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Working in the anti-matter factory

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What happened at the beginning of the universe? What is the universe made of? Is the universe expanding?

What happened at the beginning of the universe? What is the universe made of? Is the universe expanding?

These are some of the big questions researchers at the European Organization for Nuclear Research (CERN) are working to answer. The overarching goal is as ambitious as it is simple—to understand the fundamental structure of the universe.

CERN, located in Geneva, Switzerland, is the largest particle physics laboratory in the world. Over 10,000 scientists work at CERN and worldwide collaborating institutions on topics such as anti-matter, dark matter and sub-atomic particles. One of these research scientists is KAUST alumnus Muhammed Sameed, who completed his master’s degree in material science and engineering in 2012. Sameed works on the ALPHA (anti-hydrogen laser physics apparatus) experiment using lasers to measure the properties of anti-hydrogen.

Cross-sectional depiction of the four Large Hadron Collider detectors: ALICE, ATLAS, CMS and LHCb. © 2014-2018 CERN

At CERN, researchers use a number of instruments to make anti-matter in a state that can be studied. “Make” is the operative word, as anti-matter is not readily found in the observable universe. The absence of anti-matter in our universe, however, does not fit with the theoretical and experimental research to date.

Dirac’s unexpected solution

To understand this, one must travel back to 1928, when a British physicist named Paul Dirac set out to merge quantum mechanics with Einstein’s theory of special relativity. Dirac solved the equation, which very accurately described how electrons behave in our universe, but found that it yielded two possible solutions—one for an electron with a positive energy and one with a negative energy.

Up until that point, physics dictated that a negative energy solution would be impossible, and Dirac ignored it. A few years later, however, he came back to the equation and conjectured that it might be possible for something to have opposite properties to the electron—hypothesizing that the anti-electron may exist.

“It was a matter of luck or a matter of genius,” Sameed explained, that Carl Anderson, another scientist, discovered the anti-electron particle just a year later in one of his experiments, paving the way for an experimental and theoretical basis for the existence of anti-matter.

Dirac and Anderson did not predict how much anti-matter existed at the time of the big bang, but current research shows that every process that creates matter also creates anti-matter in the same amount. Therefore, one would expect that just after the big bang, there would be equal amounts of matter and anti-matter, but this is not the case.

“Is there something weird about anti-matter that changes it into something else, does it decay or is it in some far corner of the universe?” Sameed wondered.

Another complication is the fact that matter and anti-matter annihilate each other when they come into contact, as Einstein’s elegant theory of special relativity, E=mc², predicts: if matter and anti-matter were created at the time of the big bang, then whenever they came into contact, they would annihilate each other and create energy, which would then create mass again—and the cycle would continue.

“If this is true, then the universe as we know it shouldn’t exist; there shouldn’t be this excess of matter that we see in our universe,” Sameed noted.

Trapping anti-hydrogen

In order to shed light on fundamental questions like this, the ALPHA experiment is starting at the basics to understand the basic properties of anti-hydrogen. The research has started with anti-hydrogen because it is the simplest form of anti-matter composed of just one anti-electron and one anti-proton resulting in a neutral charge.

Sameed doesn’t believe we’ll see experiments with other anti-matter elements anytime soon.

“To make the next anti-matter element, anti-helium, you need anti-neutrons, which are notoriously hard to produce and capture. I don’t see this happening in the next decade because there is some much work to be done on anti-hydrogen,” Sameed said.

Muhammed Sameed (M.S. ’12) currently works at CERN in Switzerland and recently co-authored a paper published in Nature focusing on antimatter. Photo by Mark Andrew Johnson.

 

In the past few years, the ALPHA experiment has enjoyed lots of success. In 2010/2011, anti-hydrogen atoms were trapped for the first time.

