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In this issue:
From the Director of Particle Physics and Astrophysics: Mapping BaBar's Future
Making Magnetic Monopoles, and Other Exotica, in the Lab
Word of the Week: Luminosity

SLAC Today

Friday - January 30, 2009

(Photo - Steve Kahn)

From the Director of Particle Physics and Astrophysics: Mapping BaBar's Future

Last week, SLAC hosted a meeting of the International Finance Committee for BaBar. The IFC consists of representatives from the major funding agencies that contributed to the construction and operation of BaBar. The committee meets semiannually to review progress on the experiment, and to approve allocation of the operations common fund, which helps to defray ongoing expenses. The meeting gave the IFC a chance to take stock of how far BaBar has come, and where the project is headed over the next few years.

As most readers of SLAC Today are aware, last year's budget crisis forced the lab to terminate B Factory operations earlier than planned, after nine years of operation. The last run, stretching from late December 2007 until early April 2008, was among the most successful as characterized by the average luminosity, a measure of the number of electron-positron collisions obtained per unit time. Knowing that the run would be curtailed prematurely, the BaBar collaboration made the decision to alter the running conditions to explore new ground. Rather than tuning the beam energies to the same target (the Υ(4S) resonance, one of the excited states of the particle bottomonium), as had been done in all of the previous runs, they instead explored two additional resonances, using the extremely high luminosity of the PEP-II storage ring to gather data samples 12 and 20 times larger than previous experiments in only three months. This last run therefore provided a truly unique dataset, which is now revealing very exciting physics results.  Read more...

Making Magnetic Monopoles, and Other Exotica, in the Lab

Physicist Shou-Cheng Zhang has proposed a way to physically realize the magnetic monopole. In a paper published online in the January 29 issue of Science Express, Zhang and post-doctoral collaborator Xiao-Liang Qi predict the existence of a real-world material that acts as a magic mirror, in which the never-before-observed monopole appears as the image of an ordinary electron. If his prediction is confirmed by experiments, this could mean the opening of condensed matter as a new venue for observing the exotica of high-energy physics.

Zhang is a condensed-matter theorist at the Stanford Institute for Materials and Energy Science, a joint institute of SLAC National Accelerator Laboratory and Stanford University. He studies solids that exhibit unusual electromagnetic and quantum behaviors, with an eye toward their use in information storage. But due to his training as a particle physicist, Zhang always keeps the big picture in mind. That's why it was so easy for him to see that the material he was already working on could behave like what theorists call a magnetic monopole, an isolated north or south magnetic pole.

Read more in Symmetry Breaking...

Image courtesy of Sandbox Studio.

Word of the Week:

Luminosity is the term used to describe the effectiveness of a colliding-beam particle accelerator. In an electron-positron collider, luminosity is equal to the number of collisions per second, times the number of electrons in each bunch, times the number of positrons in each bunch, divided by the cross-sectional area of the beams. The tighter the beams are focused and the more particles are packed into each bunch, the higher the luminosity.


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