CNGS-neutrinos

The proton beam at CERN that produces the neutrinos detected at ICARUS and OPERA. Credit: CERN

Albert may still be right. An attempt to repeat an experiment that showed a subatomic particle traveling faster than the speed of light suggests that the earlier result may have erred, and that Einstein’s famed special theory of relativity remains intact.

A mostly European collaboration of physicists working on an experiment called ICARUS announced today that they had tracked neutrinos traveling from CERN, the particle physics lab outside Geneva, to the Gran Sasso National Laboratory, in an Italian mountainside. That is the same subterranean, international traverse that neutrinos make in the OPERA experiment. But unlike OPERA, which found last year that neutrinos reached Italy 60 nanoseconds faster than they would traveling at the supposedly unbreakable cosmic speed limit, ICARUS found that the neutrinos made the trip at a velocity indistinguishable from light speed. The details of the ICARUS finding have been posted to the physics preprint server arXiv.org.

"The evidence is beginning to point towards the OPERA result being an artifact of the measurement," CERN research director Sergio Bertolucci said in a prepared statement.

Potential explanations for the OPERA measurement emerged last month, when researchers on the project publicly announced that two issues with GPS synchronization had come to light. Whether those GPS problems alone can explain the 60-nanosecond discrepancy between measurement and theory has not been resolved.

CERN to LNGS

The underground journey neutrinos take across Europe. Credit: CERN

From the beginning, the physicists working on OPERA were careful to note that their measurement was an anomaly, quite possibly one with a mundane explanation. When they announced their confounding findings in September, they refrained from venturing into any interpretations, saying that they wanted other physicists to help scrutinize the data first. “Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements,” Bertolucci said. “This is how science works."