Courtesy of Sameed

Sameed '11 poses with antiproton trap.

April 5, 2021

Sameed ’11 Harnesses Lasers to Uncover Secrets of Antimatter

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Muhammed Sameed ’11 is peeling back the curtains of the subatomic world to learn more about matter’s elusive counterpart — antimatter. 

In a recent paper published in Nature on March 31, Sameed explained how he and his collaborators at the European Organization for Nuclear Research developed a new technique to help physicists pin down this part of the universe that has escaped scientists until now.

Sameed explained that the objects of everyday life — like cars, textbooks and our bodies — are made up of matter. But mathematical equations that govern the behavior of the universe predict the existence of something that doesn’t match everyday matter, what is now known as antimatter. 

According to Sameed, antimatter differs from matter by having the exact opposite value for some physical properties. For example, a particle of antimatter and a particle of matter have the exact same mass, but they would have exact opposite electric charges, Sameed said.

Sameed explained that when a particle of matter and antimatter meet, their opposite properties cancel out, and their mass is converted into energy — which makes antimatter hard to come by. Therefore, antimatter must be studied in a vacuum chamber, an environment in which there are no other particles of matter around.

Even in a vacuum, antimatter is difficult to study, Sameed said. The antimatter — which has energy that makes it move — has to be slowed down to the point that it won’t touch the matter-filled walls of the chamber.

Sameed and his collaborators have developed a mechanism to do just that — laser cooling. Sameed specifically studies the properties of antihydrogen, the most basic form of antimatter.

In order to develop the method of laser cooling, Sameed said he and his team first had to study the energy levels of antihydrogen. When a laser is shined on an atom of antimatter, that atom absorbs the light and transitions from a lower to higher energy level, Sameed explained. 

Upon absorbing light energy, a moving atom will receive a “small kick” that pumps the brakes on the atom’s motion, according to Sameed. 

“With laser cooling we can essentially slow down … antihydrogen atoms to such a slow speed that they’re essentially … trapped for many, many hours, which now gives us enough time and ability to do experiments,” Sameed said. 

In one such experiment, Sameed hopes to study how antimatter behaves under the influence of Earth’s gravity — essentially, whether antimatter falls down, stays in place or floats up.

Since there are currently no theories to predict this behavior of antimatter, Sameed said the results of the experiment may prove to be controversial in the scientific community.

“Most of us are very pessimistic about this, we expect that [antimatter] falls down the same way as regular matter does,” Sameed said. “There’s a handful of scientists out there that are saying that no, antimatter will go up.” 

Although antimatter might seem far removed from what people encounter in their daily lives, it has some real-world applications. 

According to Sameed, Positron Emission Tomography — a technique used by physicians to measure the activity of body tissues — harnesses the power of antimatter particles called positrons, also known as antielectrons. 

By studying the properties of antihydrogen, Sameed hopes to further unlock applications of antimatter that currently don’t exist. 

But for researchers like Sameed, the motivation to uncover the secrets of antimatter comes down to a passion for science.

“For me and my team, most of us are doing this for the sake of science, for the curiosity to further develop our understanding of how nature behaves,” Sameed said.

Although antimatter is Sameed’s bread and butter, researching some of the most elusive particles in the universe comes with its own set of challenges. To actually create the antihydrogen atoms being studied, researchers at CERN have to monitor a beam of antiprotons for a 24-hour timeframe, necessitating work shifts that bleed into odd hours of the night, Sameed said.

But it is all worth it for Sameed.

“Being able to work in one of the most cutting-edge research institutions has been … a dream, to be coming here and then to actually get publications in some of the best journals in academia,” Sameed said.

Sameed also said he felt fortunate to learn how to blend science and entrepreneurship by commercializing the products of his scientific efforts. 

When the pandemic hit, Sameed recalled that he and his team at CERN responded to the global deficit of ventilators by designing a ventilator prototype and making the design available to manufacturers around the world.

“This was another like major success, where you could basically get scientists to come together and not necessarily just do fundamental science, but really quickly use their diverse expertise to build something for the betterment of humanity,” Sameed said.

Sameed’s love for fundamental physics took root at Cornell, where his summer research with Prof. Ivan Bazarov, physics, at the Cornell High Energy Synchrotron Source launched him toward a career in particle physics.

“Basically I was digging a hole for myself in this field,” Sameed said. “It started getting more and more exciting, so I just stuck with it.”