Researchers at the underground SNOLAB in Ontario, Canada, operate its DEAP-3600 experiment and have released results from the team’s first year collecting data on dark matter, confirming that the sensitive detector is working as anticipated.

The $30-million project is the largest dark matter detector of its kind in the world, employing a novel technique of using only scintillation light in liquid argon—light generated when a particle interacts with an argon nucleus.

“I am very pleased with the year one results from the DEAP-3600 experiment, which demonstrate a new technique using liquid argon for a dark matter particle search,” says Mark Boulay, a Carleton University physics professor and leader of 80 domestic and international researchers while the Canadian research chair in particle astrophysics and subatomic physics. “This program will extend our sensitivity to dark matter, with the exciting potential of observing this dominant component of our universe for the first time.”

DEAP-3600 researchers—including teams from the University of Alberta, Canadian Nuclear Laboratories, Carleton, Queen’s, Laurentian University, SNOLAB and TRIUMF, along with international partners—have published the analysis of data collected during the first year. While the scientists have not seen any potential dark matter particle interactions, the research project allowed the team to understand the limits on how dark matter particles interact with argon nuclei.

To get the necessary level of sensitivity, the detector needs to be operated deep underground at SNOLAB to filter out background cosmic rays from the atmosphere and strictly control levels of radioactivity, both of which could lead to false signals. With DEAP-3600, Boulay and his team demonstrated some of the lowest levels of radioactivity ever achieved in dark matter searches, and the group expects to further improve sensitivity by continuing to collect data.

“It’s great to see these new results from DEAP submitted for publication,” says Dr. Nigel Smith, executive director of SNOLAB. “After a great deal of work by many people within the collaboration and facility, SNOLAB congratulates the DEAP team. The analysis of a full year’s data shows the quality and stability of the DEAP-3600 detector, and the potential of this technique for searching for dark matter interactions—and helps define the way forward for the potential larger and more sensitive experiments needed to tease out the physics of this elusive material in the future.”

A paper detailing the results of the latest run can be found online, while DEAP-3600 will continue to collect data at SNOLAB until 2020, when its ultimate sensitivity should be reached.

“We are extremely pleased that the work we put into the DEAP-3600 experiment has resulted in this beautiful data we have submitted for publication,” says Dr. Chris Jillings, SNOLAB research scientist and Laurentian University adjunct professor. “Our work is the most sensitive search for cosmological dark matter with liquid argon and is a scientific and technical advance. We are working hard as a collaboration to press forward with analysis of more data and the SNOLAB/Laurentian University scientists will continue to lead key parts of the analysis and detector operation. We thank our Canadian and international funding agencies for their support of our work.”