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In this issue:
New Accelerator Technique Doubles Particle Energy in Just One Meter
Science Today: A Universe without Weak Interactions
AAAS Conference Offers Broad View on Science

SLAC Today

Thursday - February 15, 2007

(Image - Energy acceleration)
The blue streak in this photograph shows the dramatic gain in energy made by some of the electrons in a bunch after passing through plasma (ionized gas). The white spot shows the electrons in the bunch that generated the plasma to propel the other electrons to double their energy, to 85 billion electron volts (GeV). 

New Accelerator Technique Doubles Particle Energy in Just One Meter

Imagine a car that accelerates from zero to 60 in 250 feet and then rockets to 120 miles per hour in just one more inch.

That's essentially what a collaboration of accelerator physicists has accomplished, using electrons for their racecars and plasma for the afterburners. Because electrons already travel at near light's speed in an accelerator, the physicists actually doubled the energy of the electrons, not their speed.

The researchers—from the Department of Energy's Stanford Linear Accelerator Center (SLAC), the UCLA Henry Samueli School of Engineering and Applied Science, and the University of Southern California Viterbi School Of Engineering—published their work in the February 15 issue of Nature.

This achievement demonstrates a technology that may drive the future of accelerator design. To reach the high energies required to answer the new set of mysteries confronting particle physics—such as dark energy and the origin of mass—the newest accelerators are vastly larger, and consequently more expensive, than their predecessors. Very high-energy particle beams will be needed to detect the very heavy and very short-lived particles that have eluded scientists so far.

"We hope that someday these breakthroughs will make future generations of accelerators feasible and affordable," said SLAC Deputy Director Persis Drell. "It's wonderful to see the tremendous progress in understanding the underlying physics for fundamentally new methods of accelerating particles."  Read more...

(Daily Column - Science Today)

A Universe without
Weak Interactions

One of the biggest problems facing theoretical particle physics since the discovery of the Standard Model is the hierarchy problem. The Standard Model explains why the weak interactions are so weak relative to electromagnetism. But in the Standard Model, it is hard to understand why the weak interactions are so strong relative to gravity. An idea that has recently become popular among theorists is that the weak interactions must be so strong because, through their role in setting the masses of known particles and also in the formation of chemical elements and stellar burning, they are essential to life. Recently, Graham Kribs of the University of Oregon, Gilad Perez of SUNY, Stony Brook, and I put forward a significant challenge to this idea by constructing an imaginary universe, suitable for life, in which the weak interactions play no role.

The strength of the weak force is determined by the mass of the W boson, which in turn is given by the expectation value or condensate of the Higgs field. If this value is much larger than the proton mass, the weak interactions will be weak.

AAAS Conference Offers Broad View on Science

The American Association for the Advancement of Science (AAAS) holds its annual meeting this weekend in San Francisco. This event has become one of the most important gatherings of the year for the science media and those interested in the interactions among disciplines and in the influence of science and technology on society.

Over 5,000 researchers and journalists are expected to attend the three-day conference. Attendees will have the opportunity to choose among a broad range of activities, including nearly 180 symposia as well as plenary and topical lectures.

Several SLAC researchers, including Dr. Burton Richter, will speak at the meeting. Click here for a full conference schedule.

The general public is invited to attend Family Science Days, plenary events, career workshops, and the exhibit hall. In addition, a town hall on "Communicating and Learning About Global Climate Change: An Event for Teachers, Students, and Other Communicators and Learners" is intended to expand the dialogue among scientists, teachers, students, policy-makers, business leaders, and the general public on the issue of global climate change.

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