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In this issue:
LCLS—Creating a Revolution in X-ray Science
Symmetry Explains It in 60 Seconds: Charged Leptons

SLAC Today

Friday - March 11, 2011

LCLS—Creating a Revolution in
X-ray Science

The second annual workshop on science with free-electron lasers, sponsored by the Max Planck Society, was held last week in the society's conference center at Schloss Ringberg in the Bavarian Alps south of Munich. This has become an annual, informal opportunity for researchers using Linac Coherent Light Source, FLASH and other facilities to meet for three days in an isolated mountain castle to discuss the problems and revolutionary opportunities of the new generation of X-ray laser light sources. The spectacular LCLS results just published last month in Nature on nanocrystallography and single-particle imaging of viruses were old news at this meeting, where the "buzz" was much more focused on the new data that has been collected since last summer. LCLS featured very prominently in many of the scientific presentations. These are the not-yet published results that will create headlines in the coming year. The talks were filled with images that were even more impressive than the snowy Alpine mountain scenery on view through the windows in the back of the lecture hall.

Jim Welch presented the current status of LCLS and future plans and vision for LCLS-II, and there were also talks on the status of the European XFEL and Spring-8 sources currently under construction. There were a number of other participants from SLAC, who presented several talks. John Bozek spoke about the LCLS Atomic, Molecular and Optical science instrument and recent results. Bill Schlotter described single-shot correction for timing jitter with soft X-rays. Christoph Bostedt talked about imaging ultrafast processes in clusters. Marco Cammarata gave an update on the first hard X-ray experiments at the X-ray Pump Probe instrument and one of us (Phil Bucksbaum) discussed recent AMO X-ray experiments in small molecules. The contingent of scientists associated with SLAC and LCLS experiments would likely have been even larger, except for ongoing LCLS experiments at the newly commissioned Coherent X-ray Imaging instrument.  Read more...

Malware Warning

There will be some e-mails scams and malware circulating regarding the recent Japanese earthquake that occurred overnight and of the tsunami effects around the Pacific including Hawaii and the West Coast of the U.S. Read more...

Symmetry Explains It in 60 Seconds: Charged Leptons

(Image - poodles)
(Image: Sandbox Studio.)

Charged leptons are a breed of elementary particle that comes in three masses: the lightweight electron, responsible for the electricity in our homes; the middle-weight muon; and the heavy tau. Two other types of elementary particles, quarks and neutrinos, come in three masses as well.

You might not think about dogs while you wonder about particle physics, but there are similarities. Poodles, for example, also come in three sizes—toy, miniature and standard—but they're all the same breed, and genetically similar. Learning how poodles and other breeds are related helps us understand the rules of dog genetics.

We want the same type of understanding of how elementary particles relate to one another. Quarks can change from one type to another; so can neutrinos. If you want to have any sensible "laws of genetics" for particle physics, that last breed, the charged leptons, had better be able to change types as well. That's called charged lepton flavor violation. Surprisingly, physicists have never seen it happen.

Previous experiments have looked at about 10 trillion muons; Fermilab's Mu2e experiment will observe 10,000 times more data, looking for a change from a muon to an electron. Discovering this change would point us toward a single theory explaining the genetics of the particles born in the big bang. If we don't discover this change, there will be a lot of head-scratching (as opposed to fur-scratching) as we try to understand the rules of the universe.

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