An improved re-run of the experiment that appeared to show faster-than-light travel was possible has produced the same result. In September, CERN's OPERA experiment found that neutrinos were traveling to the Italian measuring station at San Grasso about 20 parts per million faster than the speed of light.
Since then, the team has rechecked many aspects of its analysis, taking other scientists' suggestions into account
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One of the most important tests, now completed, was to repeat the measurement with very short beam pulses from CERN. This allowed the extraction time of the protons that ultimately lead to the neutrino beam, to be measured more precisely.
The beam sent from CERN consisted of pulses three nanoseconds long separated by up to 524 nanoseconds. Some 20 clean neutrino events were subsequently measured at Gran Sasso, and precisely associated with the pulse leaving CERN - confirming that it wasn't inaccurate timing that was to blame.
"The new measurements do not change the initial conclusion," says CERN.
"Nevertheless, the observed anomaly in the neutrinos' time of flight from CERN to Gran Sasso still needs further scrutiny and independent measurement before it can be refuted or confirmed."
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