CERN researchers continue to look for elusive monopoles

New advances were made from LHC Run 2 data obtained between 2015 and 2018 but the scientists are yet to spot the monopoles.
Ameya Paleja
Illustration of magnetic monopoles (larger image) and a magnetic dipole (inset) (
Illustration of magnetic monopoles (larger image) and a magnetic dipole (inset) (


Researchers at the European Council for Nuclear Research (CERN) are among those physicists who have been looking for magnetic monopoles. A recently published paper from the ATLAS Collaboration at CERN has confirmed that it continues to look for the elusive particle, a press release said.

The ATLAS Collaboration is one of science's most significant collaborative efforts. Its webpage states that it consists of 000 members and 3,000 scientific authors comprised of physicists, engineers, technicians, students, and support staff from around the world.

ATLAS is the largest general-purpose particle detector at the Large Hadron Collider (LHC) at CERN and is tasked with detecting phenomena that have previously not been observed. The collaboration was instrumental in discovering the Higgs boson and has focused on the elusive magnetic monopole.

What is a magnetic monopole?

It is common knowledge that magnets have two poles, a north and a south. These poles are maintained even if an appeal is broken into two parts, irrespective of the size of the broken parts.

Nearly a century ago, physicist Paul Dirac proved that magnetic monopoles, where the magnet has only one pole, north or south, are consistent with quantum mechanics and require quantization of electric charge. More theories that arose in the 1970s predicted that magnetic monopoles were part of the fundamental forces of nature.

Scientists also suggest that magnetic monopoles might have been present in the early Universe but were diluted as the Universe expanded exponentially in its early phase. Researchers at ATLAS have, therefore, been working to spot magnetic monopoles in the LHC data.

Looking for monopoles

The strategy adopted by ATLAS relies on Dirac's theory, which states that the magnitude of the minor magnetic charge (gD) is equivalent to 68.5 times the fundamental unit of electric charge or the charge of the electron (e). Therefore, a magnetic monopole of charge  1gD would ionize matter in a way similar to a high-electric-charge object (HECO).

CERN researchers continue to look for elusive monopoles
Image of a section of CERN's tunnel for the LHC

When any particle ionizes in the LHC, ATLAS can detect the energy, which is proportional to the square of the particle's charge. The researchers are, therefore, confident that even magnetic monopoles would leave large energy deposits along their trajectors in the detector.

The ATLAS team has been looking for pairs of magnetic monopoles with masses of about four teraelectronvolts (TeV). The researchers suggest that this can happen with either of the mechanisms between photons in 13 TeV collisions. A virtual photon created in the collision produces a monopole, or two virtual photons radiated by protons interact to produce monopoles.

Researchers then combed through the entire dataset of LHC Run 2, which occurred similarly between 2015-2018, looking for signs of monopoles and HECOs. The team placed tight limits on what could be considered a magnetic monopole as it looked for charges 1gD and 2gD and HECOs of charge 20e, 40e, 60e, 80e, and 100e, with masses between 0.2 TeV and 4 TeV, the press release said.

This was also the first time the researchers used a photo-fusion mechanism for monopole production. However, the team did not find evidence for magnetic monopoles and are now looking to revise their strategies as they also analyze data from Run 3.