DOE Pulse - Science and Technology Highlights from the DOE National Laboratories

Berkeley Lab's Evan Mills holds a prototype white light-emitting diode.

The DNA Capture Element instrument was developed at the Pacific Northwest National Laboratory for the Air Force Research Laboratory. The "green box" is used to process samples of agents – in a matter of minutes – to determine if they are or aren't harmful.

Science 'detective story' sparked Seryi's career


Andrei Seryi

It was a book about element 104, known as Rutherfordium, which led a 12-year-old Andrei Seryi to pursue a career in physics. “It read like a detective story,” said Seryi, who now co-leads an inter national group of over one hundred people on the Internationall Linear Collider (ILC) beam delivery design team from the DOE's Stanford Linear Accelerator Center (SLAC).

Seryi obtained his Ph.D. from the Budker Institute for Nuclear Physics, where he helped design VLEPP, an electron-positron linear collider. His role was to devise the final focus system.

Now, 17 years later, he's doing the same thing. Currently, Seryi, Tomoyuki Sanuki from the University of Tokyo, and Grahame Blair from the Royal Holloway University of London are leading an international group of particle physicists working on the design of a final focus for the ILC, a future polarized electron-positron linear collider that will create collisions with energies from 500 GeV to 1 TeV. This time, however, the challenge is much more difficult.

When the electron and positron beams collide, the particle beams are severely disrupted and particles may be deflected into the detectors located around the collision point. In order to prevent such a scenario which will degrade the detector performance, Seryi and his group are designing a unique configuration for the final focus systems located at the ends of the two twenty-kilometer linear accelerators in the ILC. The particle beams will not collider head-on; instead, they will collider at an angle that is less than 180 degrees. Deciding exactly what the crossing angle will be, however, is the team's main task. "The international group is very active and able to work quite productively," says Seryi, who is excited about SLAC's role in the ILC.

“I think SLAC has a lot of expertise in a wide variety of areas and will play a central role in the ILC,” he said. “Certainly SLAC will play a large role in the beam delivery and final focus design.”

Submitted by DOE's Stanford Linear Accelerator Center

Theory meets experiment as Fermilab scientists team up for ILC


Fermilab theorists Marcela Carena (pictured) and Ayres Freitas are working with experimenters from the Fermilab, from Lancaster University in the UK , and from DESY-Zeuthen in Germany to develop a "benchmarking" process for detectors at the proposed International Linear Collider.

Together with four experimenters from DOE's Fermilab, from Lancaster University in the UK and from DESY-Zeuthen in Germany, Fermilab theorists Marcela Carena and Ayres Freitas are studying a possible "benchmarking" process for detectors at the proposed International Linear Collider.

The six scientists are investigating whether an ILC detector could measure the properties of "stop" quarks, hypothetical particles predicted by Supersymmetry. An ideal detector would be able to distinguish all interesting particles and processes from the collisions' background. But in the real world, experimenters must make compromises in building detectors. Theorists and experimenters work together and carry out computer simulations to test the capabilities of various detector designs.

" 'Stops' are of great theoretical interest," says Freitas. "If they exist and if they are light enough, they must have played an important role in the formation of matter in the early universe. They would have an effect on the total amount of dark matter."

Electron-positron collisions at the ILC would produce pairs of stop quarks, which would yield a signal of two charm quark jets and missing energy. Detecting these decays and concluding the existence of stop quarks is an experimental challenge.

"Anything else that creates two jets and large missing energy is a severe background," said Caroline Milstene, one of the four experimenters working on the project, during her presentation of the study at Fermilab in May. "We have to get rid of background that is a few orders of magnitude bigger than the signal."

The team showed that the ILC detector could determine the mass of a potential 122.6 GeV "stop" quark with a precision of +/- 0.4 GeV. Combined with other precision measurements, they found that the ILC can test whether supersymmetric particles are the source of dark matter. The study will be published later this year.

Submitted by DOE's Fermilab