Environment Clean Generations: neutrino

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Neutrino Observatory - The Second-Largest Human Structure Ever Built

Forty different universities and institutions from across Europe are partnering on a project to build a neutrino observatory under the Mediterranean sea that will be the second-largest structure ever built by humans, after the Great Wall of China.

The KM3NeT telescope will have a volume of "several" cubic kilometres -- hence the odd name, which purportedly stands for "kilometre-cubed neutrino telescope". It will comprise of a number of towers -- each taller than the 830-metre Burj Khalifa in Dubai -- which will be filled with spheres containing photomultiplier tubes, which will record neutrinos passing through.

Neutrinos are notoriously tricksy little particles, formed in certain types of radioactive decay. They get their name because they carry no electrical charge, but that property also means that they can pass through matter virtually unimpeded, making them difficult to spot. Whereas an electron passing through a 3-centimetre thick sheet of metal will lose significant amounts of energy, a neutrino of the same energy would need something like a light-year's worth of heavy metal to lose the same amount.

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Peter Fisher, a particle physicist at MIT, explained to Popsci: "Anytime you detect a particle, what you're always doing is having the particle interact with some kind of matter, whether it's water, steel, air or ice. The less the particle interacts, the more material you need for it to interact in."

KM3NeT uses the ocean instead. Hundreds of metres of seawater act as a shield, blocking interference from particles generated in our atmosphere, and allow the photomultipliers to capture the bright blue flash caused when a neutrino hits the nucleus of an atom and produces a charged particle known as a muon.
Giorgio Riccobene, a staff researcher at the Italian National Institute for Nuclear Physics, said: "This is the light we look for to reconstruct the trajectory of the muon," Riccobene said. "So, in this sense, it is an underwater telescope. The water allows us to see the reaction more clearly."

The structure is still in the planning phases, and funding is proving problematic given the current state of European finances and politics, but if all goes well then construction could begin as early as 2012.

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Neutrino Experiment Repeat at Cern Finds Same Result

The team which found that neutrinos may travel faster than light has carried out an improved version of their experiment - and confirmed the result.

If confirmed by other experiments, the find could undermine one of the basic principles of modern physics.

Critics of the first report in September had said that the long bunches of neutrinos (tiny particles) used could introduce an error into the test.

The new work used much shorter bunches.

It has been posted to the Arxiv repository and 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 (T)racking 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 (454 miles) of rock to a giant detector at the INFN-Gran Sasso laboratory in Italy.

The initial series of experiments, comprising 15,000 separate measurements spread out over three years, found that the neutrinos arrived 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.

Timing is everything

Initial analysis of the work by the wider scientific community argued that the relatively long-lasting 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.
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.
When the Opera team ran the improved experiment 20 times, they found almost exactly the same result.

"This is reinforcing the previous finding and ruling out some possible systematic errors which could have in principle been affecting it," said Antonio Ereditato of the Opera collaboration.

"We didn't think they were, and now we have the proof," he told BBC News. "This is reassuring that it's not the end of the story."

The first announcement of evidently faster-than-light neutrinos caused a stir worldwide; 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, which must all now be addressed in turn; these mostly centre on the precise departure and arrival times of the bunches.

"So far no arguments have been put forward that rule out our effect," Dr Ereditato said.
"This additional test we made is confirming our original finding, but still we have to be very prudent, still we have to look forward to independent confirmation. But this is a positive result."
That confirmation 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.
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.
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Neutrino Explains Matter In Universe

Super-Kamiokande Built in an abandoned mine, the "Super-K" neutrino detector surrounds 50,000 gallons of super pure water with 11,200 photomultiplier tubes. To give an idea of the scale, that object in the distance is two men in a rubber raft.

Japan’s “T2K,” one of our favorite neutrino experimentsmight have just cracked the mystery of why matter triumphed over antimatter after the Big Bang (they should have canceled each other out). The international experiment’s data from earlier this year--before its science was interrupted by the earthquake in March--indicates that muon neutrinos can transform into electron neutrinos.

A primer on neutrinos and why we should care about them: Neutrinos are one of the fundamental building blocks of matter, though they interact very weakly with normal matter (innumerable neutrinos kicked out by the sun pass straight through the earth at any moment, rarely pausing to interact with the planet). They come in three flavors: muon neutrinos, electron neutrinos, and and tau neutrinos. And for the aforementioned reason they are very hard to detect.

Nonetheless, via detectors like T2K (for Tokai-to-Kamioka, as these are the origin and terminus of the nearly 200-mile experiment) we are able to detect and study neutrinos every now and again. T2K fires a beam of muon neutrinos straight through the ground from Tokai on the east coast to the Super-Kamiokande detector 183 miles away. And recently at Super-K, some of the neutrinos detected were electron neutrinos, indicating that they has had shifted mid-flight.

We already knew about two different oscillations (that’s a change from one flavor of neutrino to another) but we’ve never this new, third oscillation: a muon turning into an electron neutrino.

This is significant, because it means that normal neutrinos could have different oscillation characteristics than their antiparticle counterparts (antineutrinos). It’s an example of what physicists term a CP violation, and it could explain why, when all of our models show that the Big Bang should’ve created equal parts matter and antimatter (which would annihilate each other instantly), an excess of matter clearly survived to make up the universe.

That’s big news, but nothing is yet certain. Repairs are underway at T2K’s accelerator, and the experiment will begin churning out data to corroborate (or disprove) the finding later this year.