Scientists from the University of Nottingham, working with an international team, have exposed the strictest limitations yet on magnetic monopoles in a study reported in Physical Review Letters, consequently stretching the boundaries of knowledge about these elusive particles.
A new study utilizing a decommissioned portion of the beam pipe from CERN's Large Hadron Collider (LHC) has brought scientists closer than ever to testing the existence of magnetic monopoles.
A hypothetical basic particle known as a "magnetic monopole" in particle physics is an isolated magnet with just one magnetic pole—a north pole devoid of a south pole, or vice versa.
Could there be particles with only a single magnetic pole, either north or south? This intriguing possibility, championed by renowned physicists Pierre Curie, Paul Dirac, and Joseph Polchinski, has remained one of the most captivating mysteries in theoretical physics. Confirming their existence would be transformative for physics, yet to date experimental searches have come up empty-handed.
Oliver Gould, Study Lead Theorist and Dorothy Hodgkin Fellow, School of Physics and Astronomy, University of Nottingham
The search team concentrated on a beam pipe segment decommissioned from the LHC at CERN, the European Organization for Nuclear Research. Scientists from the Monopole and Exotics Detector at the LHC (MoEDAL) experiment examined a beryllium beam pipe segment situated at the particle collision point for the Compact Muon Solenoid (CMS) experiment. The billions of ultra-high-energy ion collisions that were taking place only centimeters away exposed this conduit to radiation.
The search team concentrated on a beam pipe segment decommissioned from the LHC at CERN, the European Organization for Nuclear Research. Scientists from the Monopole and Exotics Detector at the LHC (MoEDAL) experiment examined a beryllium beam pipe section situated near the particle collision point for the Compact Muon Solenoid (CMS) experiment. The billions of ultra-high-energy ion collisions that were taking place only centimeters away exposed this conduit to radiation.
The proximity of the beam pipe to the collision point of ultra-relativistic heavy ions provides a unique opportunity to probe monopoles with unprecedentedly high magnetic charges, since magnetic charge is conserved, the monopoles cannot decay and are expected to get trapped by the pipe's material, which allows us to reliably search for them with a device directly sensitive to magnetic charge.
Aditya Upreti, Ph.D., Department of Physics and Astronomy, University of Alabama
Upreti also led the experimental analysis while working in Professor Ostrovskiy's MoEDAL group.
At the LHC, where heavy ion collisions produce magnetic fields much greater than those of rapidly spinning neutron stars, the researchers studied the creation of magnetic monopoles. The Schwinger process can trigger magnetic monopoles to form spontaneously at such intense fields.
Gould added, “Despite being an old piece of pipe destined for disposal, our predictions indicated it might be the most promising place on Earth to find a magnetic monopole.”
The MoEDAL collaboration scanned the beam pipe using a superconductive magnetometer for signs of trapped magnetic charge. Their results preclude the occurrence of monopoles lighter than 80 GeV/c² (where c is the speed of light) and establish the world’s leading restrictions for magnetic charges ranging from 2 to 45 base units, despite the fact that they did not find any evidence of magnetic monopoles.
Oliver concluded, “The beam pipe that we used was from the first run of the Large Hadron Collider, which was carried out before 2013 and at lower energies. Extending the study to a more recent run at higher energies could double our experimental reach. We are also now considering completely different search strategies for magnetic monopoles.”
Journal Reference:
Acharya, B., et al. (2024) MoEDAL Search in the CMS Beam Pipe for Magnetic Monopoles Produced via the Schwinger Effect. Physical Review Letters. doi.org/10.1103/physrevlett.133.071803.