Evidence of faster-than-light particles puts IU theoretical physicist in spotlight
Whether physicists in Europe recorded a timing error in the billionths-of-a-second range or actually evidenced particles traveling faster than light, the Sept. 23 announcement had the phone ringing off the hook in the office of Alan Kostelecky, Indiana University Bloomington distinguished professor of physics.
Kostelecky's research investigates the possibility that a unified theory tying together quantum physics and gravity could lead to tiny but observable deviations from Einstein's Theory of Relativity. As part of this effort more than 25 years ago, Kostelecky and colleagues theorized in the paper "The Neutrino as a Tachyon" that neutrinos might travel faster than light.
So when physicists working in Italy with the particle detector Oscillation Project with Emulsion-tRacking Apparatus (OPERA) announced they had recorded neutrinos traveling 60 nanoseconds faster than the speed of light during a 730-kilometer trip from the CERN laboratory in Geneva, Switzerland, back to OPERA, it spurred renewed interest in Kostelecky's predictions that space-time might not look the same in all directions and that Albert Einstein's Standard Model portion of the Theory of Relativity could need some expansion.
In Kostelecky's Standard Model Extension (SME), proposed in the mid-1990s, relativity is not exact and there could be minuscule yet measurable violations where space-time does not look the same in all directions and instead exhibits preferred directions caused by a background field in the vacuum. The SME was created at IU in the mid-1990s and has been developed extensively in the intervening years by Kostelecky and his students and postdocs.
The SME predicts modified speeds for particles, and faster-than-light neutrinos can naturally be described. Nonetheless, Kostelecky said he and other scientists will remain skeptical of the result announced last week until it can be repeated.
"This is obviously an extraordinary claim, which requires extraordinary proof," Kostelecky said. "It will become compelling only if the result can be reproduced by one or more independent experiments."
Options for independent experiments include MINOS at Fermilab in the U.S., at which IU physicists play leading roles, and the T2K experiment in Japan, for which IU College of Arts and Sciences Physics Department Ph.D. graduate Chang Kee Jung, now a neutrino physicist at Stony Brook University in New York, is the international co-spokesperson.
Jung predicted an error in the global positioning system measurements used to record the time from the neutrinos creation to the time they reached the OPERA detector. That was more likely than faster-than-light particles.
"I would be very interested in how they got a 10-nanosecond uncertainty, because from the systematics of GPS and the electronics, I think that's a very hard number to get," he said.
The neutrino speed recorded by OPERA exceeded the speed of light by two parts in a million, with an uncertainly of one-sixth of two parts in a million.
"The OPERA Collaboration has put a lot of effort and care into the measurement, which makes the result very intriguing," said Kostelecky. "At this point, the physics community will be waiting with great interest to see whether the effect can be confirmed."
Originally published Sept. 27, 2011.