Magnetic Monopoles in the Universe fewer than Expected

2022-02-03

Uppsala researchers and IceCube-members Alexander Burgman and Carlos de los Heros have, based on data from the IceCube-telescope on the South Pole, searched for a cosmic flux of magnetic monopoles with speeds near the speed of light. But they have not detected any, which means that the number of monopoles in the universe is fewer than previously thought.

According to current theories that describe the properties and interactions of subatomic particles, such as electrons and protons, they might, in addition to an electric charge, also have a magnetic charge. These particles are called magnetic monopoles and they should have been produced at the same time as all other matter in the early evolution of the universe. Since they are predicted to be stable, the flux of magnetic monopoles created in the young universe should permeate all space even today. But the problem is that they have never been detected.

Cherenkov light
Artistic illustration of what it might look like if magnetic monopoles would be detected in the IceCube-telescope. The blue colour represents the so called Cherenkov light that charged particles emit when crossing the IceCube-detector in the same way that magnetic monopoles would do. But a monopole would emit much stronger light. Image: Nicolle R. Fuller/NSF/IceCube.

With the help of the gigantic neutrino telescope IceCube on the South Pole, which foremost is used to detect neutrinos, but also can detect magnetic monopoles that pass through it, Alexander Burgman and his supervisor Carlos de los Heros have searched for a cosmic flux of magnetic monopoles at speeds near the speed of light.

The researchers have in their search for magnetic monopoles analysed eight years of data and made use of a machine learning technique to be able to differentiate potential monopoles from the much more frequent neutrinos that IceCube detects all the time.

IceCube Laboratory at the South Pole
The IceCube-laboratory on the South Pole. Particles are detected by 5000 light sensors in the IceCube-telescope which are buried between 1.5 and 2.5 kilometers under the ice. Image: Martin Wolf, IceCube/NSF.

But they have not detected any monopoles. The results from the IceCube measurement mean that the upper limit of the number of monopoles in the universe has been lowered by a factor 10. This new limit on the flux of magnetic monopoles is world-leading and it can be interpreted as that there is less than one monopole in space in a volume corresponding to the size of the Earth.

Further data analyses during a longer period of time will give even more accurate results to determine the number of magnetic monopoles in the universe. In present models of the early universe, it is assumed that there are magnetic monopoles. If it should turn out that they do not exist, basic assumptions in our understanding of the evolution of the universe may need to be reconsidered.

Article Reference

R. Abbasi et al. (IceCube Collaboration), Search for Relativistic Magnetic Monopoles with Eight Years of IceCube Data, Phys. Rev. Lett. 128, 051101. Publicerad 2 februari 2022, DOI: 10.1103/PhysRevLett.128.051101

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The result has also been mentioned by American Physical Society on their news page.

Contact

Carlos de los Heros, Senior Lecturer/Associate Professor at the Division of High Energy Physics at the Department of Physics and Astronomy, carlos.de-los-heros@physics.uu.se. +46 18-471 3256.

Camilla Thulin

English translation: Johan Wall

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