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March 4 Colloquium

Timothy Cohen, SLAC

What Light Can Teach Us About Dark Matter

Consistency between big bang cosmology and precision data requires that about 80% of the matter in our Universe consists of a new particle — the dark matter.  Uncovering the identity of this state is one of the driving motivations for exploring theories beyond the Standard Model of particle physics.  One compelling hypothesis is that the dark matter is a massive particle whose only interactions occur via gravity and the weak force.  This so-called WIMP paradigm leads to a wide variety of experimental signatures.  In this colloquium, I will argue that one compelling way to explore WIMP models is by analyzing measurements of cosmic ray photons.  I will provide a pair of case studies to demonstrate the kind of physics that can be extracted from gamma-ray data.  The first is an analysis of the Fermi line at 130 GeV, with an emphasis on the implications for WIMP models; the second demonstrates that data from H.E.S.S. can be used to constrain compelling models for multi-TeV WIMPs.  These examples will illuminate how much there is to learn about the nature of dark matter by studying light.

REFRESHMENTS:  3:40 p.m. in the Willamette Atrium COLLOQUIUM:   4:00 p.m. in Willamette 100