A new ultra-sensitive detector sets out to conquer dark matter

This device will try to unlock one of the most tenacious secrets of cosmology.

Among all the mysterious concepts that still torture astrophysicists, dark matter is certainly one of the most iconic. This category of matter occupies a very important place in science fiction and the collective imagination, but it is also at the center of many hypotheses on the dynamics of the cosmos; specialists estimate that it could represent between 20 and 85% of the total matter of the universe.

Despite its capital importance in these models, technically, it remains hypothetical ; so far, no one has been able to provide direct proof. And it’s not for lack of trying; more than 50 state-of-the-art experiments have already tried it.

So far, only the DAMA/LIBRA detector has produced interesting results. But their interpretation remains subject to debate; it is therefore not yet the long-awaited irrefutable proof. On the other hand, this could well happen with the start-up of LUX-ZEPLIN (LZ).

A “onion” ultra-sensitive to detect dark matter

This is an ultra-sensitive detector built by Sanford University that will track down dark matter with unprecedented precision. Physically, it takes the form of several vats of liquid xenon stacked inside each other, much like a Russian doll. In practice, ” the LZ is an onion explains Hugh Lippincott, one of the project leaders at the University of Santa Barbara.

Given enough time and luck, a particle of dark matter could hit a xenon atom by chance. According to the models, this small nanometric cannonball would have the effect of tearing electrons from the nucleus of the atom. This impact would then produce a tiny signal electromagnetic that the researchers hope to measure with their new machine, 100 times more sensitive than its predecessor.

We are looking for a signal that corresponds to a very, very low energy, even by the standards of particle physics. “, explained Lippincott during a press conference. ” This is an extremely rare process, assuming it is visible “, he specifies.

The hunt for WIMPs can begin

And this quest is all the more complicated because scientists have no idea what shape these dark matter particles could take. An uncertainty that forces them to choose the model that seems to them the most promising while accepting the risk of betting on a sterile approach.

In the case of the LZ, they set aside approaches based on dark photons or axions. Instead, they focused on the WIMP model (for Weakly Interacting Massive Particle). These are hypothetical particles that have a certain mass, but do not interact with normal matter, which could help explain their discretion.

Just recently, the machine completed its first 60-day operational sequence. She detected 335 signals judged “ promising » by specialists. In the end, none of them betrayed the presence of a WIMP. But it’s still a big step in that direction.

A simulation of the distribution of dark matter in the Universe. © Springel et al. via CERN

Moving forward despite doubts

Indeed, for work at this exploratory point, looking for a specific object is not yet a viable approach. The interest of this work is that it allows us to refine the work by proceeding by elimination; each time they come across a signal that does not correspond to a WIMP, the researchers can have a more precise idea of ​​the track to follow.

After this first attempt, the LZ will finally get down to business. According to Gizmodo, it will now track alien particles for about three years; enough to collect thousands of signals which, ideally, will end up betraying the presence of a WIMP… assuming that it is indeed the support of dark matter, which is anything but guaranteed.

But despite this artistic vagueness, the game is worth the candle. The discovery of this material would certainly be a major step in the history of science. And this is not an exaggeration.

This would make it possible to make incredible progress on current cosmological models. Enough to open the door to a whole new era of fundamental physics; in other words, there is already a Nobel Prize waiting for the first researchers to prove the existence of dark matter. The future will tell us if it will end up in the wallet of the fathers of LUX-ZEPLIN!

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