CERN: ‘Faster than Speed of Light’ Reconfirmed (Perhaps!)

 

Speed_Of_Light_by_FX_1988

A fiercely debated experiment that appears to show the accepted speed limit of the Universe can be broken has yielded the same results in a re-run, European physicists said. But peer review in the United States said the experiment still did not resolve doubts and the Europeans themselves acknowledged this "was not the end of the story."

“This result comes as a complete surprise,” said OPERA spokesperson, Antonio Ereditato of the University of Bern. “After many months of studies and cross checks we have not found any instrumental effect that could explain the result of the measurement. While OPERA researchers will continue their studies, we are also looking forward to independent measurements to fully assess the nature of this observation.”


“When an experiment finds an apparently unbelievable result and can find no artefact of the measurement to account for it, it’s normal procedure to invite broader scrutiny, and this is exactly what the OPERA collaboration is doing, it’s good scientific practice,” said CERN Research Director Sergio Bertolucci. “If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements.”

In order to perform this study, the OPERA Collaboration teamed up with experts in metrology from CERN and other institutions to perform a series of high precision measurements of the distance between the source and the detector, and of the neutrinos’ time of flight. The distance between the origin of the neutrino beam and OPERA was measured with an uncertainty of 20 cm over the 730 km travel path. The neutrinos’ time of flight was determined with an accuracy of less than 10 nanoseconds by using sophisticated instruments including advanced GPS systems and atomic clocks. The time response of all elements of the CNGS beam line and of the OPERA detector has also been measured with great precision.

"We have established synchronization between CERN and Gran Sasso that gives us nanosecond accuracy, and we’ve measured the distance between the two sites to 20 centimetres,” said Dario Autiero, the CNRS researcher who will give this afternoon’s seminar. “Although our measurements have low systematic uncertainty and high statistical accuracy, and we place great confidence in our results, we’re looking forward to comparing them with those from other experiments."

“The potential impact on science is too large to draw immediate conclusions or attempt physics interpretations. My first reaction is that the neutrino is still surprising us with its mysteries.” said Ereditato. “Today’s seminar is intended to invite scrutiny from the broader particle physics community.”

The OPERA experiment was inaugurated in 2006, with the main goal of studying the rare transformation (oscillation) of muon neutrinos into tau neutrinos. One first such event was observed in 2010, proving the unique ability of the experiment in the detection of the elusive signal of tau neutrinos.

Here's a representative sample of the peer review of the criticism flying around the Web: "One of the things every scientist learns is that the most pernicious, most hard to eliminate errors are systematic errors.  These are errors that exist because of the very setup of one’s experiment.  They can be hard to recognize, and hard to reconcile. Unless what you are measuring is a well-known property which has been measured a bazillion times before.  In those cases a finding of  g= 20 m/s^2 (on earth at sea level), or that Alpha centauri is only 0.4 light years away, or that neutrino’s fly faster than light needs to be adjusted after the fact to fit what literally millions of other scientist have found."

On September 23, the European team issued a massive challenge to fundamental physics by saying they had measured particles called neutrinos which travelled around six kilometres (3.75 miles) per second faster than the velocity of light, determined by Einstein to be the highest speed possible.

The neutrinos had been measured along a 732-kilometre (454-mile) trajectory between the European Centre for Nuclear Research (CERN) in Switzerland and a laboratory in Italy.

The scientists at CERN and the Gran Sasso Laboratory in Italy scrutinised the results of the so-called OPERA experiment for nearly six months before cautiously making the announcement.

In October, responding to criticism that they had been tricked by a statistical quirk, the team decided they would carry out a second series of experiments. This time, the scientists altered the structure of the proton beam, a factor that critics said could have affected the outome. The modification helped the team identify individual particles when they were fired out and when they arrived at their destination.

The new tests "confirm so far the previous results," the Italian Institute for Nuclear Physics (INFN) said in a press release.

"A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny," the INFN's president, Fernando Ferroni, said.

"The experiment OPERA, thanks to a specially adapted CERN beam, has made an important test of consistency of its result. The positive outcome of the test makes us more confident in the result, although a final word can only be said by analogous measurements performed elsewhere in the world".

In France, Jacques Martino, head of the National Institute of Nuclear and Particle Physics at the National Centre of Scientific Research (CNRS), said "the search is not over. There are more checks of systematics currently under discussion, one of them could be a synchronisation of the time reference at CERN and Gran Sasso independently from the GPS (Global Positioning System), using possibly a fibre."

A paper describing the re-run is published on Friday in the open-access Internet science journal, ArXiv.

In the United States, the famous US particle physics laboratory, Fermilab, said the experiment still failed to resolve questions as to whether the flight of the neutrinos had been accurately timed. Just the tiniest error would skew the whole findings.

"OPERA's observation of a similar time delay with a different beam structure only indicates no problem with the batch structure of the beam, it doesn't help to understand whether there is a systematic delay which has been overlooked," said Jenny Thomas, co-spokesman for the Chicago-based lab's own neutrino experiment, MINOS.

MINOS uses a particle beam generated at Fermilab outside Chicago, with a detector at a mine in Minnesota.

The Daily Galaxy via OPERA press release and AFP

Peer Review quote source science20.com

Image credit: with thanks to Speed_Of_Light_by_FX_1988

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