Gateway to a parallel world? Neutrons (yellow) are confined in this neutron trap by a magnetic field created by superconducting magnets.(Credit: P. R. Huffman et al./Nature)
“An anomaly in the behavior of neutrons may point to the existence of mirror neutrons that could be candidates for dark matter responsible for the missing mass of the universe.
Theoretical physicists Zurab Berezhiani and Fabrizio Nesti from the University of l’Aquila, Italy hypothesized the existence of mirror particles to explain the anomalous loss of neutrons observed experimentally in a neutron trap. The existence of such mirror matter had been suggested in various scientific contexts some time ago, including the search for suitable dark matter candidates.
They re-analysed the experimental data obtained by the research group of Anatoly Serebrov at the Institut Laue-Langevin, France. It showed that the loss rate of very slow free neutrons appeared to depend on the direction and strength of the magnetic field applied. This anomaly could not be explained by known physics.”
More here & here, as well.