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In this issue:
The Strong Future of FELs
Science Today: D Meson Mixing—Might it be New Physics?
House Appropriations Committee Backs Full DOE Science Request

SLAC Today

Thursday - June 14, 2007

In recent work carried out at DESY, researchers zapped a sample (left) with a single pulse to obtain a diffraction pattern (center). A computer algorithm processed the diffraction pattern in the center image to reconstruct the original image (right).

The Strong Future of FELs

The future of science at SLAC is changing, and much of that future lies in the field of x-ray science. This shift in focus, embodied by the Linac Coherent Light Source (LCLS) now under construction, parallels recent advances in x-ray science that stand at the leading edge of how we investigate the structure of matter. In this week's edition of the journal Science, researchers Kelly Gaffney of SLAC's Photon Ultrafast Laser Science and Engineering (PULSE) center and Henry Chapman of Lawrence Livermore National Laboratory detail how breakthroughs in x-ray imaging techniques are paving the way for a new kind of science.

Synchrotron accelerators have served as the foundation of light-source science for decades. Now, a new generation of linear-accelerator based free-electron lasers (FELs), such as the LCLS and the future European and Japanese x-ray FELs, are poised to take center stage. FELs have the advantage of creating extremely short pulses that are billions of times brighter than traditional x-ray sources, opening the door on investigations of phenomena too small or too fast to study with synchrotrons.

The review paper by Gaffney and Chapman outlines the future of x-ray science in the context of several recent experiments that serve as a preview of things to come. Last fall, researchers using the FLASH facility in Hamburg demonstrated the exciting potential of FELs by capturing a diffraction image of a micron-sized target using only a single pulse of photons. Another group of researchers, led by SLAC physicist David Fritz, recently demonstrated how ultra-fast laser pulses can be used to capture images of atoms in motion. These two techniques—single-shot and ultra-fast imaging—stand to revolutionize x-ray science.

On-site readers can access the full article at the SLAC Research Library website.

(Daily Column - Science Today)

D Meson Mixing—
Might it be New Physics?

One way to hunt for new physics beyond the Standard Model is to observe processes that are expected to be very rare. If the rates for rare processes are found to be higher, or lower, than what is predicted by the Standard Model, this gives a clear signal for the existence of new physics. A particularly important class of rare processes is known as meson mixing, where neutral mesons spontaneously transform into their own antiparticles. This transition occurs because of a property of quantum mechanics that allows virtual particles to pop in and out of existence.

We have already learned much from the rates of meson mixing processes. In the 1960's, the very slow rate of K meson mixing was a major problem for the theory of weak interactions. Glashow, Iliopoulos, and Maiani solved this problem by predicting the existence of the charm quark, which was later discovered at SLAC and Brookhaven. In the late 1980's, B mixing was discovered at DESY with a rate that seemed amazingly large. This was the first evidence for the very large value of the top quark mass. Now the Standard Model seems to explain both rates well, and theorists use these processes to obtain constraints on physics beyond the Standard Model, or perhaps even find evidence for new effects.

Last March, BaBar and Belle announced the discovery of mixing between the neutral D meson and its antiparticle. The D meson is a bound state of a charm quark with an anti-up quark. This discovery marked the first time that a rare process involving a charm quark transition had been observed! Experiments had been searching for decades for this process. Since rare D meson transitions had never before been detected, no theoretical model, not even the Standard Model, had been tested with processes of this type.

I found this very exciting and literally lay awake all night after the discovery was announced, thinking of the countless calculations one could do.  Read more...

House Appropriations Committee Backs Full DOE Science Request

The House Appropriations Committee has approved its version of the FY 2008 Energy and Water Development Appropriations Bill and sent it to the House floor for consideration later this week. Under this bill, H.R. 2641, the Bush Administration's request for the Office of Science for the upcoming fiscal year was fully funded.

An advance copy of the report (110-185) accompanying the bill sets forth the recommendations of the Energy and Water Development Appropriations Subcommittee. The subcommittee is chaired by Rep. Peter Visclosky (D-IN); the Ranking Minority Member is Rep. David Hobson (R-OH). Portions of this report follow (note that there is minor variance in numbers):


According to the committee report, the FY 2007 appropriation for the Office of Science is $3,797.3 million. The Bush Administration requested $4,397.9 million. The House Appropriations Committee would provide $4,514.1 million, an increase of 18.9 percent or $716.8 million over this fiscal year.

The report states:
"The Committee is generally pleased with the Department's budget request for the Office of Science in fiscal year 2008. This request for a 15.8 percent increase is the major incremental increase planned within the overall 10-year doubling of funding for these activities in DOE. A critical element of this increase is the support it will provide for 3,500 more research personnel, including graduate students. This addresses a major concern for the future of the United States economy, namely the availability of highly educated scientists and engineers to support the technical innovations that drive economic growth.


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