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Neutrino experiment repeat at Cern finds same result | Neutrino experiment repeat at Cern finds same result |
(40 minutes later) | |
The team behind the finding in September that neutrinos may travel faster than light has carried out an improved version of their experiment - and found the same result. | |
If confirmed by other experiments, the find could undermine one of the basic principles of modern physics. | If confirmed by other experiments, the find could undermine one of the basic principles of modern physics. |
Critics of the first report had said that the long bunches of neutrinos used could introduce an error into the test. | Critics of the first report had said that the long bunches of neutrinos used could introduce an error into the test. |
The new work, posted to the Arxiv repository, used much shorter bunches. | The new work, posted to the Arxiv repository, used much shorter bunches. |
It has been submitted to the Journal of High Energy Physics, but has not yet been reviewed by the scientific community. | It has been submitted to the Journal of High Energy Physics, but has not yet been reviewed by the scientific community. |
The experiments have been carried out by the Opera collaboration - short for Oscillation Project with Emulsion-tRacking Apparatus. | The experiments have been carried out by the Opera collaboration - short for Oscillation Project with Emulsion-tRacking Apparatus. |
It hinges on sending bunches of neutrinos created at the Cern facility (actually produced as decays within a long bunch of protons produced at Cern) through 730km of rock to a giant detector at the Gran Sasso laboratory in Italy. | It hinges on sending bunches of neutrinos created at the Cern facility (actually produced as decays within a long bunch of protons produced at Cern) through 730km of rock to a giant detector at the Gran Sasso laboratory in Italy. |
The initial series of experiments, comprising 16,000 separate measurements spread out over three years, found that the neutrinos arrives 60 billionths of a second faster than light would have, travelling unimpeded over the same distance. | The initial series of experiments, comprising 16,000 separate measurements spread out over three years, found that the neutrinos arrives 60 billionths of a second faster than light would have, travelling unimpeded over the same distance. |
The idea that nothing can exceed the speed of light in a vacuum forms a cornerstone in physics - first laid out by James Clerk Maxwell and later incorporated into Albert Einstein's theory of special relativity. | The idea that nothing can exceed the speed of light in a vacuum forms a cornerstone in physics - first laid out by James Clerk Maxwell and later incorporated into Albert Einstein's theory of special relativity. |
Initial analysis of the work by the wider scientific community argued that the relatively long bunches of neutrinos could introduce a significant error into the measurement. | Initial analysis of the work by the wider scientific community argued that the relatively long bunches of neutrinos could introduce a significant error into the measurement. |
Those bunches lasted 10 millionths of a second - 160 times longer than the discrepancy the team initially reported in the neutrinos' travel time. | Those bunches lasted 10 millionths of a second - 160 times longer than the discrepancy the team initially reported in the neutrinos' travel time. |
To address that, scientists at Cern adjusted the way in which the proton beams were produced, resulting in bunches just three billionths of a second long, so the Opera collaboration could repeat the measurements. | To address that, scientists at Cern adjusted the way in which the proton beams were produced, resulting in bunches just three billionths of a second long, so the Opera collaboration could repeat the measurements. |
'Profound implication' | 'Profound implication' |
The first announcement of evidently faster-than-light neutrinos caused a stir world-wide; the Opera collaboration is very aware of its implications if eventually proved correct. | The first announcement of evidently faster-than-light neutrinos caused a stir world-wide; the Opera collaboration is very aware of its implications if eventually proved correct. |
The error in the length of the bunches, however, is just the largest among several potential sources of uncertainty in the measurement that must all now be addressed in turn; these mostly centre on the precise departure and arrival times of the bunches. | |
"A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny," said Fernando Ferroni, president of Italian Institute for Nuclear Physics in a statement. | "A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny," said Fernando Ferroni, president of Italian Institute for Nuclear Physics in a statement. |
"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." | "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." |
Those measurements may be much longer in coming, as only a few facilities worldwide have the detectors needed to catch the notoriously flighty neutrinos - which interact with matter so rarely as to have earned the nickname "ghost particles". | Those measurements may be much longer in coming, as only a few facilities worldwide have the detectors needed to catch the notoriously flighty neutrinos - which interact with matter so rarely as to have earned the nickname "ghost particles". |
Next year, teams working on two other experiments at Gran Sasso experiments - Borexino and Icarus - will begin independent cross-checks of Opera's results. | Next year, teams working on two other experiments at Gran Sasso experiments - Borexino and Icarus - will begin independent cross-checks of Opera's results. |
The US Minos experiment and Japan's T2K experiment will also test the observations. It is likely to be several months before they report back. | The US Minos experiment and Japan's T2K experiment will also test the observations. It is likely to be several months before they report back. |