CUORE: Creating the coldest cubic meter in the universe

Yale scientists working on the cryostat of the Cryogenic Underground Observatory for Rare Events (CUORE). 

The experiment is located in a clean room deep underneath the Gran Sasso mountain in Italy to shield the experiment from cosmic rays and other environmental backgrounds. 

Credit: CUORE collaboration

The drive to create the coldest cubic meter in the universe may be centered in Italy, but its ultimate success will depend on instruments developed at Yale University.

An international team of scientists recently set a world record by cooling a copper vessel with a volume of a cubic meter down to a temperature of 6 milliKelvins, or -273.144 degrees Celsius.

It was the first experiment to chill an object so large this close to absolute zero.

The collaboration, called CUORE (Cryogenic Underground Observatory for Rare Events), involves 130 scientists from the United States, Italy, China, Spain, France, and other countries.

It is based at the underground Gran Sasso National Laboratory (LNGS) of the Instituto Nazionale di Fisica Nucleare (INFN), in Italy.

"This is a major technological achievement," said Karsten Heeger, a professor of physics at Yale and director of Yale's Arthur W. Wright Laboratory.

CUORE is part of the new experimental program in neutrinos and dark matter pursued at the Wright Lab.

Yale physicists are building and testing instrumentation that will be used at temperatures of 10mK in the experiment's cryostat, which is the chilled chamber.

Reina Maruyama, an assistant professor of physics, is one of the original proponents for the US involvement in CUORE and is a coordinator of its data analysis

"In collaboration with the University of Wisconsin, we have developed a detector calibration system that will deploy radioactive sources into the coldest region of the cryostat and characterise our detectors," Heeger said.

Once the CUORE experiment is fully operational, it will study important properties of neutrinos, the fundamental, subatomic particles that are created by radioactive decay and do not carry an electrical charge.

Specifically, the experiment will look at a rare process called neutrino-less double-beta decay.

The detection of this process would let researchers demonstrate, for the first time, that neutrinos and anti-neutrinos are the same, thereby offering a possible explanation for the abundance of matter, rather than anti-matter, in the universe.

The experiment uses heat-sensitive detectors that operate in extremely cold temperatures. "It poses a unique challenge," Heeger said.

"We are trying to detect a minuscule amount of heat from nuclear decay, but need to know this very precisely. The detector calibration will tell us if we see the heat from double-beta decay or environmental backgrounds."

Now that the cryostat has reached base temperature, the commissioning and cryogenic testing of the calibration system will take place in the next few months, Heeger said.

More information: crio.mib.infn.it/wigmi/pages/cuore.php

The Ice Cube: Searching for Neutrinos at the South Pole - Video

Scientists like Ignacio Taboada, an assistant professor in the Georgia Tech School of Physics, are using a one cubic kilometer block of ice at the South Pole to help unravel one of the great scientific mysteries of our time.

A 250 TeV neutrino interaction in IceCube. 

At the neutrino interaction point (bottom), a large particle shower is visible, with a muon produced in the interaction leaving up and to the left. 

The direction of the muon indicates the direction of the original neutrino.

Image Credit: NSF

The IceCube Neutrino Observatory at the South Pole is a telescope like no other on Earth.

This giant structure buried deep beneath the Antarctic ice has done what no other telescope or space probe could, it has discovered the first neutrinos from outside our solar system.

IceCube’s discovery has created a whole new frontier for astronomers. One where scientists don’t just observe giant objects from distant galaxies, but the tiny particles that form them.

This discovery may help scientists explain supernovae, black holes, pulsars, active galactic nuclei and other extreme extra-galactic phenomena.

The IceCube Observatory at the Amundsen-Scott South Pole Station, in Antarctica.

Image Credit: Sven Lidstrom, Intensive research

Neutrinos are tiny, near-massless particles created by “cosmic accelerators”.

These are violent astrophysical sources such as exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars.

Neutrinos aren’t rare: our sun creates 65 billion neutrinos every second for every square centimetre of Earth, but neutrinos from outside the solar system are extremely hard to detect; partly because they are so incredibly small, but also because we are swamped with billions upon billions from inside our own solar system.

