Feature: In Search of the Subtle and Rare
Three trillion times per second — that's how fast quarks in the B sub s (Bs) particle “oscillate,” or switch between their matter and antimatter states, according to scientists from the Collider Detector at Fermilab collaboration. The CDF physicists measured this rapid oscillation with the help of the world's most powerful particle accelerator, Fermilab’s Tevatron, unprecedented computing power made available through the Open Science Grid and the LHC Computing Grid, and a healthy dose of ingenuity.
“Bs oscillation is a very subtle and rapid effect,” says Jacobo Konigsberg from the University of Florida, co-spokesperson for the CDF collaboration. “It's astonishing that we can measure it at all.”
Astonishing as it may be, CDF routinely measures phenomena both subtle and rare. Recently, CDF researchers caught the rare and elusive Sigma sub b (Σb) particle using massive amounts of computing power and a clever, precise selection mechanism that allows data interesting to the physicists to be separated from that created by well-known particles and processes.
Both recent discoveries are significant because they provide exacting tests of, and also affirm, predictions from the Standard Model, a well-established, widely-applicable theory of fundamental particles and how they interact.
As CDF scientists seek to discover ever-rarer particles and processes, they need ever-greater amounts of data. In turn, they need ever more simulations of the passage of fundamental particles through the CDF detectors. These simulations show physicists which signals from the detector correspond to which particles and interactions, and how likely they are to be misled by fluctuations in their data that mimic real signals.
“CDF has been able to move all the simulation to resources on the grid and thereby complete it in a timely fashion,” says Pavel Murat, a CDF researcher from Fermilab.
CDF developed a distributed computing system on the Fermilab site several years ago. This system has now evolved to include Open Science Grid sites and to interface with the LHC Computing Grid. The CDF user interface has remained unchanged, allowing physicists to easily transition to using grid sites.
“Our physicists are submitting jobs to the grid sites on a daily basis without thinking about what resources are on the back end,” says Duke University’s Ashutosh Kotwal, a member of the CDF collaboration.
Today CDF is actively using five grid sites, has five more in the works, and will continue to expand its grid usage. The resources made available through Fermilab and the grid sites are currently sufficient to handle their data simulation needs.
“CDF will continue to probe the Standard Model to find its flaws and what might lie outside,” says Fermilab’s Rob Roser, CDF collaboration co-spokesperson. “These recent measurements, as remarkable as they are, are just two on the path down a very rich physics program in which we will continue to measure rarer and rarer phenomena.”
- Anne Heavey, iSGTW Editor