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Scientists refine the search for dark matter

Researchers from Lund University in Sweden, among others, have developed a more effective technique in the search for clues about dark matter in the universe. They can now analyse much larger amounts of the data generated at CERN.
Researchers.
William Kalderon, Eric Corrigan, Eva Hansen (remotely), Caterina Doglioni, Alexander Ekman. Photo: Lena Björk Blixt.

At the CERN research facility, a long series of experiments is underway on protons colliding in the LHC accelerator at almost the speed of light. The amount of data is constantly increasing, as the accelerator’s capacity improves. However, it is more difficult to process and store the vast amounts of data that are produced. This is why there is a continuous evaluation of which data the researchers should examine more closely.

“If we are not careful, we could end up discarding data that contains clues to completely new particles of which we are not yet aware, such as particles that form dark matter”, explains Caterina Doglioni, a particle physicist at Lund University and a member of the ATLAS experiment at CERN.


She is one of the researchers behind a recent study focusing on how to better utilise CERN’s enormous amounts of data. Instead of recording all the information from the experiment and then analysing it at a later date, much of the data analysis is done in a short amount of time so that a much smaller fraction of the event is retained. This technique, that has been employed by other LHC experiments as well, allows researchers to record and store many more events that could contain traces of new particles.

The hope is to find signs of hitherto unknown particles that could be carriers of forces that could create a connection between visible and dark matter, according to Doglioni.

“These new particles, which we call “mediator particles” can disintegrate into extremely short-lived pairs of quarks, i.e. the very building blocks of the protons and neutrons in atoms. When quarks disintegrate, a type of particle shower is formed that we can actually detect with our instruments”, says Caterina Doglioni.

The research community has long been searching for answers about the elusive dark matter that makes up a large part of our universe. Only five per cent of the universe is matter that we are currently able to perceive and measure. The remaining 95 per cent is unexplored and referred to as dark matter and dark energy.

Among other things, this assumption is based on the fact that galaxies rotate as though there were significantly more matter than that which we can see. Dark matter is reported to make up 27 per cent of the universe, while 68 per cent is dark energy - considered to be what causes the universe to constantly accelerate in its ongoing expansion. Researchers have declared October 31st “Dark Matter Day”, a day with many different events dedicated to dark matter all over the world.

“We know that dark matter exists. Normally it passes through our measurement instruments, but cannot be registered, but in the case of our research we hoped to see the products of particles connected to it. ”, says Caterina Doglioni.

She doesn’t dare to predict how long it might take before there is a breakthrough in the search for dark matter. Meanwhile, Doglioni observes that research initiatives provide spin-off effects as they proceed. Knowledge about how to process these vast amounts of data is also valuable outside the research community, and has led to the launch of various collaborations with industry.

The current study was recently published in the scientific journal Physics Review Letters. The research is funded by the European Research Council, ERC.

Facts about ATLAS

ATLAS is one of CERN’s experiment stations. It is where the accelerator ring’s two proton beams collide at unimaginable energy density. The researchers use the collisions to try to find out more about how matter is structured and what other, unknown particles might exist besides the quarks and other building blocks identified so far – all to contribute to our understanding of the structure of the universe.

The Standard Model and new physics

The Standard Model is the theory (law of nature) that physicists use to describe the world. However, the Standard Model only deals with the matter known to science, and is therefore now considered merely part of a larger theory that describes the world. The insight that most of the universe is instead made up of unknown dark matter and dark energy makes particle physics an even greater adventure, referred to as the search for new physics. In this context, there are many questions that arise: are there more forces besides the four we know? Could there be additional spatial dimensions to the three perceived by humans? And how small are the building blocks that make up the world – is there something smaller than quarks?

Lena Björk Blixt

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