Official Word on Superluminal Neutrinos Leaves Warp-Drive Fans a Shred of Hope—Barely

by Edwin Cartlidge on 24 February 2012, 11:31 AM

The CERN particle physics laboratory in Geneva has confirmed Wednesday's report that a loose fiber-optic cable may be behind measurements that seemed to show neutrinos outpacing the speed of light. But the lab also says another glitch could have caused the experiment to underestimate the particles' speed.

In a statement based on an earlier press release from the OPERA collaboration, CERN said two possible "effects" may have influenced the anomalous measurements. One of them, due to a possible faulty connection between the fiber-optic cable bringing the GPS signals to OPERA and the detector's master clock, would have caused the experiment to underestimate the neutrinos' flight time, as described in the original story. The other effect concerns an oscillator, part of OPERA's particle detector that gives its readings time stamps synchronized to GPS signals. Researchers think correcting for an error in this device would actually increase the anomaly in neutrino velocity, making the particles even speedier than the earlier measurements seemed to show.

CERN's statement says OPERA scientists are studying the "potential extent of these two effects" but doesn't indicate which source of error (if either) is likely to outweigh the other. However, Lucia Votano, director of the Gran Sasso laboratory, says the "main suspicion" focuses on the optical-fiber connection. She adds that OPERA researchers deserve credit for "having tenaciously followed this particular evidence via checks completed in the last few days."

The two effects will get a new round of tests in May, when the two labs are scheduled to make velocity measurements with short-pulsed beams designed to give readings much more precise than scientists have achieved so far.

November 18, 2011

Scientists Report Second Sighting of Faster-Than-Light Neutrinos

By DENNIS OVERBYE

Few scientists are betting against Einstein yet, but the phantom neutrinos of Opera are still eluding explanation.

Two months after scientists reported that they had clocked subatomic particles known as neutrinos going faster than the speed of light, to the astonishment and vocal disbelief of most of the world’s physicists, the same group of scientists, known as Opera, said on Friday that it had performed a second experiment that confirmed its first results and eliminated one possible explanation for how the experiment could have gone wrong.

But the group admitted that many questions remain. “This is not the end of the story,” said Antonio Ereditato of the University of Bern in Switzerland, the spokesman for the collaboration, explaining that physicists would not accept the result that neutrinos could go faster than light until other experiments had come up with the same conclusion. “We are convinced, but that is not enough in science,” he said.

Other physicists said they remained skeptical that the universe was about to be overturned.

The speed of light was established as the cosmic speed limit, at least for ordinary matter in ordinary space, in 1905 by Albert Einstein’s theory of relativity (now known as special relativity), foreclosing the possibility of time travel into the past or of timely travel to other stars.

Neutrinos, though ghostly in many regards — they are able to traverse planets and walls of lead like light through a window, and to shape-shift from one of three varieties of the particle to another along the way — are part of the universe, and so there was no reason to expect that Einstein’s stricture should not apply to them as well.

But over the course of the last three years, in experiments designed to investigate this shape shifting, neutrinos produced at CERN, the European Organization for Nuclear Research, and beamed underground to the Gran Sasso National Laboratory in Italy, an underground facility about 450 miles away, arrived about 58 billionths of a second sooner than would a light beam, according to Opera. The group is based at Gran Sasso, which is near L’Aquila; CERN is in Geneva.

When these results were presented to a meeting at CERN in September, after a prairie fire of blog rumors, they were greeted by fierce skepticism. Among the problems with the original experiment, scientists said, was that the neutrinos were produced in bursts 10,000 billionths of a second long — much bigger than the discrepancy in arrival time.

Last month CERN retooled so that the neutrinos could be produced in shorter bursts, only 3 billionths of a second long, making it easier to match neutrinos at Gran Sasso with neutrinos at CERN, and the experiment was briefly repeated. The neutrinos still arrived early, about 62 billionths of a second early, in good agreement with the original result and negating the possibility, the Opera team said, that the duration of the neutrino pulse had anything to do with the results.

The details of both the first and second round of experiments are contained in a paper posted on the Internet at http://arxiv.org/abs/1109.4897 and submitted to the Journal of High Energy Physics. In response to reports that some members of the Opera group had refused to sign a preliminary version of the paper in September, Dr. Ereditato said of the new paper, “They all signed.”

Physicists said the new paper had answered some of the questions about the experiment, but many remain: for example, about how the clocks were synchronized between Geneva and Gran Sasso, and how the distance between them was ascertained. “It does appear that they have done a good job,” said John Learned, a neutrino physicist at the University of Hawaii at Manoa who was not involved in the experiment. But, he added, “If there is a deep systematic error in the calculation of expected time difference, this remains.”

Alvaro de Rujula, a CERN theorist, said there were two interpretations of the experiment. “One is that they have stumbled upon a revolutionary discovery; the other, on which I would place my bet, is that they are still making and not finding the very same error.”

