SLAC Today is available online at:
http://today.slac.stanford.edu

In this issue:
Fermi Gamma-ray Space Telescope and Namibia's HESS Explore a Blazar
BaBar Confirms Bottom-most Bottomonium
New SciDoc Authoring Tool to Replace iDoc
Workplace Violence Prevention Workshop Offered Tuesday

SLAC Today

Thursday - March 19, 2009

Fermi Gamma-ray Space Telescope and Namibia's HESS Explore a Blazar

(Image - blazar)
In the heart of an active galaxy, matter falling into a supermassive black hole somehow creates jets of particles traveling near the speed of light. For active galaxies classified as blazars, one of these jets beams right toward Earth. Credit: NASA/Goddard Space Flight Center Conceptual Image Lab. (Image courtesy of NASA.)

An international team of astrophysicists using telescopes on the ground and in space, including the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope, has uncovered surprising changes in radiation emitted by an active galaxy. The picture that emerges from these first-ever simultaneous observations with optical, X-ray and new-generation gamma-ray telescopes is much more complex than scientists expected and challenges current theories of how the radiation is generated.

The galaxy in question is PKS 2155-304, a type of object known as a "blazar." Like many active galaxies, a blazar emits oppositely directed jets of particles traveling near the speed of light as matter falls into a central supermassive black hole; this process is not well understood. In the case of blazars, the galaxy is oriented such that we're looking right down the jet.

PKS 2155-304 is located 1.5 billion light-years away in the southern constellation of Piscis Austrinus and is usually a detectable but faint gamma-ray source. But when its jet undergoes a major outburst, as it did in 2006, the galaxy can become the brightest source in the sky at the highest gamma-ray energies scientists can detect, up to 50 trillion times the energy of visible light. Even from strong sources, only about one gamma ray this energetic strikes a square yard at the top of Earth's atmosphere each month.

Gamma rays at lower energies were detected directly by the Large Area Telescope. "The launch of Fermi gives us the opportunity to measure this powerful galaxy across as many wavelengths as possible for the first time," says Werner Hofmann, spokesperson for the H.E.S.S. team at the Max-Planck Institute for Nuclear Physics in Heidelberg, Germany.

Read more in the full NASA news release...

BaBar Confirms Bottom-most Bottomonium

(Photo - Chris West)
Researcher Chris West reads about BaBar. (Photo by Brad Plummer. Click for larger image.)

New results from the BaBar experiment confirm the collaboration's detection of the bottomonium ground state particle, the ηb (pronounced eta-sub-bee). Last summer, at the end of the experiment's final months of data taking, BaBar scientists found the elusive particle amid the decay of a more energetic bottomonium state called Y(3S). The new results uncover the ηb in the decay of another variant of bottomonium, the Y(2S) state.

The existence of ηb was predicted by theorists thirty years ago, but could not be confirmed experimentally until the BaBar result last year. Theory predicts that ηb should be a byproduct of the decay of both Y(3S) and Y(2S). BaBar was the first experiment to produce and analyze experimental data that could confirm it.

"[The Y(2S) result] gives more evidence that what we've discovered is actually the ηb," said SLAC graduate student Chris West, one of the key analysts in the finding. The two data sets are consistent in their measurement of the mass of the ηb, confirming that they are observing the same particle. Given the Y(3S) data, theory predicts a certain number of ηb events in the Y(2S) data, and the actual yield was consistent with those predictions. While the Y(3S) results are strong enough to stand alone, the new finding reinforces the original, and provides more information about the ηb. SLAC scientist and BaBar member Peter Kim announced the results at a meeting in December, and the collaboration recently approved a paper for journal submission.

Read more about ηb in the original ηb press release and Symmetry magazine.

(Image - SciDoc user interface)
(Click image to access SciDoc.)

New SciDoc Authoring Tool to Replace iDoc

Did you know that SLAC has a scientific and technical document repository that is accessible worldwide? As SLAC expands into new scientific realms, more robust tools are essential to help manage, disseminate and protect intellectual property. With this in mind, InfoMedia Solutions created SciDoc, SLAC's new scientific document repository. SciDoc replaces iDoc, the former document registration system, and offers many new features to make authors' work easier.

The MySciDoc personalized gateway provides quick registration, upload of new and revised documents, and real-time viewing and access to your documents. Even searching is improved, with full-text, metadata and citation information search capabilities. For questions and comments, please contact Document Services.

Workplace Violence Prevention Workshop Offered Tuesday

The workshop "Preventing Violence in the Workplace" will be presented on Tuesday, March 24, from 9:30 to 11:00 a.m. in the Redwood Conference Rooms, Building 48. Dr. Stephen White, President of Work Trauma Services, will help participants to recognize the warning signs of potential violence and provide practical information on what and how to report in cases of actual or threatened violence. SLAC policies and procedures for dealing with workplace violence will also be reviewed.

All supervisors and managers are encouraged to attend this timely and important training opportunity. Please register on the training Web site. Enter key search: VIO.

Events (see all | submit)

Access (see all)

Announcements
(see all | submit)

 Lab Announcements

Community Bulletin Board

Training (see all | register)

News (submit)

dividing line
(Office of Science/U.S. DOE Logo)

View online at http://today.slac.stanford.edu/.