror world. According to a hypothesis in theoretical physics, the elementary particles in this mirror world were cited as potential candidates for what is known as dark matter in the universe. However, based on the latest findings, the researchers have now been able to rule out such a theory with a probability of 99.98 percent, according to a statement.
In their experiment, the researchers used neutral elementary particles in the form of ultra-cold neutrons cooled to approximately 1.8 Kelvin. “There is no way of proving the existence of mirror particles using gravitational interaction alone”, as Bernhard Lauss, leader of the research group for ultracold neutron physics at the PSI Center for Neutron and Muon Sciences, adding that: “Because of this, we focused on the other properties of mirror particles, namely that, based on this hypothesis, neutral particles might oscillate to and fro between our normal matter world and the mirror world”.
In an attempt to prove this, around 1.5 million neutrons were stored in a in a special, non-magnetic stainless-steel vacuum tank every five minutes. After about 200 seconds each time, the container was emptied, and the researchers determined how many neutrons were left over in a process that was repeated across a time frame of several months. In the end, around 25 billion neutrons were measured in total. Based on the measurements, it was ruled out with 99.98 percent certainty that neutrons can oscillate in a “mirror world”. Ultimately, these findings imply that either such a mirror world does not exist or neutral particles cannot overcome a barrier. As such, this latest study casts doubt on the theory of a mirror world. “By restricting the scope for certain speculations, we are showing researchers in theoretical physics that they need to explore new avenues”, comments Geza Zsigmond, senior author of the study, which was recently published in ‘Physical Review Letters’, concluding that: “Physics needs that kind of impetus if it is to continue to evolve”. ce/eb
