The search for dark matter has stumped scientists since the 1600s, when astronomers began to speculate the existence of something that did not absorb, reflect or emit light but still influenced gravity. Centuries later, little is known about the most abundant matter in the universe.
That mystery is what drew University of Oregon physicist Tien-Tien Yu to theoretical physics. Now, she’s leading a new approach in the search for dark matter.
On Jan. 22, Yu will talk about that research in a Quack Chats pub talk, “Searching for Dark Matter, Uncovering the Mysteries of the Universe.“ The talk begins at 6 p.m. at the Ax Billy Grill at the Downtown Athletic Club, 999 Willamette St., in Eugene.
“I will present the evidence for the existence of dark matter, describe a few of the methods to search for dark matter, and discuss a particularly promising direction in research,” Yu said.
For the last several decades, the popular thinking in the physics community is that dark matter is weakly interacting massive particles, known among physicists as WIMPs. The Xenon dark matter research project at the Gran Sasso National Laboratory deep beneath Italy uses 15 to 165 kilograms — with an ultimate goal of reaching 10 metric tons — of liquid xenon to capture WIMP interactions. Those efforts have been unsuccessful.
“Experimentally, we have well-developed ways to search for WIMP dark matter,” Yu said. “However, the null results from experiments like Xenon1T and the experiments at the CERN Large Hadron Collider prompt us to think beyond the WIMP.”
Prior to joining the UO, Yu was a fellow in the theoretical physics group at the CERN particle physics laboratory in Geneva, Switzerland, and a post-doctoral associate at the Yang Institute for Theoretical Physics at Stony Brook University. During her postdoctoral studies, Yu started to question the theory and decided to take a different approach and look for different kinds of dark matter.
“The traditional methods used for dark matter searches are optimized for WIMPs but are not sensitive to most other kinds of dark matter,” Yu said. “What my collaborators and I found was that with small modifications to existing technologies, we could expand the potential of experiments to look for other, non-WIMP dark matter candidates.”
She co-founded the Sub-Electron Noise Skipper-CCD Experimental Instrument collaboration, an experiment using silicon chips, much like those found in digital cameras, to search for dark matter passing through the Earth. It goes by the acronym SENSEI.
“The idea is to look for dark matter interacting with the electrons in the silicon atoms,” Yu said. “Although this was not a particularly new or novel idea, no one had actually built a dedicated experiment to look for these interactions, nor recognized the great potential for such an experiment. As a consequence, SENSEI has been able to set world-leading constraints despite its diminutive size.”
A preliminary run using a prototype consisting of less than 0.1 gram collected data at Fermilab in Chicago. Detection methods must be deep underground to shield them from cosmic rays and other radiation. Sensors are currently being placed in Canada, around two kilometers underground.
During her Quack Chat, Yu will talk about the new approach and why, while they still have not detected dark matter, early results are promising.
“Our ultimate goal is to uncover the nature of particle dark matter,” Yu said. “The next few years will be very exciting due to the variety of new experiments coming online that, like SENSEI, are looking beyond the WIMP.”
—By Molly Blancett, University Communications