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In this issue:
Theorists Reveal Path to True Muonium
Colloquium Today: Dark Matter Candidates and Signals
New "Brown Bag" Series on Finance Planning

SLAC Today

Monday - June 1, 2009

Theorists Reveal Path to True Muonium

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In this artist's depiction of how experimentalists could create true muonium, an electron (blue) and a positron (red) collide, producing a virtual photon (green) and then a muonium atom, made of a muon (small yellow) and an anti-muon (small purple). The muonium atom then decays back into a virtual photon, then a positron and an electron. Overlaying this process is a figure indicating the structure of the muonium atom: one muon (large yellow) and one anti-muon (large purple). (Graphic: Terry Anderson.)

True muonium, a long-theorized but never-seen atom, might be observed in future experiments, thanks to recent theoretical work by researchers at the Department of Energy's SLAC National Accelerator Laboratory and Arizona State University. True muonium was first theorized more than 50 years ago, but until now no one had uncovered an unambiguous method by which it could be created and observed.

"We don't usually work in this area, but one day we were idly talking about how experimentalists could create exotic states of matter," said SLAC theorist Stanley Brodsky, who worked with Arizona State's Richard Lebed on the result. "As our conversation progressed, we realized 'Gee… we just figured out how to make true muonium.'"

True muonium is made of a muon and an anti-muon, and is distinguished from what's also been called "muonium"—an atom made of an electron and an anti-muon. Both muons and anti-muons are created frequently in nature when energetic particles from space strike the earth's atmosphere. Yet both have a fleeting existence, and their combination, true muonium, decays naturally into other particles in a few trillionths of a second. This makes observation of the exotic atom quite difficult.

In a paper published this week in Physical Review Letters, Brodsky and Lebed describe two methods by which electron–positron accelerators could detect the signature of true muonium's formation and decay.  Read more...

Colloquium Today:
Dark Matter Candidates and Signals

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A quarter of the Universe is composed of dark matter, but what exactly dark matter is, no one knows. UC Irvine Professor of Physics and Astronomy Jonathan Feng will review recent progress in resolving this puzzle, focusing on several well-motivated possibilities, including WIMPs (weakly interacting massive particles) and related candidates. Feng will discuss the theoretical motivations for these candidates, their diverse implications at the interface of particle physics and cosmology, and the prospects for identifying dark matter in the coming years.

Feng's research interests combine theoretical particle physics, astroparticle physics and cosmology. He studies the universe at the smallest and largest length scales, with the goal of answering fundamental questions as to the existence of supersymmetric particles and extra spatial dimensions, and the nature of dark matter, dark energy and high-energy cosmic rays.

Feng's talk will take place at 4:15 p.m. today in Panofsky Auditorium. The colloquium is free and open to all.

Next Monday, Stanford Professor of Political Science Scott Sagan will present "Nuclear Power without Nuclear Proliferation?"

New "Brown Bag" Series on Finance Planning

The Strategic Financial Planning Office, in collaboration with the LCLS, Operations, SIMES and SSRL Planning Offices, is starting a series of brown bag meetings the first Wednesday of each month from noon to 1 p.m. in Building 41's Yellow Room. The meetings will focus on exchanging information, tips and tricks that are useful for financial management analysis at SLAC.

The first meeting will take place this Wednesday, June 3. For more details, see the full announcement.

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