Fresh eyes for dark matter

Astronomical observations indicate that dark matter is an important component of the universe. It's estimated to be about five times as common as visible matter. In order to prove its existence, researchers are using extremely sensitive detectors to search for interaction between dark matter particles and normal particles. The international collaboration XENON, which includes a team headed by astrophysicist Professor Marc Schumann of the University of Freiburg, has presented the first measurements made by the new detector, XENON1T. After just 30 days of taking measurements, XENON1T has shown itself to be the world's most sensitive detector for dark matter. However, it has not found indications of dark matter particles in this short time.

The earth's natural radioactivity and cosmic radiation present a major challenge when it comes to finding dark matter particles. They produce interference, comparable with the light pollution caused by cities, which prevents astronomers from seeing the night sky clearly. The data produced in the first 30 days of measurements show that the detector has beaten the previous record for the least radioactivity. With XENON1T, the interference is many orders of magnitude lower than in the normal terrestrial environment. "Due to the combination of the size of the detector and the purity of the data, XENON1T has a very good chance of finding dark matter particles in the coming years," says Schumann.

Since late 2016, XENON1T has been in operation in the underground laboratories at Gran Sasso, Italy. XENON1T uses around 3200 kilograms of liquid xenon as detecting material, making it the biggest such detector ever built. All that can be seen of it in the subterranean laboratory is a gigantic steel water tank and a three-storey, transparent structure. The tank is filled with purified water, which protects the detector in the middle from radiation from the environment and residual cosmic radiation. The actual detector, known as a liquid xenon time projection chamber, is located inside an insulated vessel which ensures that the liquid xenon remains at minus 95 degrees Celsius - yet the water does not freeze.

Researchers from the US, Germany, Italy, Switzerland, Portugal, France, the Netherlands, Israel, Sweden, and the United Arab Emirates are working together in the international XENON collaboration. The German researchers are from the University of Freiburg, the Max Planck Institute for Nuclear Physics in Heidelberg, the University of Mainz, and the University of Münster. The Freiburg team led by Schumann is responsible for the experiment's data collection system and coordinated the design and construction of the time projection chamber.

Original publication:
First Dark Matter Search Results from the XENON1T Experiment, XENON Collaboration, arXiv:1705.06655
https://arxiv.org/pdf/1705.06655.pdf

Further information on XENON1T

Contact:
Professor Marc Schumann
Institute of Physics
University of Freiburg
Phone: 0761/203-96894
E-Mail: marc.schumann@physik.uni-freiburg.de