Thursday - December 18, 2008
SLAC Today is
available online at:
http://today.slac.stanford.edu
In this issue:
BaBar Collaboration Completes Data Reprocessing
Science Today: R-Axion—A Flash from the World Beyond Supersymmetry
Guidelines for Updating Lab Name and Logo Items
Alpine Gate to Re-open
Gate 17 Holiday Closure
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Thursday - December 18, 2008 |
BaBar Collaboration Completes Data Reprocessing One might think that processing the records of 22 billion electron and positron collisions once would be enough. But not so for the BaBar collaboration, which this week announced the completion of reprocessing for 99.99 percent of its huge coffers of Upsilon(4S) raw data. Processing is one of the very first steps in data analysis, and involves putting raw data into a more useful form. This requires taking the signal recorded by BaBar's many layers of detectors and reconstructing which types of particles left the signals, while traveling in what directions and at what speeds. These reconstructed data are then compared to simulated data to identify particularly interesting events, and divided into many different streams from which researchers can pluck event types of interest. Over the years, the collaboration has again and again reworked the method and programs it uses to process data. By reprocessing the entire dataset with the newest software, the collaboration has now created a standardized dataset across the experiment's eight years of data collection. Read more... |
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R-Axion—A Flash from the World Beyond Supersymmetry
One of the main goals of the upcoming experiments at the Large Hadron Collider is the discovery of a new class of subatomic particles, supersymmetric particles. Supersymmetry is a postulated new symmetry of nature that could solve many of the current problems of elementary particle physics. For example, it could explain the nature of the Higgs boson and the identity of the particle that makes up dark matter. Many previous SLAC Today articles from the Theory Group have discussed methods for finding supersymmetry in collider experiments. (For example, see "Catch Me if You Can: Searching for Gluinos at the Tevatron.") What's next? If supersymmetry is realized in nature, it must be hidden so that the Standard Model looks perfect at the energies explored up to now. First of all, supersymmetric particles must be heavy. This requires that supersymmetry must be spontaneously broken by some mechanism—that is, there must be some natural difference between supersymmetric matter and ordinary matter. In addition, the masses and quantum numbers of supersymmetric particles must satisfy special relations that make the effects of these particles small in flavor-changing and CP-violating processes such as those measured by the BaBar experiment. These requirements constrain the manner in which supersymmetry can be broken. Many models have been proposed in which supersymmetry is broken in a tidy way without conflicting with the successes of the Standard Model. These successful models share two ingredients. The first is that supersymmetry is broken by new particles with no Standard Model interactions. These particles must be connected to quarks and leptons by some mediating interactions. In some models, gravity provides the connection. In other models, the new particles connect to the Standard Model photons, gluons, and W and Z bosons. Which model is the right one? To answer this question, physicists need to find ways to probe experimentally how supersymmetry breaking works. For most of the proposed models, the evidence on supersymmetry breaking is indirect. Scientists will look for clues in the details of the mass spectrum of supersymmetric particles, as observed at the LHC. However, there is a particular class of models of supersymmetry breaking that can provide a more direct glimpse of the hidden particles and their interactions. The crucial ingredient is a property of many supersymmetric models called R-symmetry. Read more... |
Guidelines for Updating Lab Name and Logo Items
With the launch of the new lab name and logo, the Communications Office has received a variety of questions regarding the creation of new materials and phasing out of old ones. In the interest of clearly and consistently using the new logo, please note the following guidelines: Print/external use: Existing print materials that bear the old SLAC name and logo should be phased out by April 1st. Print/internal use: Existing print materials for internal use, for example, forms, bearing the old SLAC name and logo should be used as-is until stocks run out. Web presence: The SLAC name and logo in electronic media, including Web pages and email signatures, should be updated on a timely basis as other priorities allow, using the new logo and usage guidelines. Business cards: A new template, to be made available the week of January 5th, will allow SLAC personnel to print new business cards locally using a color printer and Avery card stock. Alpine Gate to Re-open
At the start of Linac Coherent Light Source construction in June 2006, the Alpine Gate was closed to employees to allow access for the heavy construction equipment used by Turner Construction. With the recent completion of Turner's work, the gate will re-open beginning January 5, 2009. It will be open 6:00–10:00 a.m. and 3:00–6:00 p.m., Monday through Friday, for the morning and afternoon commutes. This gate will be useable by all lab personnel with a current SLAC badge. Construction subcontractors, visitors and staff without a badge will still need to check in at the Sand Hill Gate. Gate 17 Holiday ClosureGate 17 will be closed from 10:00 p.m. on Friday, December 19th through 10:00 p.m. on Sunday, January 4th. During this period, the few employees who are required to be on-site during the shutdown, and need access beyond this gate, can park in the lots near the gate and use the pedestrian turnstile located at Gate 17 and behind Building 137. Employees requiring vehicle access can use the Sector 30 gate and PEP Ring Road to access the area. The Sector 30 gate will be open 24/7. After return from the shutdown, Gate 17 will be open Monday through Friday from 6:00 a.m. until 10:00 p.m., until further notice. Access during other hours will be through the turnstile for pedestrians or through the Sector 30 Gate via PEP Ring Road. If you have any questions, please contact Security (x2551). |
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