ATLAS homes in on magnetic monopoles

CERN — ATLAS Experiment logo.

17 June, 2019

The ATLAS collaboration has placed some of the tightest limits yet on the production rate of hypothetical particles known as magnetic monopoles 

Magnetic monopoles (larger image) and magnetic dipole (inset) (Image: CERN)

Break a magnet in two, no matter how small, and you’ll get two magnets, each with a south and a north pole of opposite magnetic nature. However, some theories predict particles with an isolated magnetic pole, which would carry a magnetic charge analogous to a positive or negative electric charge. But despite many searches, such magnetic monopoles have never been spotted at particle colliders. A new search by the ATLAS collaboration at CERN places some of the tightest bounds yet on the production rate of these hypothetical particles. These results are complementary to those from CERN’s MoEDAL experiment, which is specifically designed to search for magnetic monopoles.

Originally proposed in 1931 by physicist Paul Dirac, magnetic monopoles have since been shown to be an outcome of so-called grand unified theories (GUTs) of particle physics, which connect fundamental forces at high energies into a single force. Such GUT monopoles typically have masses that are too high for them to be spotted at particle colliders, but some extensions of the Standard Model predict monopoles with masses that could be in a range accessible to colliders.

The latest ATLAS search is based on data from proton–proton collisions produced at the Large Hadron Collider at an energy of 13 TeV. The collaboration looked for signs in the data of large energy deposits that would be left behind by the magnetic monopoles in the ATLAS particle detector. The energy deposits would be proportional to their magnetic charge squared. Such large deposits are also an expected signature of high-electric-charge objects (HECOs), which may include mini black holes, so the search was also sensitive to HECOs.

The team found no sign of magnetic monopoles or HECOs in the data but improved previous work on several fronts. Firstly, the search achieves improved limits on the production rate of monopoles that carry one or two units of a fundamental magnetic charge called Dirac charge. The new limits surpass those from MoEDAL, although MoEDAL is sensitive to a larger range of magnetic charge – up to five Dirac charges – and can probe monopoles produced by two mechanisms, whereas ATLAS probed only one. MoEDAL researchers are also working towards pushing the experiment to probe monopoles with magnetic charges well beyond five Dirac charges.

In addition, the ATLAS search improves limits on the production of HECOs with electric charge between 20 and 60 times the charge of the electron. Finally, the search is the first to probe HECOs with charges greater than 60 times the electron charge, surpassing the charge probed by previous searches by ATLAS and also by the CMS collaboration.

For more information about these results, see the ATLAS website: https://atlas.cern/updates/physics-briefing/new-result-magnetic-monopoles

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 23 Member States.

Related links:

ATLAS collaboration: https://atlas.cern/

MoEDAL experiment: https://home.cern/science/experiments/moedal

Standard Model: https://home.cern/science/physics/standard-model

Large Hadron Collider (LHC): https://home.cern/science/accelerators/large-hadron-collider

CMS collaboration: https://cms.cern/

For more information about European Organization for Nuclear Research (CERN), Visit: https://home.cern/

Image (mentioned), Text, Credits: CERN/ Ana Lopes.

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