The search for dark matter

Dr. Gilles Gerbier, holding a silver sphere, and Dr. Alvine Kamaha, with his arms crossed, smile at the camera.

Photograph by Bernard Clark

With the world’s attention on Queen’s physicist Dr. Art McDonald after he received the Nobel Prize in Physics for breakthrough neutrino research, we decided to shine a spotlight on other innovative Queen’s physicists. Read more – and find links to all our physics research profiles – in The Biggest, Deepest Questions.

At Sudbury's SNOLAB, Gilles Gerbier, Queen's Professor and Canada Excellence Research Chair, is studying the nature of the elusive dark matter particle while post-doctoral fellow Alvine Kamaha is building new apparatus to use in the underground lab to find the particles.

“I wanted to be part of something big,” says Dr. Kamaha, who studied in Cameroon and Italy before coming to Queen's.

“When I came here for my PhD, I was blown away – knowing that you can find something that has such a big impact. Dark matter is believed to be 80% of the mass of the universe. Even though we don't know right now what the application will be when we find it, you know you have contributed to a better understanding of the universe.”

Alvine Kamaha and Gilles Gerbier

Alvine Kamaha, Post-doctoral fellow
Gilles Gerbier, Professor, Canada Excellence Research Chair
Queen's Department of Physics, Engineering Physics & Astronomy

Gilles Gerbier: The experiments I am working on at SNOLAB are designed to test hypotheses on the nature of dark matter particles. There is a lot of evidence that there is dark matter – not ordinary matter (protons, neutrons, electrons) – particles of a different nature.

The goal of our experiments is to detect these particles. We know the impact they should have on detectors and on matter, and we know the interactions are going to be tiny and very rare.

Dark matter is our little music – it is very tiny music and to listen to it, we have to take off all the noise from all the other particles.

The detectors have to be very good – we’ve been building detectors for 30 years now, and still we haven’t seen any hint of dark matter. We have to build new and better detectors. This is what we are developing in my group – detectors that are sensitive to a mass at the lower end of the mass range (such as the proton). I proposed two experiments focusing on the quality of the instruments to address this low mass. You cannot buy these detectors off the shelf.

Alvine Kamaha: I am working on one of those experiments, called New Experiments With Spheres (NEWS). It’s basically a spherical vessel made of a metallic material (like copper or stainless steel) that contains a tiny ball attached to a rod.

The sphere is filled with gas that has certain properties – when dark matter particles interact in the detector, they could deposit energy and ionize the gas. When the tiny ball is put to high voltage, the electrons liberated in the gas will drift toward the centre. Because of the high electric field at the ball, there will be an avalanche. The drifting of the ions from the avalanche yields an electrical pulse that is recorded. You collect a bunch of these avalanche data. They can sometimes lead you to dark matter and sometimes they can lead you to other things.

At the end of the day, analyzing the collected data, you remove what is not dark matter and you are left with what you think might be dark matter.

Gilles Gerbier: This is a field with a strong hope to find something. Sometimes you misidentify things. Only when several experiments (and there are experiments happening all around the world using different techniques) see the same signal, then there will be some guarantee that there is something (dark matter).

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