Journal cover for Physics Reports

ISSN: 0370-1573

Physics Reports

New 'eyes' to detect the invisible

October 2016

Directional detectors could help to elucidate the mysterious way in which dark matter moves

What is the universe really made of? It's a simple question, but one that continues to mystify physicists. They believe that at least 80% of all the matter in the universe is made up of a substance called dark matter, that has escaped experimental detection up to now.

When astrophysicists only take visible matter into account in their models, their equations simply don't add up. For example, the stars in many distant galaxies rotate around the galactic centres at much higher speeds than can be explained by the visible matter in these galaxies alone.

Now, a new review published in Physics Reports has shown one of the most promising methods to find dark matter: directional detectors.

Professor Anne Green from the University of Nottingham, UK, and colleagues argue that directional detectors could be the way to find dark matter. "We show that directional dark matter detectors, which are sensitive to the directions of the dark matter particles, could detect and also study the properties and distribution of dark matter," says Green.

Theorists say that dark matter must comprise slow-moving neutral particles that are not contained in the best model we have for describing matter in the universe, referred to as the Standard Model of Particle Physics.

One of the most promising candidates for what could make up dark matter are called Weakly Interacting Massive Particles, also​ known as WIMPs. But WIMPs have never been detected. "There have been a few claimed detections but nothing convincing," says Green. "They are predicted to exist in particle theory models. They would have been produced in the Big Bang in the right amount to account for the exotic dark matter," she adds.

Lab-based direct detection experiments aim to detect WIMPs in the Milky Way galaxy, by their rare collisions with nuclei in dedicated detectors on Earth. The sensitivity of direct-detection​ experiments has increased rapidly over the past two decades. Today, they can measure not only energy changes but also which direction the nuclei fly after they have smashed into each other.

This makes directional detectors a powerful tool, not just for detecting WIMPs, but also for studying their properties once detected. "Directional detection has the best future potential for detecting, and hopefully in the longer term studying, one of the best-motivated dark matter candidates," Green concludes.

Article details:

Elsevier has made the following article freely available until the end of the year (2016).

Frédéric Mayet et al.: “A review of the discovery reach of directional dark matter detection,” Physics Reports (2016).