The IceCube Observatory has found 28 needles in this metaphorical haystack, 28 neutrinos that scientists are convinced are from outside our solar system.

The hot water drill manages to bore deep holes through the Antarctic ice.

Image Credit: NSF

Currently the IceCube can’t tell us the exact origins of the neutrinos but they have speculated on the direction and general area.

According to Science magazine: “the origin of this flux is unknown, the findings are consistent with expectations for a neutrino population with origins outside the solar system.”

The IceCube Observatory was designed for this very purpose. It is a unique structure consisting of 86 strings drilled deep into the Antarctic ice.

Attached to these strings are 5,160 digital optical modules, which are embedded between 1.4 and 2.4km below the Antarctic ice.

Vladimir Papitashvili

"IceCube is a wonderful and unique astrophysical telescope.” said Vladimir Papitashvili, Antarctic astrophysics and geospace science programme director with the National Science Foundation.

“It is deployed deep in the Antarctic ice, but looks over the entire universe."

The IceCube Observatory consists of 86 arrays dug almost two and a half kilometres into the ice. 

Image credit: Nasa-verve, Wikipedia

How it works
Neutrinos carry information about the workings of the most distant phenomena in the universe.

But it’s hard to capture /measure neutrinos because they are near massless, and carry no electrical charge.

Neutrinos are not affected by electromagnetic forces, and pass straight through matter, including the Earth.

They do, however, causes tiny flashes of blue light, called Cherenkov light, when they interact with the ice. It is these tiny blue flashes deep beneath the South Pole that IceCube has been built to monitor.

A Digital Optical Module (DOM) being attached to the final string just before the detector array was switched online 

Image Credit: Peter Rejcek, NSF

Rather than looking into the sky, the IceCube monitor has over five thousand Digital Optical Modules (DOMs).

Each one has a photomultiplier tube (PMT) and a data acquisition computer. A PMT is a vacuum tube that is extremely sensitive to light in the ultraviolet, visible and near-infrared range.

It can multiply the current produced by such light by as much as 100 million times.

Digital Optical Modules are suspended on strings in holes melted into the ice using a hot water drill, at depths ranging from 1,450 to 2,450 metres 

Image Credit: Amble, Wikipedia

Breaking the ice
These DOMs are attached to 86 different strings that have been buried deep beneath the ice.

Scientists used a hot water drill to bore holes with depths ranging from 1,450 to 2,450 metres and suspended the DOMs on the strings beneath the ice.

The photomultiplier tube inside the DOM scans for the Cherenkov effect, and the on-board computer sends any data back to the surface.

According to the National Science Foundation the observation of 28 very high-energy particle events constitutes the first solid evidence for astrophysical neutrinos from cosmic accelerators.

Francis Halzen

"This is the first indication of high-energy neutrinos coming from outside our solar system," says Francis Halzen, principal investigator of IceCube and the Hilldale and Gregory Breit Distinguished Professor of Physics at the University of Wisconsin-Madison.

"It is gratifying to finally see what we have been looking for. This is the dawn of a new age of astronomy."

IceCube Detector under Antarctic ice may have seen first cosmic neutrinos

IceCube, the giant experiment buried beneath the South Pole's ice has recorded the first neutrinos ever detected originating outside our solar system, researchers say.

Neutrinos are produced in our atmosphere but the IceCube experiment -- a cubic kilometer of sensitive detectors sunk into the Antarctic ice -- has seen the first "cosmic neutrinos," they said.

IceCube consists of 86 strings, each with 60 sensitive light detectors strung along it like "fairy lights," sunk deep into the ice.

Rare collisions of neutrinos with the nuclei of atoms in the ice produce a brief flash that the detectors can catch.

With more than 5,000 detectors catching the flashes the direction of the neutrinos' arrival on Earth can be determined, the researchers said.

Neutrinos can be produced in the Earth's atmosphere -- IceCube picks up about 100,000 of that variety a year -- but previous attempts to isolate neutrinos created in far-flung cosmic processes had all failed.

However, in April the IceCube research team reported detecting two neutrinos -- nicknamed Bert and Ernie -- with energy levels high enough to suggest a cosmic rather than atmospheric origin.

The team has now reported 26 more events of similar energy that they expect will also be confirmed as cosmic in origin.

