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The Daily Wildcat

The Daily Wildcat


    Physicists study dark side of supersymmetry


    Courtesy of Elliot Cheu

    Elliot Cheu, the associate dean at the College of Science and professor of physics, stands next to test equipment used for the ATLAS partical physics experiment. Cheu is looking for new theoretical particles to ultimately understand the building blocks of the universe.

    UA researchers are looking for the possible theoretical particles that will fill the gaps of what scientists don’t know in the Standard Model of particle physics, the theory that explains the identities of the subatomic particles that are the building blocks of matter and their interactions.

    Elliott Cheu, the associate dean at the College of Science and professor of physics, studies Supersymmetry, an extension to the Standard Model. This research could potentially allow physicists to understand the origin of mass.

    Cheu and his research team utilize the Large Hadron Collider at the European Organization for Nuclear Research, which is located in Switzerland and the most powerful particle accelerator in the world.

    “We [look] for new types of particles,” Cheu said. “When one tries to understand why the Higgs mass is so small, people postulate that there are these extra particles.”

    Supersymmetry is the study of those theoretical extra particles, which are not present in the Standard Model.

    Cheu said the research interests him because when people catalog the amount of matter in the universe, stars, dust and gas only make up about 4 percent of it.

    “You have to ask, what is the rest of it?” Cheu said. “There are two other possibilities: One is called dark matter and one is called dark energy, and Supersymmetry has the possibility of being the dark matter candidates. About 25 percent of the matter is dark matter, and the idea is that dark matter could be the result of these supersymmetric particles.”

    Matt Leone, a physics graduate student, analyzes large data sets in order to look for vector-like quarks, which are outside the Standard Model and are potential particles of Supersymmetry. He uses a process called machine learning to identify these particles. This is similar to the process that Gmail uses in order to filter out spam by using a large amount of different variables.

    “We simulate a data set by simulating [a] known background and known possible signal which theoretically might exist,” Leone said. “Then, we’ll create an analysis that tries to separate these two to see if you can identify that signal, and we carry that over and apply it on the data that was actually measured by the ATLAS detector.”

    Aside from his research with the particle detector, Cheu also collaborates with the department of astronomy on the Large Synoptic Survey Telescope project.

    “I am one member of a large collaboration of people who are building this telescope, and we’re in charge of a small part of it,” Cheu said. “We are in charge of building the power supplies for the camera.”

    Cheu said the telescope will be sent to Chile and will be able to take images quickly enough that there will be a quasi-movie of the night sky over the course of 10 years.

    The images will then be added together to increase the visibility of objects in the composite image and allow galaxies that are faint in one image to become brighter in the composite, Cheu said. The scientists will then be able to map roughly 10 billion galaxies.

    “The group that I am working with on the LSST, we’re very interested in measuring the other part of the matter called dark energy,” Cheu said. “One of [the] impacts of dark energy is that it seems to be causing the universe to expand more quickly.”

    The two projects are tied together, Cheu said, because they incorporate scientists’ understanding of matter and what the constituents of the universe we live in are.


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