Unveiling Dark Matter: Oxford Researcher Lizzie Bloomfield on Direct Detection with Darkside 20K

On Oxford Sparks, Emily interviews Lizzie Bloomfield, a first-year PhD student in the University of Oxford's particle physics department, about dark matter. Lizzie explains that dark matter is a form of unseen matter that cannot emit light but exerts gravity, shaping galaxies and clusters. She describes how theorists propose candidates such as WIMPs and how scientists try to detect them directly with a detector built in Italy. The project Darkside 20K uses a 50-ton cryogenic liquid-argon target housed in a large underground tank to minimize background noise. The search is a long-term effort to narrow the particle properties and energy window, with a potential discovery meaning a new particle added to the Standard Model and a major step in fundamental physics.

Background: What is dark matter and why it matters

Lizzie Bloomfield explains that dark matter is essentially a form of hypothetical matter that exists in the universe, and we believe it exists due to gravitational effects on galaxies and clusters. It is non-luminous, meaning it does not interact with light, but it exerts gravity that shapes cosmic structures.

"Dark matter is essentially a form of hypothetical matter that we believe exists in the universe, and it does not interact with light but it interacts with gravity." - Lizzie Bloomfield

The Quest for Direct Detection: How theoretical particles become experimental targets

Bloomfield outlines how theorists propose candidates like weakly interacting massive particles, or WIMPs, which might fill the dark matter content. There are several theoretical candidates, with WIMPs being among the most popular, and experiments aim to detect their interactions with ordinary matter.

"There are several theoretical candidates, with WIMPs being among the most popular, and this experiment aims to detect their interactions with the detector." - Lizzie Bloomfield

Detector Design and the Darkside 20K Project

In Oxford, researchers build components for a detector that will search for dark matter in a large underground lab in Europe. The detector is a dual phase time projection chamber housed in a 30 by 30 meter tank in Italy with about 50 tons of liquid argon kept at cryogenic temperatures. The search is a long-term effort to reduce background noise from cosmic rays and the environment by placing the detector underground.

"The detector in Italy is a 30 by 30 m tank with 50 tons of liquid argon kept at cryogenic temperatures." - Lizzie Bloomfield

Timeline, Challenges, and Potential Impact

The talk covers how long these experiments take to move from concept to potential discovery, with Darkside 20K aiming for commission and first runs by 2026 or 2027. A discovery would imply adding a new particle to the Standard Model, a landmark achievement in particle physics.

"If we could possibly add another particle to the standard model, it would be amazing." - Lizzie Bloomfield