New experiment finds neutrinos at light speed
March 19, 2012
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 todiscover 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
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