Invisible “Dark Matter”

A 3D rendering of the detector

A 3D rendering of apparatus that will be used to detect the dark matter (Matthew Hoff, Berkeley Lab)

From the September 2014 edition of Desktop News | Three University of Alabama physicists are among dozens of researchers planning and developing a new international search for dark matter – an invisible material that scientists believe makes up roughly 27 percent of the universe’s mass. Drs. Andreas Piepke, Jerry Busenitz and Ion Stancu, all professors in the Department of Physics and Astronomy, are University representatives on the project, which is being managed by the Lawrence Berkeley National Lab.

UA scientists have collaborated on the project since its 2012 outset and received a boost last month when the U.S. Department of Energy and the National Science Foundation announced it was one of three new dark matter projects selected for support. The research group is composed of 128 researchers from 29 institutions in the United States, the United Kingdom, Portugal and Russia.

Dark matter is known to exist, scientists say, partly because they see the influence of invisible materials in gravity, including both within and around our own Milky Way galaxy.

“It’s like a soup in which we’re living,” Piepke said.

The soup analogy is, perhaps, most apparent when thinking of the Earth’s location in space, positioned within one of our galaxy’s rotating spiral arms and influenced by dark matter both within, and well outside, our atmosphere.

In the newly endorsed Lux-Zepelin, or LZ, experiment, the group will use liquefied xenon and a high-tech detector to search for a type of dark matter particle called WIMPS, or weakly interacting massive particles. The apparatus will look for collisions between the nuclei of xenon atoms and WIMPs, evidenced by a transfer of kinetic energy from the dark matter article to the xenon atom.

“That energy deposit is what we’re looking for,” Piepke said. “That is the signature for the detection of dark matter.”

The experiment is tentatively scheduled to begin in 2018. First, scientists and engineers must build the detector, and the UA physicists are already actively filling a critical role in that process.

All material used in the detector’s construction must be tested to ensure it does not exceed the acceptable thresholds of radioactivity and radon as too much would interfere with the project’s particle detection efforts. Highly sensitive, custom-built detectors at The University of Alabama are already testing candidate materials.

The experiment’s selected data centers will also be tasked with recording, processing and storing huge amounts of data from the experiment. Stancu is leading a task force that will establish the criteria the candidate data centers must meet for selection.

The UA researchers will also custom-make sources which emit gamma rays and neutrons to help calibrate the detector prior to the experiment’s data collection phase. This, too, helps the scientists differentiate between atomic collisions in which they are and are not interested.

For more information about the project, visit www.uanews.ua.edu/2014/08/ua-researchers-to-embark-on-new-search-for-mysterious-dark-matter.