Scientists invent a way to trap a mysterious particle of the "dark world" at the large Hadron Collider

Now that they have identified the Higgs boson, the scientists at the Large Hadron Collider have moved towards an even harder target to reach.

All around us there is dark matter and black energy – the invisible substance that binds the galaxy together, but no one has been able to detect it directly. "We know for sure that the world is dark and that it contains more energy than ours," said LianTao Wang, professor of physics at the University of Chicago, who is studying how to find signals in large particle accelerators such as the LHC.

Wang, along with UChicago-affiliated scientists from the University and Fermilab, think they could lead us on his heels. in an article published on April 3 in Letters of physical examination, they presented an innovative method to track dark matter in the LHC by exploiting the slightly slower speed of a potential particle.

While the world of darkness represents more than 95% of the universe, scientists know that it exists through its effects – as a poltergeist, you can only see it when it is pushing back something from a shelf. For example, we know that there is dark matter because we can see gravity acting on it – it prevents our galaxies from shattering.

Theorists believe that there is a particular type of dark particle that interacts only occasionally with normal matter. It would be heavier and last longer than other known particles, with a lifespan of up to one tenth of a second. The researchers believe that this particle can be caught in proton collisions that the LHC creates and measures constantly.

"A particularly interesting possibility is that these long-lived dark particles are coupled in one way or another to the Higgs boson – that they are actually a gateway to the dark world." Wang said, referring to the last particle of the great theory of physicists. of the operation of the universe, discovered at the LHC in 2012. "It is possible that the Higgs break down into these long-lived particles."

The only problem is to sort these events among the rest; There is more than a billion collisions per second in the LHC, of ​​a length of 27 km, and each of them sends a subatomic spraying of glitter in all directions.

Wang, Jia Liu, a postdoctoral researcher at UChicago, and Zhen Liu, a scientist at Fermilab (now at the University of Maryland), have proposed a new way of looking at exploiting a particular aspect of such a dark particle. "If it is so heavy, its production costs energy, so its momentum would not be important: it would move more slowly than the speed of light," said Liu, the first author of the paper. 39; study.

This delay would differentiate it from the rest of the normal particles. Scientists would only need to adjust the system to look for the particles produced then disintegrate a little slower than anything else.

The difference is in the order of a nanosecond – a billionth of a second – or less. But the LHC already has enough sophisticated detectors to detect this difference. A recent study using the data collected in the last analysis revealed that the method should work and that detectors will become even more sensitive as part of the ongoing upgrade.

"We expect this method to increase our sensitivity to long-lived dark particles by more than an order of magnitude, while using the capabilities we already have at the LHC," said Liu.

The experimenters are already working on the construction of the trap: when the LHC will reignite in 2021, after having increased tenfold, the three main detectors will implement the new system, the scientists announced. "We think it has great potential for discovery," Liu said.

"If the particle is there, we just have to find a way to unearth it," Wang said. "Usually the key is to find the question to ask."