Euclid as a dark matter particle collider experiment

This project will test the hypothesis that dark matter particles interact with each other, through forces besides gravity. The hypothesis predicts that dark matter's trajectory through collisions will deviate from the purely gravitational trajectories followed by stars. To test it, we will observe astrophysical versions of dark matter colliders, both during a collision and in their long-term steady state.
The masses and interaction strengths of Standard Model particles are measured by smashing them together in terrestrial experiments like the Large Hadron Collider. Dark matter cannot be accelerated around Geneva, but it is injected into natural colliders such as the Bullet Cluster. We propose to map the trajectory of dark matter debris from more than an order of magnitude more collisions than previously studied. Our measurements will be interpreted against the latest generation of hydrodynamical simulations, with full hydrodynamical effects and dark matter physics beyond the Standard Model.
The proposed test will either confirm a model of 'self-interacting dark matter' (SIDM) on which other measurements are tentatively converging, or rule out dark matter particle interactions as meaningfully influencing the formation of structure in the Universe.