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Getting the Science Out: BaBarians Finish What They Start

BaBarians Sudan Paramesvaran (left) and Mike Sigamani. (Photo by Marissa Cevallos.)

A dose of supplemental funding from the Department of Energy is helping to finish crucial studies of BaBar data this year. Graduate students who have already defended their doctoral theses have been invited back to SLAC for a few months to polish their data analyses.

"The science coming out of BaBar is very interesting," said Mike Roney, the BaBar physics analysis coordinator who prepared the science case in the funding request. "These individuals are key to this science coming out."

The DOE funded five BaBar students this year to return to SLAC and finish additional work beyond the requirements to complete their PhDs. In the past, such leftover analyses often would be picked up and completed by incoming graduate students or postdocs, but since BaBar stopped collecting experimental data in 2008, fewer graduate students have been joining the collaboration. Because it is important for current students to wrap up their studies themselves, BaBar made a strong case to the DOE for supplemental funds. Each of the students has spent a few months tightening error calculations from their research, numbers that determine how confidently physicists can know a measurement.

"The DOE is invested heavily in BaBar," Roney said, and this is by comparison a modest but key contribution to get the science out.

The extra funding is beneficial not only to the BaBar collaboration, but also to students who get a chance to publish more research. Sudan Paramesvaran, a newly minted doctorate, is one of the fund recipients. He studies a particular decay of the tau lepton, a fundamental particle.

"It was a great opportunity to finish the work I started and get it published, before starting my postdoc," Paramesvaran said.

He's wrestling with the data to learn how often the tau lepton can decay into particles containing a strange quark. That number puts tighter limits on other fundamental physical processes that lie outside of particle physicists' Standard Model. Though a large number of BaBar analyses are ongoing, Paramesvaran is the only person in BaBar whose thesis is based on studying that particular decay.

Another student, Mike Sigamani, is measuring how often a bottom quark can change into an up quark, a number that is uncertain from previous studies. Pinning down the exact number is critical for understanding Charge-Parity violation, the Nobel prize-winning idea that matter and antimatter behave differently.

The DOE supplemental funding not only helps students make these cutting-edge measurements, it also helps to keep the BaBar group at SLAC energized.

"Bringing people here stimulates the intellectual environment," Roney said. "It feeds the general health of the collaboration and helps increase the publication output of what is already an extremely productive team of scientists."

—Marissa Cevallos
SLAC Today, May 12, 2010