Faster-than-light neutrinos? ------------------------------------------------------------------------------ The news broke on 23 September 2011, making banner headlines around the world: the international OPERA experiment claimed to have observed faster-than-light neutrinos. This was in complete contradiction with Einstein’s theory of special relativity, which predicts that no particle OPERA experiment: the scientific with mass can exceed a speed of 299,792,458 meters per second. However, some neutrinos produced by CERN’s accelerators in Geneva approach is not in dispute and detected 730 kilometers away at the Gran Sasso underground ------------------------------------------------------------------------- laboratory in Italy were found to arrive 60 nanoseconds early. The The point of view of Jacques Martino, Director of the CNRS National announcement was met with scepticism among physicists. New tests Institute of Nuclear and Particle Physics. were carried out, and results from other experiments at Gran Sasso ‘With his theory of special relativity, Einstein showed that nothing can travel faster were found to contradict those of OPERA. Meanwhile, the OPERA than the speed of light in a vacuum, which is why the researchers of the OPERA teams identified possible sources of error in their measuring chain. experiment were dumbfounded when they saw that their results appeared to call Measurements carried out in May 2012 finally settled the debate. the theory into question. Their initial reaction was to double-check all the equipment in the facility, as well as the various stages in their analysis: they could not find any source of error. They then called upon the scientific community to think of potential snags. The rest is history: a faulty connection probably skewed the measurements: this was finally confirmed in 2012. What must be remembered from this experience is the quality of the scientific approach implemented by the OPERA team, who acted with irreproachable integrity. There was no ethical misconduct but rather an experimental error, which is more frequent than generally believed.’ When the speed of light depends on its direction When light goes back and forth, it travels at the same speed in both directions. However, in the presence of an electromagnetic field, theory predicts a tiny variation in its speed depending on the direction it is moving in. Now, CNRS researchers have provided experimental evidence of this in a gas. By enhancing the precision of their experiment, they should be able to test certain speculative theories that call into question the invariance of the speed of light, even in a vacuum. Physical Review Letters May 2011 At the INFN Gran Sasso Laboratory in Italy, the OPERA experiment observes a beam of neutrinos sent from CERN, 730 kilometers away. Antineutrinos change flavors First results from the international Double Chooz experiment were revealed at the LowNu11 conference, held in South Korea in November 2011. The physicists detected the oscillation of antineutrinos produced at the Chooz nuclear power plant, in France: the detector, located 1,000 meters from the reactor, showed that a number of electron antineutrinos had clearly switched to tau and muon flavors. The Double Chooz physicists were thus able to estimate the value of a key neutron oscillation parameter known as the 013 mixing angle. This important Installing the photomultipliers that line the walls of the tank result has been given significant backing by two other experiments. in the Double Chooz detector. LowNu11 conference, Seoul (South Korea) 9-11 November 2011 39 2011 A year at CNRS
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