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In this issue:
SSRL Plays Major Role in Identifying Protein Structure
Science Today: BaBar Searches for Super-Penguins
Chinese Academy of Sciences Visits SLAC
Safety and Security Briefing Now Online
Texas A&M University Sponsors Next USPAS

SLAC Today

Thursday - September 14, 2006

SSRL Plays Major Role in Identifying Protein Structure

(Image - protein)
A graphical representation of a protein molecule from a common type of bacteria, posted to the Protein Data Bank by JCSG.

If the blueprint of life is DNA, then the building blocks it calls for are the proteins that make up living tissues. These proteins come in a vast menagerie of shapes and sizes, which can be arranged into families, numbering in the tens of thousands.

Over the last decade, scientists have mapped out the genomes of countless organisms, identifying all the genes and giving us a first glimpse of the secrets behind life's blueprints. However, until now, knowing the function of a protein, encoded by a particular gene, has often remained elusive.

Knowing a protein's structure and shape can tell us a lot about its function. Researchers at the Joint Center for Structural Genomics (JCSG) have taken up the task of mapping the structures of representative proteins from a diverse set of organisms. This monumental task is only just beginning, but progress is accelerating, according to Ashley Deacon, group leader for the Structure Determination Core, which is based at the Stanford Synchrotron Radiation Laboratory (SSRL).  Read more...

(Daily Column - Science Today)

BaBar Searches for Super-Penguins

Can a penguin bring down the reign of the Standard Model of particle physics? The success of the Standard Model is a great achievement, but not a complete one. It fails to provide answers about the origin of the universe, such as the abundance of matter and lack of anti-matter in the universe.

(Image - Penguin)
BaBar is looking for traces of super-penguins among ordinary penguin decays. The above image shows an ordinary penguin decay, in which a b decays into a W+ and an anti-quark (here a t). This anti-quark then emits a gluon, which in turn decays into an s-s quark pair. The original anti-quark meets again with the W+ to be transformed into an s quark.

(Image - Super penguin)
In the "super penguin" diagram above, particles including the t are replaced with particles beyond the Standard Model.

It's been known for over 20 years that any particle in the penguin loop (the U-shaped portion of the top diagram) can be replaced with a heavy, non-Standard Model particle. Such "super-penguins" can interfere with measurements of physical quantities like the charge-parity asymmetry parameter (sin2β). A deviation from the predicted value for sin(2β) would be a clear evidence of interactions beyond the Standard Model. Yet due to the rarity of penguin decays these experimental studies are difficult.

The BaBar experiment investigates many penguin decays of the neutral B-meson, such as the decay into three kaons B0->K+K-K0, which is one of the two most copious penguin decays. However, since this is a three-body decay, there are multiple paths that a B-meson can take to reach the final state, and depending on the path taken, the properties of the decay can be very different.

The most prominent path is through an intermediate, short-lived φ particle, the products of which are experimentally easy to reconstruct, and the properties of the final state φK0 allow a theoretically clean interpretation. Unfortunately, only 15% of the decays take this path.

Underneath the φK0 there is a much wider resonant state (f0(980)K0), and above it a sea of non-resonant decays and decays into wide scalar resonances, each potentially having a different charge-parity violation parameter.

In previous analyses, the presence of various decays with different properties was a great concern and a major source of systematic error. In our latest work, we use additional kinematic variables (known as the Dalitz plot) together with decay-time properties of the B meson to separate these intermediate states. Interference between the states carries important information too. Previous analyses could measure sin(2β) only, which has a two-fold ambiguity on the angle 2β. Utilizing interference effects, we extract additional trigonometric information and resolve this ambiguity better than 99.999%.

The latest results are intriguing. Although they are not a smoking gun for new types of interactions, they give lower values than expected, consistent with a trend seen in other penguin analyses. Search for super-penguin decays seems on track, although the particle-physics community will have to work harder to achieve it.

Chinese Academy of Sciences Visits SLAC

(Photo - CAS)
Click on image for larger version.

Senior members of the Chinese Academy of Sciences visited SLAC on Wednesday to learn about the unique relationship between SLAC and Stanford—a federal research lab and a major university.  Rachel Claus and Jerry Jobe gave presentations before the group toured the lab. 

Safety and Security Briefing Now Online

On September 7, SLAC held its annual Safety and Security Briefing. Video of the talks and PowerPoint slides are now available online.

Texas A&M University Sponsors Next USPAS

(Image - USPAS participants)
Students at the last winter session of the USPAS in January 2006 at Arizona State University.

Every year for roughly the past twenty years, the U.S. Particle Accelerator School (USPAS) has organized two-week-long summer and winter sessions, comprised of courses for the scientific and engineering communities in the field of particle physics, nuclear physics, basic energy sciences, fusion and related accelerator technologies. Providing specialized accelerator physics and engineering courses that are not often available at universities, the USPAS has helped train thousands of students over the years, including more than 500 international participants and more than 1600 individuals from Department of Energy and National Science Foundation laboratories. The average attendance at USPAS sessions is about 130 students. This year, Texas A&M University will sponsor the winter session of the USPAS in Houston, Texas from 15-26 January 2007.

In an effort to give students the opportunity to learn more about the ILC, USPAS has started to integrate multiple courses about linear colliders into their curriculum, including the upcoming school in January. "A general theme that underlies the Winter 2007 school session constitutes the physics and technology for linear colliders," said USPAS Director Bill Barletta. "We try to make sure that we have courses relevant to the linear collider at every session so that someone who is interested in participating in the ILC can get the information they need."

Highlights from this year's winter session with a focus on linear collider physics include a one-week course on Damping Ring Design and Physics Issues taught by Andy Wolski of the University of Liverpool and Cockcroft Institute. Also of interest to students pursuing ILC work would be a one-week course on beam preservation, Collective Effects and Wakefields, taught by Roger Jones of the University of Manchester and The Cockcroft Institute. This course might be paired with a course titled Beam Delivery System and Interaction Region of a Linear Collider, taught by Mauro Pivi and Andrei Seryi of SLAC and Nikolai Mokhov of Fermilab. GDE Director Barry Barish will also present a special evening lecture about the ILC.

"Our plan for every session is to include classes that will be critical for the linear collider," Barletta said. "We are betting our future in high energy physics on the ILC, and we need to make sure that there are students coming up."

Applications are due by 13 October 2006. Attendees for course credit may enroll to take either one two-week course or two one-week courses; auditors can attend one or both weeks. Participants in the US and abroad may apply for financial support, which includes lodging, student fee, meals and books. Due to visa procedures, foreign students may not receive course credit, but they may apply for financial aid pending a letter of recommendation from an advisor and acceptance by the USPAS. More information about USPAS is available online.

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