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From the Director of Particle Physics & Astrophysics: Cosmology Frontier Beckons

(Photo - David MacFarlane)

Over the last decade or more, it has become clear that particle physics and astrophysics are confronted by a set of mysteries whose resolution will likely revolutionize our view of both the subatomic world and the large-scale universe around us. Most of the matter in the universe is in the form of dark matter, a type very different from the ordinary matter we see around us and not yet seen by experiments on Earth. We also know from precise measurements of the expansion rate of the universe that, rather than slowing down due to gravitational attraction, it is actually speeding up. Some form of dark energy, representing about 75 percent of the energy density of the universe, is apparently responsible for this unexpected observation, but we know nothing more about it. Resolving these mysteries will change our understanding of particle physics and cosmology in profound ways.

Over the last 18 months, great strides have been made in formulating an optimal strategy for addressing these pressing questions. Last fall, the Particle Astrophysics Scientific Assessment Group (PASAG) chaired by Steve Ritz of U.C. Santa Cruz completed its work in providing priorities for particle astrophysics as part of the U.S. High Energy Physics (HEP) program. Their recommendation was to pursue a comprehensive campaign of experiments over the next decade to seek out the nature of dark energy, dark matter, high-energy cosmic rays and the cosmic microwave background as some of the most fundamental questions confronting particle physics today. Just last week, the committee for a Decadal Survey of Astronomy and Astrophysics (ASTRO2010) made public their report for the National Research Council on "New Worlds, New Horizons in Astronomy and Astrophysics," in which next-generation space- and ground-based experiments to pursue dark energy figured prominently as the highest-priority new projects for the coming decade. This convergence of views on the scientific need to address the nature of dark matter and dark energy presents HEP with a clear and compelling path forward.

As a particle physicist, I have found it particularly fascinating to watch the Astronomy and Astrophysics community work its way through the planning process over the last 18 months. The ASTRO2010 report is the 6th in a series of such studies conducted once per decade since 1964. The integrity of the process and the uncompromisingly clear nature of the recommendations, achieved in the face of a wealth of competing exciting science opportunities and significant fiscal constraint, is really a model for many other fields. Roger Blandford, director of the Kavli Institute for Particle Astrophysics and Cosmology here at SLAC and Stanford, did a superb job in leading this process supported by a broad community effort and engagement. Hundreds of white papers on science, technology development, theory, computation and laboratory astrophysics were considered. Five science frontier panels and four program prioritization panels gathered ideas and information, and debated priorities. The end product is a compelling scientific program, with dark energy experiments figuring prominently in the highest priority projects: the Wide Field InfraRed Survey Telescope (WFIRST) in space and the Large Synoptic Survey Telescope (LSST) on the ground.

The Particle Physics and Astrophysics program at SLAC is well positioned to figure prominently in the Department of Energy’s engagement in the PASAG and ASTRO2010 recommended dark energy and dark matter program. For LSST, we are leading the development of the main DOE contribution, the 3.2 gigapixel camera for the telescope, with partnering universities and Brookhaven National Laboratory. We have been partnering with Lawrence Berkeley National Laboratory on precursor designs to the WFIRST mission. Within the last year we have also become a major contributor to the Fermilab-led next-generation dark matter search experiment, the Super Cryogenic Dark Matter experiment (CDMS) for SNOLab. These experiments will keep SLAC at the forefront of particle physics and cosmology over the next decade. We look forward to working with the other HEP laboratories and the university community in pursuing the exciting dark energy and dark matter science program laid out by community planning over the last two years.

—David MacFarlane
SLAC Today, August 27, 2010