A joint Fermilab/SLAC publication

On neutrinos and nanoseconds: Physicists partner with professional timekeeper


Professional timekeeper Demetrios Matsakis does not wear a watch. Image: Amy Dusto

When Demetrios Matsakis, the head of the U.S. Naval Observatory department that deals with measuring time, received an email from a Fermilab physicist in late September, he had immediate suspicions. The physicist asked if a two-way satellite transfer, one of the Naval Observatory’s specialties, would work in a particular timing measurement.

“This is about neutrinos, isn’t it?” Matsakis wrote back. Yes, it was.

Matsakis, head of the Time Service Department, soon found himself advising physicist Carl Rosenfeld and his partners on MINOS, a Fermilab neutrino experiment. This year another neutrino experiment, called OPERA, found the subatomic particles seemed to beat the speed of light while traveling between CERN in Switzerland and Gran Sasso National Laboratory in Italy. This is considered impossible under special relativity. The MINOS collaboration plans to double-check the OPERA experiment's result.

While on a personal trip to Europe this week, Matsakis stopped by CERN and met with OPERA researcher Dario Autiero, who first presented the perplexing neutrino results on Sept. 23.

Matsakis did not wear a watch on his trip to CERN, nor has he ever. He’s like many people in that he doesn’t want “to be ruled by time,” he said. Instead, Matsakis does the ruling.

In his job, Matsakis keeps the official time for the United States and the U.S. Department of Defense and, together with the National Institute of Standards and Technology, keeps the official time for the United States. This involves maintaining more than 100 atomic clocks and GPS systems calibrated to within one nanosecond of each other – not a simple task.

“A good cesium clock on a bad day can be off by five nanoseconds,” he said. In terms of GPS, one nanosecond can translate to being off in position on the ground by one meter. About 30 people work under him to take care of the time.

Together Matsakis and Autiero reviewed electronic timing systems and discussed all sorts of little details that could affect the measurements of the times neutrinos left CERN and arrived at Gran Sasso.

“There’s a lot I don’t know,” Matsakis said. One thing he learned about at CERN was the idea of a blind measurement in calibrations: Neither of two groups measuring separate clocks knows in advance what time they should see, so they don’t make any corrections until after comparing results and noticing a discrepancy. Matsakis isn’t sure whether this is a better method than just correcting a clock as soon as one realizes it doesn’t give the right time, but he’s open to trying it.

When he gets home, he and his counterparts at NIST will advise MINOS on their next steps in developing a better timing system. “I’m giving them a detailed shopping list, down to what model, what part and what company,” he said in a car ride between experimental sites he was touring with Autiero.

“Just in time for Christmas,” Autiero joked.

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