Encirclement of long-awaited magnetic monopoles in an LHC experiment

An international research group, in which the Corpuscular Physics Institute (IFIC, a mixed center of the CSIC and the University of Valencia) participates, has taken a giant step forward in the experimental search for magnetic monopoles, hypothetical elementary particles predicted by various theories but not yet observed.

To do this, they have explored a mechanism for the production of matter proposed by the American physicist Julian Schwinger, winner of the Nobel Prize in 1965. The results of the study have been published in the journal Nature.

The MoEDAL experiment reports on how to look for the production of magnetic monopoles by heavy lead ion collisions at the LHC, producing the strongest magnetic fields in the universe.

“We present a search for the production of magnetic monopoles by the Schwinger mechanism in heavy lead ion collisions at the Large Hadron Collider (LHC), producing the strongest known magnetic fields in the universe today,” the authors note.

Within the LHC of the European Particle Physics Laboratory (CERN, on the French-Swiss border), the research is carried out specifically in the Monopole and Exotics Detector (MoEDAL) experiment, whose main objective is the direct search for magnetic monopoles and other particles exotic.

As their name suggests, these particles are characterized by having a single magnetic pole, a peculiar property never before observed. Confirming its existence would be transformative for physics, since it would open a new path beyond the Standard Model, the currently accepted theory to describe the microscopic world, and symmetrize the Maxwell equations, which describe the laws of electromagnetism.

Vasiliki Mitsou, a researcher at the Institute of Corpuscular Physics and leader of the MoEDAL group in Valencia, is also the analysis coordinator for the aforementioned experiment. She has led all the steps to obtain these new results and has been one of the internal reviewers of the collaboration article.

“The synergy between experimental and theoretical physicists at MoEDAL has enabled, for the first time, the search for finite-size monopoles, also inaugurating the use of the powerful magnetic field present in heavy ion collisions at the LHC. This Schwinger mechanism makes it possible to calculate physically valid monopole production probabilities,” says Mitsou.

The largest and most powerful accelerator in the world, the LHC

The experiment looks for the production of magnetic monopoles in heavy ion collisions at the world’s largest and most powerful particle accelerator, the LHC. The collisions generate strong magnetic fields, which could give rise to the spontaneous creation of magnetic monopoles through the Schwinger mechanism (phenomenon by which matter is created by a strong electric field).

To detect magnetic monopoles, MoEDAL researchers have used a superconducting magnetometer to scan detector modules exposed to the LHC’s lead-lead collisions for signs of trapped magnetic charge.

Since no such signal was found, the researchers were able to exclude the existence of monopoles with mass less than 75 gigaelectronvolts (GeV), for magnetic charges ranging from 1 to 3 base units of magnetic charge.

The experiment plans to take more data and increase its sensitivity to detect heavier, more magnetically charged monopoles in the near future. The MoEDAL collaboration will now use the full MoEDAL detector, including plastic trace detectors in addition to monopole capture detectors, to drive the search for monopoles at higher masses and charges using the full dataset taken over the period 2015- 2018.

In addition, an updated MoEDAL detector will be deployed for data collection in the LHC’s Run-3, which will return to operation from spring 2022.

Reference:

B. Acharya et al. “Search for magnetic monopoles produced via the Schwinger mechanism”. Nature, 2022.

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Encirclement of long-awaited magnetic monopoles in an LHC experiment