According to a new study published in Physical examination letters.
Magnets are intimately familiar to everyone, with many applications in everyday life, from televisions and computers to children’s toys. However, breaking any magnet, such as a navigational compass needle consisting of north and south poles in half, will result in just two smaller bipolar magnets. This mystery has eluded researchers for decades since 1931, when physicist Paul Dirac theorized the existence of unipolar “magnetic monopoles” – particles comparable to electrons but with a magnetic charge.
To determine if magnetic monopoles exist, an international team of researchers, including Volodymyr Takhistov, a member of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) at the University of Tokyo, studied available data from a variety of Earth experiments and performed the most sensitive research to date for monopoles over a wide range of possible masses. The researchers focused on an unusual source of monopoles – atmospheric collisions of cosmic rays that have been happening for eons.
The interdisciplinary research required bringing together expertise from several distinct scientific fields, including accelerator physics, neutrino interactions and cosmic rays.
The collisions of cosmic rays with the atmosphere have already played a central role in the advancement of science, in particular the exploration of ghostly neutrinos. This led to Kavli IPMU Senior Fellow Takaaki Kajita’s 2015 Nobel Prize in Physics for the discovery by the Super-Kamiokande experiment that neutrinos oscillate in flight, implying that they have mass.
Partially inspired by the Super-Kamiokande results, the team set to work on the monopoles. Lightweight monopoles with masses around the electroweak scale, which can be easily accessed by conventional particle accelerators, were particularly intriguing.
By performing simulations of cosmic ray collisions, analogous to particle collisions at CERN’s LHC, the researchers obtained a persistent beam of light monopoles raining down on different experiments on Earth.
This unique source of monopoles is particularly interesting, as it is independent of any pre-existing monopoles such as those potentially left as relics from the early Universe, and covers a wide range of energies.
By reanalyzing data from a wide range of previous experimental monopole searches, the researchers identified new limits on monopoles over a wide range of masses, including those beyond the reach of conventional collider monopole searches. .
These results and the source of monopoles studied by the researchers will serve as a useful reference for interpreting future monopole research in terrestrial laboratories.