quantumaniac:

Neutrino evidence against “faster-than-light” claim

Neutrinos do not go faster than light, according to new measurements made by an experiment called ICARUS at the Gran Sasso Laboratory using a new measuring technique, called a liquid argon time projection chamber and working independently from the OPERA scientists who had made the tentative but extremely controversial claim about “faster-than-light” particles. Particles that travel faster than light would unravel Albert Einstein’s 1905 theory of special relativity, a cornerstone of modern physics.

Their findings “indicate the neutrinos do not exceed the speed of light,” the European Centre for Nuclear Research (CERN) said, ading that there may have been technical hitches that had skewed the initial measurements, something that skeptics of the findings said they had always suspected.

The controversy began last September, when CERN’s so-called OPERA team cautiously announced that sub-atomic particles called neutrinos had travelled some six kilometres (nearly four ) per second faster than the velocity of light, described by Einstein as the maximum speed in the cosmos.

The neutrinos were timed at their departure from CERN’s giant underground lab near Geneva and again, after travelling 732 km (454 miles) through the Earth’s crust, at their arrival at the Gran Sasso Laboratory in Italy.

To complete the trip, the neutrinos should have taken 0.0024 seconds. Instead, the particles were recorded as hitting the detectors in Italy 0.00000006 seconds sooner than expected.Knowing their findings would create a global controversy, the OPERA team urged other physicists to carry out their own checks to corroborate or refute what had been seen.

“ICARUS measures the neutrino’s velocity to be no faster than the speed of light,” said Carlo Rubbia, a Nobel winner and spokesperson for the ICARUS project..”Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny and inviting independent measurements. This is how science works,” said CERN Research Director Sergio Bertolucci, who added that further verifications were being made, including new experiments with particle beams in May, “to give us the final verdict.”

In February, CERN said that the OPERA team were verifying a cable connection and a timing instrument called an oscillator that may have flawed measurements of the neutrinos’ flight time.Strengthening this scenario, Bertolucci said on Friday “the evidence is beginning to point towards the OPERA result being an artifact of the measurement.”

Oh, yeah. Moving faster than the speed of light has been the hot topic in the news and OPERA has been the key player. In case you didn’t know, the experiment unleashed some particles at CERN, close to Geneva. It wasn’t the production that caused the buzz, it was the revelation they arrived at the Gran Sasso Laboratory in Italy around 60 nanoseconds sooner than they should have. Sooner than the speed of light allows!

Since the announcement, the physics world has been on fire, producing more than 80 papers – each with their own opinion. While some tried to explain the effect, others discredited it. The overpowering concensus was the OPERA team simply must have forgotten one critical element. On October 14, 2011, Ronald van Elburg at the University of Groningen in the Netherlands put forth his own statement – one that provides a persuasive point that he may have found the error in the calculations.

To get a clearer picture, the distance the neutrinos traveled is straightforward. They began in CERN and were measured via global positioning systems. However, the Gran Sasso Laboratory is located beneath the Earth under a kilometre-high mountain. Regardless, the OPERA team took this into account and provided an accurate distance measurement of 730 km to within tolerances of 20 cm. The neutrino flight time is then measured by using clocks at the opposing ends, with the team knowing exactly when the particles left and when they landed.

But were the clocks perfectly synchronized?

Keeping time is again the domain of the GPS satellites which each broadcasting a highly accurate time signal from orbit some 20,000km overhead. But is it possible the team overlooked the amount of time it took for the satellite signals to return to Earth? In his statement, van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

(via Special relativity may answer faster-than-light neutrino mystery)