Monday, October 31, 2011

The way it is done...neutrino experiment

"European Physicists Will Race Neutrinos Again, Trying to Reproduce Faster-Than-Light Results"


Rebecca Boyle

October 31st, 2011


The physicists who claimed to see neutrinos moving faster than light are moving quickly to replicate their experiment, hoping to substantiate their results before submitting them for publication. Since announcing their bizarre, seemingly impossible findings last month, physicists around the world have offered a few possible explanations. But perhaps the best test will be a retest.

The OPERA experiment sends a beam of neutrinos from CERN in Geneva, through the mountains to Italy’s Gran Sasso National Laboratory. The point is to look for flip-flops in neutrino flavor, which requires precisely measuring and averaging the chargeless particles’ arrival and departure times. It was in this routine timing that a team led by Antonio Ereditato found particles apparently moving faster than light. They were arriving at Gran Sasso about 60 nanoseconds earlier than the time it would take light to travel the same distance.

This violates the known laws of physics, but the OPERA collaborators saw it happen so frequently that it couldn’t be a fluke; they released their findings to the greater scientific community, hoping for some insight. Several other physicists have since proposed new theoretical explanations, including the possibility that the clocks on the GPS satellites used for the precise arrival-departure timing do not themselves account for relativistic motion. Other researchers have said the OPERA team must be committing some unknown and repeated systematic error. This is part of the team’s motivation for rechecking their findings, according to BBC News. CERN research leader Sergio Bertolucci said the team is sending a different time pattern, which will allow OPERA to repeat the measurement with different data. This could remove some of the possible systematic errors, he said.

Bertolucci said the experimenters would not “fool around,” given the physics-shattering implications of the results.

The new measurements will fire protons in super-short bursts (one or two nanoseconds), then wait about 500 nanoseconds before firing another burst. The short burst will allow for precise measurements and efficient neutrino monitoring, Bertolucci told BBC. Originally, the protons were fired in a long beam lasting a comparatively long 10 microseconds. This new beam run will end in November, when CERN has to switch the type of particles it is accelerating. Then the team will re-check its calculations and submit their findings for publication, BBC says.

“They actually planned to make the results public in 2015, but they traveled faster than light and came out last month,” says Associate Editor Paul.

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