New experiment finds neutrinos at light speed

Posted by Emma Woollacott

As expected, CERN scientists measuring the speed of neutrinos have discovered that the particles aren't traveling faster than light after all.

Last year, CERN scientists were bemused to discover that a neutrino beam being sent to Italy's Grand Sasso laboratory appeared to be arriving sooner than it should, breaking the speed of light. If correct, this would have indicated that Einstein's theory or relativity was wrong.

But using data from the same short, pulsed neutrino beam - but, crucially, an independent timing system - the ICARUS experiment at  Gran Sasso hasn't replicated the OPERA results.

"The evidence is beginning to point towards the OPERA result being an artefact of the measurement, but it's important to be rigorous, and the Gran Sasso experiments, BOREXINO, ICARUS, LVD and OPERA will be making new measurements with pulsed beams from CERN in May to give us the final verdict," says CERN research director Sergio Bertolucci.

"In addition, cross-checks are underway at Gran Sasso to compare the timings of cosmic ray particles between the two experiments, OPERA and LVD. Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements. This is how science works."

The seven neutrinos observed by ICARUS were picked up by the ICARUS Liquid Argon Time Projection Chamber, a new detector which allows an accurate reconstruction of neutrino interactions," says ICARUS spokesperson Carlo Rubbia.

"The fast associated scintillation pulse provides the precise timing of each event, and has been exploited for the neutrino time-of-flight measurement. This technique is now recognized world wide as the most appropriate for future large volume neutrino detectors."