What is the speed of antineutrino

Measurements of the OPERA experiment show that neutrinos cover the distance from CERN to Gran Sasso at faster than light speed.

Line for OPERA

Geneva (Switzerland) - Scientists of the OPERA experiment published an extraordinarily surprising result today: When measuring the time of flight of neutrinos between the transmitter and receiver, they found that these particles seem to be flying at around twenty-five millionths of the speed of light. Movements faster than light are forbidden according to Einstein's theory of relativity.

So is the theory of relativity wrong and is modern physics shaking? "I would never say that," says Antonio Ereditato, spokesman for the OPERA collaboration, cautiously. The team has received strange measurement results that the researchers cannot explain - and are therefore asking colleagues all over the world to critically review the measurements.

For Opera, neutrinos are generated at the particle accelerators at CERN in Geneva. These fly around 730 kilometers underground to the Gran Sasso laboratory near Rome. There they are detected and actually examined for completely different properties than their speed: The researchers look for neutrino oscillations in which neutrinos change their so-called "family".

"The result comes as a complete surprise," said OPERA spokesman Antonio Ereditato from the University of Bern. "After many months of follow-up, we couldn't find any instrument effect that could explain the result of the measurement." The result, which is given with a high statistical significance, should actually indicate neutrinos that are faster than light.

"We measure the distance and we measure the time - divide the two together and maintain the speed," explains Ereditato, so it is a very simple measurement. The journey takes 2.43 milliseconds - and the neutrinos travel 60 nanoseconds faster than light. The uncertainties of the measurements add up to 10 nanoseconds, a statistical certainty of 6 sigma, as the experts call it. In the opinion of the OPERA researchers, random measurement errors can therefore be ruled out as an explanation. If the theory of relativity is correct, the only possible explanation would be a systematic error - for example, when coupling the times when neutrinos were created to the arrival times in the OPERA detector via the GPS system. However, the OPERA team was unable to find such a mistake despite the most careful analysis. "And now we had to announce our results - we couldn't sweep them under the rug," said Ereditato. The researchers hope for independent confirmation of this result.