September 01, 2009
Cosmic rays bring us information about physical processes that accelerate particles to relativistic energies, the effects of those particles in driving dynamical processes in our Galaxy, and the distribution of matter and fields in interstellar space. Balloon-borne and space based instruments configured with particle detectors have been flown to study cosmic-ray origin, acceleration and propagation. They were also used to search for exotic sources, such as dark matter and antimatter, and to explore a possible limit to particle acceleration in supernova. I will review recent results from cosmic-ray experiments, including the unexpected excess in electrons (and positrons) reported by the Advanced Thin Ionization Calorimeter (ATIC) and Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), along with their implications. The observed excess of leptons is attributed either to a relatively nearby, unidentified astrophysical object that accelerates electrons to those energies or to annihilation of dark matter. I will also discuss some highlights of results from our on-going Cosmic Ray Energetics And Mass (CREAM) experiment that constrain the conventional cosmic ray propagation model.
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Colloquia are held Tuesdays in Room 1410 at 4:00 pm (preceded by light refreshments at 3:30). If you have additional questions, please call 301-405-5946.