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The Search for Dark Matter

Danielle Speller
Danielle Speller in her lab. [Photo: Will Kirk]

Most of us know that our universe is made of matter, and that matter has mass. But scientists still don’t understand everything about mass. Especially why some particles have smaller mass than others, or why some of their behavior doesn’t follow the standard rules. More than 80 percent of the mass in our universe is “dark matter” that’s invisible to us. Danielle Speller, assistant professor of physics, is working to better understand these mysteries about the nature of matter and mass.  

Speller’s work focuses on low-energy searches for new physics. She’s hunting for new particles that could be the constituents of dark matter and for rare types of radioactive decay. She’s looking for a class of dark matter candidates known as axions in hopes of studying how they behave. She’s also looking for a rare nuclear process called neutrinoless double-beta decay. Each step she takes toward detecting evidence of either of these could reveal new things about how we understand physics. 

You start trying to tie together the smallest things in the universe, and the patterns of behavior that they exhibit, with consequences you see at the most far-reaching parts of space.”

— Danielle Speller

Collaborating with Top Experiments

Speller works on these problems with two top experimental nuclear and particle physics projects. The Haloscope at Yale Sensitive to Axion Cold Dark Matter (HAYSTAC) is a cutting-edge experiment looking for axions. The Cryogenic Underground Observatory for Rare Events (CUORE) in Assergi, Italy, is one of the leading searches for neutrinoless double-beta decay.  

These facilities don’t smash particles together like the widely known Large Hadron Collider at CERN. They’re quiet, shielded experiments built around cryogenic detectors that scientists use to observe key signals. At HAYSTAC, they’re looking for evidence of axions via light, or photons. Photons are produced when dark matter is converted by interacting with a large magnetic field. With CUORE, researchers gather heat signals that might prove neutrinos are their own antiparticles.  

Parts of the planning, testing, maintenance, and data analysis for the larger facilities will happen at Homewood as Speller establishes her new laboratory, even though the collaborative facilities are distant. Continual partnership with other scientists on both project teams is key. Speller’s four-person lab contributes to remote monitoring of the CUORE detector and to data analysis of the signals the project gathers.

Dark Matter at Homewood

Her recently built lab includes a dilution refrigerator, a cryogenic device that will allow her to create experiments to search for new physics. It will also help her team develop and test sensors and other apparatus for future versions of CUORE and HAYSTAC. She also hopes to build a haloscope that could make its own searches or work in conjunction with other experiments to expand search capabilities for new signals. 

“This is an exciting field to work in because we can both develop things locally while remaining plugged into the field at large,” she says. Her goal is to build a lab that can take advantage of accessible, room-size, tabletop experiments. Those experiments can lead to a better understanding of new components of physics, providing a complementary approach to large underground facilities. Discoveries await, she says. In time, the search for new physics may be pushed forward by novel tests right in the basement of the Bloomberg building.