Why does dark matter matter?

“The problem, of course, is dark matter.”

Those are the blunt words of University of Adelaide’s Dr Irene Polonino, a postdoctoral research fellow at ARC’s Center of Excellence in Dark Particle Physics, based at the University of Adelaide.

It tries to understand how the world around us is made by capturing the vibrations of dark matter.

Dark matter might confuse you, but it’s important. In addition to keeping developing important detection technologies, it could find applications that we haven’t considered yet.

Most of all, it is important because of its potential paradigm-shifting significance in our understanding of the universe.

The primary candidate for dark matter is a new type of elementary particle that has yet to be discovered.

Polonino is part of an ambitious project that spans the width of the Earth: Sabir (Sodium iodide with active background rejection experiment). Half of the SABER experiment is centered in Australia, making it one of the most sensitive, expensive, and detailed scientific endeavors ever undertaken in the country.

Polonino believes it has world-shaping potential.

“The project, in my opinion, is a very challenging and cutting-edge experiment, and it is here in Australia. It can change history and study dark matter.”

Erin Bologna
Irene Polonino. Credit: Supplied

The highly sensitive experimental device is a sophisticated device. Polonino says the research and development around building the sensors could be used in other areas. “The techniques we apply to detect dark matter and keep the background as low as possible are very important. All of the technologies we develop can be reused in different fields.”

Physics is often notorious for being somewhat intangible. But advances in our understanding of the universe often have direct—and sometimes unintended—effects on society.

These effects could be in the form of new technologies. Advancements in physics can change our perception of the world around us. So, why should we care about dark matter? Polonino believes that understanding the universe is an essential part of how we interact with it to improve ourselves.

“Dark matter is not reported in what we call the Standard Model. The Standard Model of particle physics is our bible. It announces everything we know about all particles, all matter, everything,” she explains.

The Standard Model of particle physics needs to change because there is experimental evidence for dark matter. And we will understand more deeply all particle physics and all their interactions. It would be a huge improvement in terms of particle physics, and all related disciplines.

“Knowledge about particle interactions has proven very important, for example, in the medical field and has really helped in drug development, and some cancer treatments, for example.”

It doesn’t matter

“Dark matter is the majority of matter in the universe,” Polonino says.

“If we understand what it’s made of, we’ll take an important step toward understanding our universe and our surroundings. Dark matter isn’t something that has nothing to do with Earth. Millions of dark matter particles pass through Earth every second. It’s not something we want to study far away, in another galaxy, for pure knowledge.

“Discovering what most things around us are made of, will require changing the Standard Model of the elementary particles known to date. Beyond the scientific perspective, changing the Standard Model will have impressive media interest: the scale can be represented by the importance given by the media to the confirmation of the Higgs boson, in 2012 (He won the Nobel Prize in 2013), which has already been predicted by the Standard Model.”

The SABER South experiment will also have a significant impact on physics research in Australia, according to Polonino. We will have high visibility. Australian research will benefit. I think dark matter is one of the most important problems. Australia is playing a leading role.”

More than 20 years ago, an experiment deep in an Italian mountain claimed to have resulted in the first direct detection of dark matter.

But the results have never been confirmed.

“The SABER project is, in my opinion, a very challenging and evolving experiment, and it’s here in Australia. It can change history and study dark matter.”

Erin Polonano

The whole difficulty with this elusive matter – which should make up 85% of all matter in the universe – is that it’s so difficult to detect, because it interacts so weakly with ordinary matter.

Cosmological observations have proven this for decades ought to Be there and an international team of physicists is now trying to settle scores with dark matter.

The principle behind the experiment is “very simple,” Polonino says.

The earth revolves around the sun. So far, so good.

But the Sun is also moving through the Milky Way, and all of the dark matter in our galaxy. Polonino offers an analogy: “The effect is that you have wind – you can compare it to riding a bicycle. If you’re riding a bike, you have a wind effect on your face, but the air is not actually moving. The effect is there because you’re moving through the air otherwise you wouldn’t notice it.” The principle is the same. .”

Due to its nearly circular orbit around the Sun, for six months of the year, the Earth moves in the same direction as the Sun through the galaxy. For the other six months, we move in the opposite direction.

As a result, any detection of dark matter should show a modification — a wave pattern. The peak is around June 2, and the trough is around December 2.

The DAMA/LIBRA experience in Italy during the early 2000s showed exactly this.

Case closed? not exactly…

Polonino explains that the DAMA/LIBRA results contrast with other, more sensitive experiments that aim to find dark matter through various means. The mod found by DAMA/LIBRA could be from a different source.

“It could be what we call the ‘seasonal effect’ – cosmic muon rays come mainly from space,” Polonino explains. Muons depend on humidity and temperature, so their flux is greatest in the summer and decreases in the winter. We know that the seasonal dependence of muons appears with a maximum around June 2. Therefore, we need to experiment in the other hemisphere.

“If what DAMA detects is due to muons, we would expect to detect the same modification but with the opposite phase.”

By having two detectors, one in each hemisphere, SABER aims to confirm or deny DAMA’s claim that it has seen dark matter. One of the reagents will be in the same DAMA lab in the north.

Stawell Underground Physics Laboratory launched. Credit: University of Melbourne.

The other, SABER South, is much closer to home — in Stawell’s underground physics lab. The laboratory is located in a working gold mine 1km below the Victorian rural town of Stawell, about 235km northwest of Melbourne.

“SABER has a lot of potential,” adds Polonino. “It is the only dark matter experiment located in the Southern Hemisphere because Stawell is the first underground physics laboratory in the Southern Hemisphere.”

The detector would have to be underground to suppress background radiation that would crowd out any possible signals of dark matter.

What can SABER South achieve?

SABER South is set to begin detecting muons in early 2023. Dark matter detection will begin in the last quarter of 2023, Polonino says. “In one year, we’ll be ready to start.”

“I think we can make history because the other experiments that are currently being done with sodium iodide crystals are not sensitive enough yet and they are all located in the northern hemisphere. So, our potential is very high,” she says.

So when should we expect to celebrate the results of the trial?

“It is the only dark matter experiment located in the Southern Hemisphere because Stawell is the first underground physics laboratory in the Southern Hemisphere.”

Erin Polonano

“We expect to have the first results at the end of 2025,” says Polonino. “I think the best side. That’s why I love this experience. I chose SABER South. I wanted to work here. I’ve been working at SABER North before and I asked for a position to work at SABER South because, no matter the outcome of SABER South, it’s going to be a success. No There is a possibility of failure.

“If nothing is detected, it appears to have nothing to do with the muons. If we see the modification but with the opposite phase, then we can study the muons. And if we detect the same modification as DAMA, we might have found dark matter.”

Issue 89

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