Researchers have pioneered a new way to search for dark matter at the ATLAS experiment at CERN.
Dark matter’s existence is a long-standing puzzle in our Universe. Although it makes up a quarter of our Universe, it does not significantly interact with ordinary matter. The search for dark matter, therefore, is highly important.
Dark matter’s existence has been confirmed by several astrophysical observations, but so far, no observation of dark matter has been reported.
Professor Deepak Kar, from the School of Physics at the University of the Witwatersrand in Johannesburg, said: “This is the reason we do research in basic science, probing the deepest mysteries of the Universe.
“The Large Hadron Collider at CERN is the largest experiment ever built, and particle collisions creating big-bang-like conditions can be exploited to look for hints of dark matter.”
Now, Kar and his former PhD student Sukanya Sinha, have developed a new way of searching for dark matter.
The research, ‘Search for non-resonant production of semi-visible jets using Run 2 data in ATLAS,’ has been published in the journal Physics Letters B.
The exploration of a new detector signature
“There has been a plethora of collider searches for dark matter over the past few decades so far have focused on weakly interacting massive particles, termed WIMPs,” said Kar.
“WIMPS is one class of particles that are hypothesised to explain dark matter as they do not absorb or emit light and don’t interact strongly with other particles.
“However, as no evidence of WIMPS’ has been found so far, we realised that the search for dark matter needed a paradigm shift.
“What we were wondering, was whether dark matter particles actually are produced inside a jet of standard model particles,” said Kar.
This led to the exploration of a new detector signature which scientists never looked at before – semi-visible jets.
The new way to search for dark matter inspires further study
High energy collisions of protons result in the production of the collimated spray of particles, collected in the jets. Semi-visible jets arise when dark quarks partially decay to Standard Model quarks and stable dark hadrons.
As they are produced in pairs, along with additional Standard Model jets, the imbalance of energy or the missing energy in the detector arises when all the jets are not fully balanced.
Often, the direction of the missing energy is aligned with one of the semi-visible jets.
The search for semi-visible jets is very challenging. This is because the event signature can arise due to mis-measured jets in the detector.
The new way to search for dark matter opens up new possibilities to validate its existence.
Sinha concluded: “Even though my PhD thesis does not contain a discovery of dark matter, it sets the first and rather stringent upper bounds on this production mode, and already inspiring further studies.”
