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Brieflies...

First Events at B Factory: Physicists at the Stanford Linear Accelerator Center (SLAC) achieved a major milestone when they recently recorded the first collision in the new B Factory particle collider. Such collisions create short-lived subatomic particles called B mesons that help scientists better understand the fundamental principles underlying all matter. A principal goal of the B Factory is to study the phenomenon of CP violation — a difference between matter and antimatter. The first published results are anticipated by next year. SLAC is funded by the Office of High Energy and Nuclear Physics.

Contacts: Michael Riordan, SLAC, (650) 926-2613, michael@slac.stanford.edu; or David Salisbury, (650) 725-1944, david.salisbury@stanford.edu. For more information, see http://www.slac.stanford.edu/slac/media-info/pressphoto_bfactory.html

Noble Gas Isotopes Reveal Hydrocarbon History: Researchers at Lawrence Berkeley National Laboratory and the University of Connecticut have identified a signature of enriched xenon (Xe) gas associated with hydrocarbon sources at Elk Hills oil field in California. Analyzing noble gas isotopes at Elk Hills has provided a way to identify separate source regions and constrain hydrocarbon migration history—both of which are critical to understanding how oil is generated and trapped and for setting production strategies. Using noble gas geochemistry to quantify oil-gas-water interaction has important applications in mapping oil and gas migration pathways and delineating different hydrocarbon source regions. This research is supported by the Office of Basic Energy Sciences/Geosciences Research Program.

Contact: Mack Kennedy, LBNL, bmkennedy@lbl.gov or Tom Torgersen, UConn, torgerse@uconnvm.uconn.edu.

Gammasphere--Thanks for Sharing: The Gammasphere is a 12-ton gamma-ray microscope used to study the complex structure and behavior of nuclei. The nuclei studied with Gammasphere have been created in a heavy-ion induced fusion reaction where an accelerated projectile nucleus collides and fuses with a target nucleus to form a highly excited compound nucleus. These highly excited nuclei release their energy by emitting gamma rays — a form of extremely high-energy light. By measuring the energy of these emitted gamma rays with Gammasphere, researchers can gain insight into how the structure of nuclei change as both a function of proton and neutron number. Over a year ago, this $20 million national traveling physics instrument was moved from the 88-inch Cyclotron facility at Lawrence Berkeley National Laboratory to the ATLAS heavy-ion accelerator at Argonne National Laboratory to switch from a concentration of studying nuclei at "high spin" to studying the structure of exotic "nuclei far from stability."

Most of the experiments conducted using Gammasphere at Argonne have reached unique levels of sensitivity. In many instances, this has been made possible by coupling Gammasphere to the Fragment Mass Analyzer (FMA), a high resolution mass spectrometer that measures the mass of the residential nuclei produced in a heavy-ion reaction. By using Gammasphere and the FMA in tandem, structural and reaction-mechanism measurements have been made on No-254 (Z=102), the heaviest element ever studied by "in-beam" gamma-ray spectroscopy. In addition, information on the structure of nuclei lying at the limits of stability have been obtained. For example, by measuring excited states in proton emitter Ho-141 with Gammasphere, it has been independantly confirmed that this nucleus is deformed when the proton is emitted. In the same experiment, gamma-ray spectroscopy measurements were made on an isomer produced with a cross section of which is the lowest ever reported for this field of research.

Many more experiments are planned with the ATLAS accelerator at Argonne before the Gammasphere returns to Berkeley in March 2000. This research is supported by SC's Office of High Energy and Nuclear Physics.

Contact: Mike Carpenter, Argonne National Laboratory, (630) 252-5365, carpenter@anlphy.phy.anl.gov

Related Information:
"The Gammasphere Detector: Probing Nuclei at the Limits of Stability," http://www.phy.anl.gov/dnp/current/gamma/gs@limits.html
"Gammasphere Leads Explorers Along Rim of the Valley of Nuclear Stability," Logos, Vol. 16, No. 2, Winter 1998 — Online at http://www.anl.gov/OPA/logos16-2/gammasphere1.htm

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