Thursday - July 31, 2008
SLAC Today is
available online at:
http://today.slac.stanford.edu
In this issue:
GLAST Logs Gamma Bursts During Fine Tuning
Science Today:
Prelude to the Higgs: Fermilab Observes Rare ZZ Diboson Production
SLAC Summer Institute Registration Deadline
Safety Review: Performing Work Within Controls
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Thursday - July 31, 2008 |
GLAST Logs Gamma Bursts During Fine Tuning Plot of a gamma-ray burst captured by the GLAST Burst Monitor on July 23. This powerful burst lasted over 50 seconds and was captured by each of the instrument's 14 detectors.
Photo courtesy of NASA. Larger image.
While only in orbit for 40 days and still in the process of a two-month checkout, NASA's Gamma-ray Large Area Telescope (GLAST) has already detected 12 powerful gamma-ray bursts, an encouraging harbinger of good things to come for this mission. The gamma-ray bursts were detected by the GLAST Burst Monitor (GBM), one of two instruments on the spacecraft. “We are thrilled to be detecting gamma-ray bursts so early in the mission. GLAST and the GBM are off to a great start!” said Charles “Chip” Meegan, GBM principal investigator at NASA’s Marshall Space Flight Center, Huntsville, Alabama. “The detectors are working well and we’re really pleased with how the instrument is working. That said, we’re using this checkout period to scrutinize the data coming down from the detectors and fine tune flight and ground software and our daily operational processes.” GLAST will observe gamma rays ranging in energy from a few thousand electron volts to many hundreds of billions of electron volts or higher, the widest range of coverage ever available on a single spacecraft for gamma ray studies. By detecting gamma-ray bursts, GBM will help GLAST crack the mysteries of these stupendously powerful explosions. Read more on NASA's GLAST mission Web site... |
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 Prelude to the Higgs: Fermilab Observes Rare ZZ Diboson Production
Scientists of the DZero collaboration at the US Department of Energy’s Fermilab have announced the observation of pairs of Z bosons, force-carrying particles produced in proton-antiproton collisions at the Tevatron particle collider. The properties of the ZZ diboson make its discovery an essential prelude to finding or excluding the Higgs boson at the Tevatron. The observation of the ZZ, announced at a Fermilab seminar on July 25, connects to the search for the Higgs boson in several ways. The process of producing the ZZ is very rare and hence difficult to detect. The rarest diboson processes after ZZ are those involving the Higgs boson, so seeing ZZ is an essential step in demonstrating the capability to see the Higgs. The signature for pairs of Z bosons can also mimic the predicated Higgs signature for large values of the Higgs mass. For lower Higgs masses, the production of a Z boson and a Higgs boson together, a ZH, makes a major contribution to Higgs search sensitivity, and the ZZ shares important characteristics and signatures with ZH. The ZZ is the latest in a series of observations of pairs of the so-called gauge bosons, or force-carrying particles, by DZero and its sister experiment, CDF. The series began with the study of the already rare production of W bosons plus photons; then Z bosons plus photons; then W pairs; then WZ. The ZZ is the most massive combination and has the lowest predicted likelihood of production in the Standard Model. Earlier this year, CDF found evidence for ZZ production; the DZero results presented on Friday for the first time showed sufficient significance, well above five standard deviations, to rank as a discovery of ZZ production. “Final analysis of the data for this discovery was done by a thoroughly international team of researchers including scientists of American, Belgian, British, Georgian, Italian and Russian nationalities,” said DZero cospokesperson Darien Wood. “They worked closely and productively together to achieve this challenging and exciting experimental result.” DZero searched for ZZ production in nearly 200 trillion proton-antiproton collisions delivered by the Tevatron. Scientists used two analyses that look for Z decays into different combinations of secondary particles. One analysis looked for one Z decaying into electrons or muons, the other decaying into “invisible” neutrinos. The neutrino signature is challenging experimentally, but worthwhile because it is more plentiful. In the even rarer mode, both Z bosons decay to either electrons or muons. Just three events were observed in this mode, but the signature is remarkably distinctive, with an expected background of only two tenths of one event. |
SSI Registration Deadline TomorrowThe SLAC Summer Institute begins Monday. Early registration ends today! Please register if you wish to attend any of the lectures, topical conferences or discussions. Safety Review: Performing Work Within ControlsThis article is the fourth in a five-part series examining each of the five core functions of SLAC's Integrated Safety Management System. The core functions are hands-on tools to help you plan and conduct work in a safe manner. Their relationships are depicted in this handy diagram:
Performing work within the safety controls for a given job, task or activity is the fourth core function in the ISMS safe work cycle. It builds on the strengths of the first three core functions, Defining Scope, Analyzing Hazards and Developing and Implementing Hazard Controls, covered earlier this week. Performing your job in a safe and minimal-risk manner requires that the work be done solely within the allowances of the formal authorization for the job. Deviation from a formal work authorization (cited by the Department of Energy as evidence of unacceptable 'expert-based work') can put your colleagues and yourself at elevated, unnecessary risk. Accidents, injuries, illnesses and property damage can easily result if team members vary from their work plan. Everyone at SLAC intends to work safely. But it can be tempting to think that a quick, small variation from the work plan will save time, money or aggravation. It won't. It could easily produce the opposite. For example, consider the task: welding a girder. Turning up a welding device might seem like a way to 'get this job done in half the time,' but in reality it could cause a fire and worse. If you find reason to change your planned workflow, stop the work and begin the ISMS process again. Reach a formal consensus with your supervisor before proceeding anew. Supervisors, please discuss this core function with your team members. Ask them to choose an example job, run it through the first three core functions, then apply this function by emphasizing the need to stay within approved work plans when doing the work. This will be one more important step toward leading everyone at SLAC to think of safety as an integral part of the work day. Tomorrow's article will discuss the fifth core function, "Feedback and Improvement." See the Integrated Safety and Environmental Management Systems Web site for more helpful hints. Please call Steve Frey (x3839) if you have any questions. |
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