In an abandoned gold mine one mile from Leed, South Dakota, engineers and physicists at the University of Wisconsin-Madison are working on a chamber containing 10 tons of liquid xenon. They hope that in an underground mine, where the experimental space will be protected from solar particles and cosmic radiation, they will be able to detect dark matter for the first time.
We have already published a detailed analysis of what mysterious dark matter can be from the point of view of modern physics. The initial hypothesis appeared back in the 1930s, when astronomers realized that the galaxy lacks the force of gravity in order to maintain its structure only due to its visible sources - stars, planets, black holes, etc. Directly the dark matter itself before so far it has not been possible to detect, its existence was deduced only with the help of gravitational mathematical models. However, astronomers believe that in fact, there may be five times more dark matter in the universe than visible matter. The UW-Madison team has decided to end this uncertainty.
The South Dakota gold mine experiment is called LUX-ZEPLIN, or LZ for short. It is an extended version of the previous Large Underground Xenon (LUX) experiment and the ZEPLIN dark matter program. The idea is to detect a dark matter particle as it interacts with a xenon atom, causing a chain reaction in the chamber that will eventually eject ultraviolet light and release a barrage of electrons. Immediately after the liquid xenon ignites, the xenon gas in the chamber above it will react by emitting electrons and release a second, brighter pulse of light. Physicists working on the project describe it as a "bell" that will ring when exposed to a particle of dark matter.
“Dark matter particles can be right here in the room, passing through your head and possibly occasionally colliding with some atoms,” Duncan Carlsmith, professor of physics at UW-Madison, said in a press release.
Schematic representation of the LUX-ZEPLIN underground laboratory
Earlier this month, the Department of Energy approved the final stages of the LZ at the gold mine, officially named the Sanford Underground Research Center. Meanwhile, researchers are working with a smaller prototype device to ensure that when the "big" LZ launches in 2020, it won't be susceptible to interference.
To ensure that nothing but dark matter interacts with liquid xenon, the team is building two external chambers designed to detect and remove any contaminating particles. The chamber will be filled with 10 tons of liquid xenon, and over 500 photomultipliers - vacuum tubes, which are ultrasensitive light detectors and will monitor the LZ. If anything other than dark matter disrupts the rest of the xenon, the detectors will have to show that this is a false alarm.
Promotional video:
As soon as the installation in the underground mine is ready and the experiment is launched, all that remains is to wait. Physicists will be looking for weakly interacting massive particles, or WIMPs, which are the hypothetical building blocks of dark matter. It is believed that most of the time WIMPs pass through ordinary matter without any trace, but they can occasionally collide with ordinary particles.
The LUX-ZEPLIN project participants have assembled a miniature copy of the future installation. Before conducting a global experiment, you need to test it on a smaller and more expensive model.
LZ will remain on for at least five years, but everyone hopes that it will be able to detect WIMPs for the first time, or otherwise exclude them as an ethereal substance that makes up dark matter. Other experiments at Wisconsin's IceCube Center for Particle Astrophysics, as well as projects in Italy and China, are conducting their own experiments to find direct evidence for the existence of dark matter. UW-Madison physicists are also using the Large Hadron Collider in an attempt to detect dark matter, which is created when high-energy particles collide. The race for the discoverers of dark matter is in full swing!
If we can find and measure this substance, we will achieve a greater understanding of how the universe works than ever before. It is possible that dark matter makes up more than 25 percent of the entire cosmos, and once we discover the specific properties of the material, it can reveal secrets that have long remained hidden from us.