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In this issue:
Construction Zones Remain Off-Limits
Science Today: New Measurement of the Unitarity Triangle
SLAC to Conduct Sitewide Business Continuity Study
John Weisend Takes His Leave—For Now

SLAC Today

Thursday - June 21, 2007

Construction Zones Remain Off-Limits

Linac Coherent Light Source (LCLS) construction activities at SLAC have been roaring on for months. Although it may be tempting to venture a peek behind the fence, the fevered activities at the job site make it a place of extraordinary danger for unauthorized persons. All construction zones are clearly marked and access regulations will be strictly enforced.

As a reminder, the construction site is strictly off limits to everyone unless accompanied by a LCLS University Technical Representative (UTR). The site is not available for tours. If you have official business and need access to the job site, please contact Lee Anne DeWan at the LCLS Conventional Facilities Main Office (x4400) for more information.

Even with an escort, the correct Personal Protective Equipment (PPE) must be worn at all times. PPE at a minimum includes steel-toed boots, reflective vest, hard hat and safety glasses, but special gear may be required as the construction environment varies. In addition to proper PPE and escort, access to the tunnel is limited only to those who have completed the proper tunnel safety training.

(Daily Column - Science Today)

New Measurement of the Unitarity Triangle

(Image - Unitarity Triangle)
The unitarity triangle.
(Image courtesy of CKMfitter collaboration.)

Using information obtained from detailed studies of B meson decays to K*0rho+ and rho+rho- can teach us about the tiny difference between matter and anti-matter. Our understanding of this phenomenon is encoded in three angles of a special triangle, called the unitarity triangle. These angles are called beta, alpha, and gamma. BaBar physicists have been able to constrain the second angle of the unitarity triangle to within seven degrees. This result is the culmination of over five years of work by BaBar in the pursuit of the angle alpha.

SLAC's B-factory was built to understand nature's preference of matter over anti-matter. The first landmark discovery in 2001 from the SLAC B-factory was the measurement of beta, which established that an asymmetry exists in the decay of B mesons versus the decay anti-B mesons. Particle and anti-particle decay at different rates. The angle beta is now measured to one degree by the BaBar and Belle experiments. Three years ago, BaBar released a result that laid down a proof of principle for measuring the second angle alpha using a previously neglected method, the decay of a B meson to a rho+rho- final state.

The elusive signal occurs one in forty thousand times. As every interesting signal event is swamped under a further 50 background events, this is a very challenging measurement to embark upon. BaBar has recently released a new measurement of this decay. Starting from a sample of almost four hundred million B meson pairs BaBar physicists have isolated 730 signal events that tell us something about the matter anti-matter difference. Performing this analysis is like searching for a needle in a haystack, and then trying to thread the needle once it has been found. If that is not challenging enough, there is a further complication to measuring alpha. This complication comes from troublesome loop contributions. These are additional ways to go from the initial B meson to the rho+rho- final state that quantum mechanically interfere with the interesting part of our signal.

The loop contributions are very rare, in this case occurring about nine times in every million B decays. That makes them hard for experimentalists to see. It is also hard for theorists to accurately calculate what we should expect to happen. The contamination to our precise measurement of alpha from these loop contributions is important, and it has to be well understood. Prompted by recent measurements of these rare loop processes, theorists have outlined a new method to constrain the loop contributions to rho+rho-Read more...

SLAC to Conduct Sitewide Business Continuity Study


What happens if a severe natural disaster strikes SLAC, if critical equipment fails, or if a vital materials supplier shuts down? To prepare for these and other possible business interruptions, the ES&H Division has initiated a site wide business interruption analysis that will be used to create a site emergency recovery plan, also known as a "Continuity of Operations" plan.

Business interruption analyses are a standard practice in industry; they reveal where and how a site's critical operations might be most vulnerable to disruption. While rare, severe disruptions do happen: SLAC experienced a site blackout in May of 2005. A tree in the Santa Cruz Mountains fell on SLAC’s primary power supply lines at a time when SLAC's secondary power lines were already down to accommodate off-site construction work. Electric power was cut off for three days.

The recovery plan will be used as a guide to minimize the effect of the most severe foreseeable events on SLAC’s operations and to plan the steps needed for a quick recovery. The plan will also help meet the requirements of a new draft Department of Energy (DOE) Order, DOE-O-150.1, "Continuity Programs," and will be used in conjunction with a companion recovery plan developed for the DOE Stanford Site Office.

ES&H will be assisted in this process by consultant Stephen Stoll, who has extensive experience in creating recovery plans for both industrial plants and government research facilities. As part of the analysis, Stoll and Ralph Kerwin of the ES&H Fire and Emergency Management group are circulating questionnaires this month to selected departments and will be interviewing a variety of SLAC employees ranging from top management to line personnel. Contact Kerwin if you are involved in the process and have questions. The full business interruption analysis and recovery plan preparation process is expected to last approximately three months and will be repeated periodically to further refine the information and keep it up to date.

John Weisend Takes
His Leave—For Now


John Weisend (center) with his family at the Sector 6 picnic area yesterday. (Image courtesy of Diana Rogers.)

John Weisend, who will take a temporary position at the National Science Foundation (NSF) in Virginia beginning later this month, said goodbye to friends and colleagues yesterday afternoon with a barbeque.

We'll leave the parting words to Ryan Auer, who sang at the event.

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