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SLAC to Interpret ATLAS Data as Tier 2 Computing Center

Last summer, SLAC officially joined the collaboration working on ATLAS (A Toroidal LHC ApparatuS), one of the detectors being built for the Large Hadron Collider (LHC). Recently named a Tier 2 Computing Center, the lab now takes on an integral role in the global effort to analyze the onslaught of data expected from ATLAS once the LHC comes online later this year.

"This is the most exciting high energy physics you can do at this time," said Richard Mount, director of Scientific Computing and Computing Services and principal investigator of the lab's Tier 2 project. "The computing challenge is to thoroughly and rapidly analyze huge amounts of data. SLAC will try hard to play a major role in the success of ATLAS physics analysis."

SLAC is one of the few dozen Tier 2 institutions around the world and one of only five in the U.S. At the moment, the main role of a Tier 2 institution is to run simulations. Once the LHC turns on, the lab's role will expand to interpreting the data to glean a deeper understanding of physics at high energies.

The tiered computing system is a way of distributing and organizing data and computing resources for scientists around the world. CERN, the Tier 0 institution, will conduct the first round of reconstruction analysis, turning raw data into useful information such as particle mass and momentum. The data will then find their way to one of the 10 Tier 1 institutions around the world, including Brookhaven National Laboratory, the only such site in the U.S.  After multiple rounds of further refinement, the Tier 1 institutions will store the data on disk, giving users access to all stages of reconstruction. Tier 2 computing centers will then provide researchers with resources to analyze data. Scientists can also use their own computers at their respective research groups, labs, and universities, the third tier of the hierarchy.

SLAC is already using existing hardware to run simulations, but more computing power devoted to ATLAS is on its way. SLAC also has the capability to store large amounts of data, giving users the benefit of easy access, said Charlie Young, who, along with Su Dong, leads the ATLAS team at SLAC.

"As a national lab, one of our missions is to support users," Young said. "We'll be providing a center for the computing needs of ATLAS."

óMarcus Woo, February 21, 2007

Above image: SLAC's ATLAS team includes (left to right): Wei Yang, Booker Bense, Charles Boeheim, Leonard Moss, John Bartelt, Randal Melen. Not pictured are Richard Mount and Lance Nakata.