The MAJORANA DEMONSTRATOR experiment is a low-background experiment that is located 4,850 feet underground at the Sanford Lab. USD has long been a member of the MAJORANA collaboration, and current USD efforts are led by Wenqin Xu, Ph.D., associate professor in the Department of Physics.

The goal of the experiment is to understand the particle-antiparticle nature of neutrinos, an abundant but mysterious elementary particle, by searching for a decay process called neutrinoless double-beta decay.

“The MAJORANA DEMONSTRATOR experiment has achieved excellent energy performance and some of the lowest backgrounds in the field, which make it highly competitive in a broad range of physics,” said Xu. “We are glad to have contributed to these achievements and to bring some of the promising physics potential into fruition.”

One such physics project concerns possible axions from the Sun, a dark matter candidate that has its origin theory deeply related to the nuclear force. Xu and MAJORANA colleagues looked for complex temporal-energy patterns that can be imprinted by solar axions in the data collected by the MAJORANA DEMONSTRATOR experiment over a 3-year period. Not finding convincing evidence of solar axions, limits are placed on the parameter that governs the production and detection probability of the hypothetical particle. MAJORANA published this result on the cover of a recent issue of Physical Review Letters, one of the most prestigious journals in physics, with Xu as a corresponding author.

Looking at a different direction, Tupendra Oli, a graduate student from Xu’s research group, found interesting physics at high energy in MAJORANA’s supplemental calibration data. Oli searched for gamma-ray signatures of a known process called (alpha, neutron) reactions and found them in calibration data at the expected energy and with a rate consistent with theory predictions. This MAJORANA result was published on Physical Review C (volume 105, page 064610) with Oli being the corresponding author. Oli successfully defended his Ph.D. dissertation and continues his academic career as a postdoctoral researcher at Argonne National Laboratory.

“These physics results come from collective efforts by the MAJORANA DEMONSTRATOR experiment, which was led by the Department of Energy’s Oak Ridge National Laboratory. Scientific collaboration and training of scientists are at the heart of what we do,” Xu says. “Here at USD, we are extremely grateful for the support my group members have received over multiple years from the U.S. National Science Foundation, the Department of Energy, the South Dakota Board of Regents, as well as the College of Arts and Sciences. Thanks to diverse support, research groups in the Department of Physics actively contribute to the cutting-edge of global research endeavors that explore the nature at the most fundamental level.”
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