Dr. David Wittman

University of California, Davis

Large Dark-Matter Colliders

102 Cardwell Hall

September 23, 2013

4:30 p.m.

The non-gravitational properties of dark matter remain elusive after many years of searches by underground direct-detection experiments, colliders, and by telescopes looking for annihilation signatures in the sky. I will introduce an up-and-coming method which uses galaxy clusters as dark-matter colliders to measure the dark matter self-interaction cross-section which, remarkably, could be as large as a typical strong-force cross-section and still escape detection so far. Only astrophysical observations can probe this aspect of dark matter, and there are a variety of tantalizing observations which would be explained by self-interacting dark matter (SIDM) just below the current upper limits. Within the next several years, the colliding-cluster method will be improved to the point where SIDM will either be detected or ruled out as an explanation for the other astrophysical observations.