In the meantime, Einstein sleeps peacefully.

Asked if he had seen any interesting theoretical explanations of how neutrinos could violate the speed of light among the papers that have been flooding the internet these past two months, Dr. Ereditato demurred. “That’s not our business,” he said. “A good experimentalist tries to be as cool as possible.”

Dr. Learned and Dr. de Rujula both said there were no convincing theories out there yet. “The theory papers are amusing in that it more and more points out how very much trouble this result will cause, if verified,” Dr. Learned said in an e-mail.

He added, “Fun!”

Source: NYT Space & Cosmos

Tiny Neutrinos May Have Broken Cosmic Speed Limit

Tiny Neutrinos May Have Broken Cosmic Speed Limit
By DENNIS OVERBYE
Published: September 22, 2011

Roll over, Einstein?

The physics world is abuzz with news that a group of European physicists plans to announce Friday that it has clocked a burst of subatomic particles known as neutrinos breaking the cosmic speed limit — the speed of light — that was set by Albert Einstein in 1905.


If true, it is a result that would change the world. But that “if” is enormous.


Even before the European physicists had presented their results — in a paper that appeared on the physics Web site arXiv.org on Thursday night and in a seminar at CERN, the European Center for Nuclear Research, on Friday — a chorus of physicists had risen up on blogs and elsewhere arguing that it was way too soon to give up on Einstein and that there was probably some experimental error. Incredible claims require incredible evidence.

“These guys have done their level best, but before throwing Einstein on the bonfire, you would like to see an independent experiment,” said John Ellis, a CERN theorist who has published work on the speeds of the ghostly particles known as neutrinos.

According to scientists familiar with the paper, the neutrinos raced from a particle accelerator at CERN outside Geneva, where they were created, to a cavern underneath Gran Sasso in Italy, a distance of about 450 miles, about 60 nanoseconds faster than it would take a light beam. That amounts to a speed greater than light by about 0.0025 percent (2.5 parts in a hundred thousand).

Even this small deviation would open up the possibility of time travel and play havoc with longstanding notions of cause and effect. Einstein himself — the author of modern physics, whose theory of relativity established the speed of light as the ultimate limit — said that if you could send a message faster than light, “You could send a telegram to the past.”

Alvaro de Rujula, a theorist at CERN, called the claim “flabbergasting.”

“If it is true, then we truly haven’t understood anything about anything,” he said, adding: “It looks too big to be true. The correct attitude is to ask oneself what went wrong.”

The group that is reporting the results is known as Opera, for Oscillation Project with Emulsion-Tracking Apparatus. Antonio Ereditato, the physicist at the University of Bern who leads the group, agreed with Dr. de Rujula and others who expressed shock. He told the BBC that Opera — after much internal discussion — had decided to put its results out there in order to get them scrutinized.

“My dream would be that another, independent experiment finds the same thing,” Dr. Ereditato told the BBC. “Then I would be relieved.”

Neutrinos are among the weirdest denizens of the weird quantum subatomic world. Once thought to be massless and to travel at the speed of light, they can sail through walls and planets like wind through a screen door. Moreover, they come in three varieties and can morph from one form to another as they travel along, an effect that the Opera experiment was designed to detect by comparing 10-microsecond pulses of protons on one end with pulses of neutrinos at the other. Dr. de Rujula pointed out, however, that it was impossible to identify which protons gave birth to which neutrino, leading to statistical uncertainties.

Dr. Ellis noted that a similar experiment was reported by a collaboration known as Minos in 2007 on neutrinos created at Fermilab in Illinois and beamed through the Earth to the Soudan Mine in Minnesota. That group found, although with less precision, that the neutrino speeds were consistent with the speed of light.

Measurements of neutrinos emitted from a supernova in the Large Magellanic Cloud in 1987, moreover, suggested that their speeds differed from light by less than one part in a billion.

John Learned, a neutrino astronomer at the University of Hawaii, said that if the results of the Opera researchers turned out to be true, it could be the first hint that neutrinos can take a shortcut through space, through extra dimensions. Joe Lykken of Fermilab said, “Special relativity only holds in flat space, so if there is a warped fifth dimension, it is possible that on other slices of it, the speed of light is different.”

But it is too soon for such mind-bending speculation. The Opera results will generate a rush of experiments aimed at confirming or repudiating it, according to Dr. Learned. “This is revolutionary and will require convincing replication,” he said.


This article has been revised to reflect the following correction:

Correction: September 22, 2011

A previous version of this article misspelled Alvaro de Rujula's last name.

A version of this article appeared in print on September 23, 2011, on page A8 of the New York edition with the headline: Tiny Neutrinos May Have Broken Cosmic Speed Limit.


Source: NYT Sciense