“At the time we were only able to trap, for example, one anti-hydrogen atom every 15 minutes. This meant that one measurement took weeks because of the need to repeat the measurement for accuracy, but we were also working on improving trapping techniques. In 2016, it was a stroke of luck and a stroke of genius that meant that we improved our technique so much that trapping 20 atoms every four minutes became possible—what took months now took only a few days,” he explained.

The team engineered a new technique for creating cold anti-hydrogen, which meant that the atoms were less energetic due to the lower temperature, and as such, easier to trap and study. This gave researchers the opportunity to do the most precise measurements of anti-hydrogen to date and measure it in a ground state and an excited state, publishing their results in Nature along the way.

Will it rise up or fall down?

After this streak of success, the ALPHA experiment is turning to uncharted territory: anti-hydrogen interacting with gravity.

“Anti-matter hasn’t been studied in terms of gravity because you need a neutral atom. Now that we can work with neutral anti-hydrogen, this opens up the possibility to study the gravity effect,” said Sameed.

Sameed and his colleagues are building a new instrument, ALPHA-g, in order to do this. ALPHA-g is a vertical trap that will give researchers the chance to do a controlled release of anti-hydrogen and observe how the atom behaves.

“We have no theories about anti-matter gravity. Naively speaking, since all matter falls in Earth’s gravity, one can assume that anti-matter also falls, but the problem is that there is no theory to predict it. We might get lucky, in my opinion, if it rises up. That would be a breakthrough. Some theorists say that if anti-matter is gravitationally repulsive, then that could explain how all anti-matter may have accumulated in some far corner of the universe because it is being gravitationally repelled, and as a result, we can no longer see it in our observable universe,” Sameed explained.

Sameed’s engineering expertise means that he and his supervisor from the University of Manchester are responsible for the full design and implementation of the gravity experiment—from the hardware and software to the analysis and deployment.

At the end of 2018, the world’s largest particle accelerator, the Large Hadron Collider, will take a break from smashing particles to undergo maintenance as part of a two-year scheduled shutdown. As a result, the team is working hard to get the ALPHA-g instrument ready for an initial measurement at the end of the summer or beginning of fall ahead of the shutdown.

Anti-matter doesn’t sleep

Due to the sensitive nature of anti-matter, Sameed explained that the ALPHA team has a unique work schedule. Each week, one senior person from the 50 to 60-member team is named “run coordinator,” making this person responsible for every aspect of the experiment. This means that every team member regularly gets a chance to stay in touch with the details of the experiment while building a deep sense of teamwork and responsibility.

The Globe of Science and Innovation at CERN. © 2016-2018 CERN

“The sensitive machines and experiments need to be run 24 hours a day, 365 days a year, so someone always has to be on call, especially if there is a safety consideration,” Sameed added.

In the week that Sameed spoke to KAUST News, he was currently acting as run coordinator.

“Things have completely changed from Monday to now [Wednesday] because, for example, we built a component, there’s another piece of equipment that isn’t working anymore, there’s some software that needs updating, collected data needs analysis. Things are changing on a daily basis. It’s very intense and the hours are long, but it’s exciting because we are working at the cutting edge of science, engineering and computing,” Sameed said.

Future researchers

The cutting edge of science is not only reserved for tenured professors and experienced researchers. CERN needs researchers—including students—from all backgrounds and experience levels to help understand the universe.

“CERN needs a lot of good talent in engineering, computing and math. That’s what KAUST students are good at. It would be interesting to have students and postdocs come visit or do internships. It would be great for KAUST to become a collaborator. Most senior people were first introduced to CERN through the CERN Summer Program. It’s a good funnel and recruitment tool. CERN wants to expose students and universities to the working culture. Simply being exposed shows people that they can contribute,” Sameed said.

“A lot of us underestimate our own abilities. We should let the people at CERN decide whether we are good enough. They have a very nuanced understanding of whether we are the right fit. We may not think we are good physicists, but we might have expertise in a specific area CERN needs helps with. It’s important not to underestimate your abilities,” he added.

 

Source: KAUST

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