Dark matter remains one of the most elusive phenomena in science today. They are trying to discover it all over the world through many scientific experiments. DarkSide-50 has turned out to be one of the most successful in recent years.
Deep under a mountain in the Italian Apennines, a sophisticated instrument scans the universe for dark matter. Physics students at the University of Massachusetts have been instrumental in the recent discoveries of the DarkSide -50 experiment and, moreover, have been part of this project since its inception.
The DarkSide -50 device and experiments are supported by the National Institute of Nuclear Physics and the Italian National Science Foundation, as well as collaborating institutions from Brazil, China, France, Poland, Spain and Russia.
Physics professor Andrea Pocar and his students designed and built the network, which is one of the key components of DarkSide -50, created in 2009 by an international coalition and housed at the Gran Sasso National Laboratory in Italy. Graduates Arthur Curley and Kristen Randle designed, assembled and installed this delicate device.
Despite the fact that the presence of dark matter can be concluded based on its gravitational effect, physicists are very difficult to identify it due to the almost complete absence of its interaction with "ordinary" matter. As a result, they have to come up with new ways to register it.
DarkSide -50 uses a liquid argon tank with a small pocket of argon gas at the top as a target to attract the particles that make up dark matter. Liquid argon is the target for dark matter particles, and the gas pocket, in turn, amplifies the received signal. The argon core is surrounded by a large volume of pure scintillation fluid, which protects it from radioactive noise that can mimic dark matter signals. The flash of light produced by a particle colliding with the nucleus of an argon atom will indicate that scientists are on the right track.
The process of detecting dark matter means that a scientist needs to become an absolute expert in everything that is not. Graduate student Alyssa Monte looks for events at the edges of the detector, where it is most difficult to collect light and where charge can be captured, or events lose energy with an edge effect. Her work with these less “ideal” regions helps researchers understand the behavior of the entire detector.
Waiting for dark matter to manifest is literally a Zen-like process.
“If we want to see new matter, it will be a completely new signal,” explains Pocar. - Everything is radioactive. So you need to know what all these signals look like in your detector and how they can mimic dark matter. If one of the events eventually gets through, then statistically it will be of incredible importance. We will have to start claiming that this is indeed the signal."
At the DarkMatter 2018 Symposium at the University of California, Los Angeles, Monte and the rest of Pocar's team presented the first talk on the instrument's high sensitivity for a specific class of dark matter principles. The team collected measurement data that they did not even expect to receive.
“It turned out that we are much more sensitive to any other experiment currently operating in the range of a certain mass,” says Pocar. “For decades, research has pushed the boundaries by looking for tough material, but never got it.People began to ask themselves, maybe they should look elsewhere. And so we developed this experiment, and after us other similar experiments began to appear."
The team now have a "fine understanding" of how their sensor records background events.
“Nobody even expected us to say something about low mass dark matter, and we achieved the highest sensitivity in the world,” says Pocar. “Suddenly, we have become a significant player in this game.”