Francis Halzen

Detection is just a first step and "of course, there's much more to do," IceCube principle investigator Francis Halzen told reporters.

"It's after you find them that the work starts; these events are very difficult to analyze."

The study results were presented Wednesday at the IceCube Particle Astrophysics Symposium in Madison, Wis.

The IceCube Lab by Moonlight - Neutrino Watching

The IceCube lab is illuminated by moonlight. 

Scientists are using the world's biggest telescope, buried deep under the South Pole, to try to unravel the mysteries of tiny particles known as neutrinos, hoping to shed light on how the universe was made.

Picture: REUTERS/Emanuel Jacobi/NSF

The Trouble With Neutrinos That Outpaced Einstein’s Theory

The British astrophysicist Arthur S. Eddington once wrote, “No experiment should be believed until it has been confirmed by theory.”

So when a group of physicists going by the acronym Opera announced in September that a batch of the strange subatomic particles known as neutrinos had traveled faster than the speed of light in a 457-mile trip through the earth, the first response among many physicists was to wonder what had gone wrong with the experiment. 

After all, Albert Einstein’s theory of relativity, which proclaimed the speed of light as the cosmic speed limit, is the foundation of modern science and has been shown to work to exquisite precision zillions of times. 

Knock it down and you potentially open the door to all kinds of things, like the ability to go back in time and kill your grandfather.

That, of course, did not stop the rest of us in the physics bleachers from dragging the old guru of space-time by his frizzy coronal hair into the media version of the public square and crowing that, perhaps this time at last, Einstein was finally going to be proved wrong. 

Neutrino jokes proliferated on the Internet, as well as this rousing song by the Corrigan Brothers and Pete Creighton: 

Tooraloo, tooraloo, tooraloo, tooralino,

Is light now slower than a neutrino?

Now it seems that Einstein’s six-month nightmare may be over.

Last week another team of physicists whose apparatus lives right next door to the Opera group — under Gran Sasso mountain in Italy — reported that they had clocked neutrinos, produced in an accelerator at CERN, outside Geneva, racing over the same path to Gran Sasso at the speed of light and not a whit faster. 

Which is exactly how fast scientists had always thought the enigmatic particles, with barely zilch for mass, should go.

The second group, which goes by the acronym Icarus, was led by Carlo Rubbia, a former director of CERN and a Nobel-winning physicist, who called the results “very convincing.”

Physicists swung into line with great sighs of relief.

“The evidence is beginning to point toward the Opera result being an artifact of the measurement,” said CERN’s research director, Sergio Bertolucci.

Cue the famous picture of Einstein sticking out his tongue. As it happened, the Icarus result was announced on March 16, two days after his 133rd birthday — almost in time for the cake.

Adding to the sense of finality was the simple fact — as Eddington might have pointed out — that faster-than-light neutrinos had never been confirmed by theory. Or as John G. Learned, a neutrino physicist at the University of Hawaii, put it in an e-mail, “An interesting result of all this fracas is that no new model I have seen (or heard of from my friends) really is credible to explain the faster-than-light neutrinos.”

During a panel discussion recently at the American Museum of Natural History, Sheldon L. Glashow, a physics professor and Nobel laureate from Boston University, said the best theory he had heard was that the neutrinos had behaved lawfully in Switzerland and speeded up when they crossed the border into Italy.

Eddington’s dictum is not as radical as it might sound. He made it after early measurements of the rate of expansion of the universe made it appear that our planet was older than the cosmos in which it resides — an untenable notion.

“It means that science is not just a book of facts, it is understanding as well,” explained Michael S. Turner, a cosmologist at the University of Chicago, who says the Eddington saying is one of his favourites. 

If a “fact” cannot be understood, fitted into a conceptual framework that we have reason to believe in, or confirmed independently some other way, it risks becoming what journalists like to call a “permanent exclusive” wrong. 

Read more of this article: The Trouble With Neutrinos - NYTimes.com

Missing: Electron antineutrinos and Understanding matter-antimatter imbalance

An international particle physics collaboration has announced its first results toward answering a longstanding question - how the elusive particles called neutrinos can appear to vanish as they travel through space.

The result from the Daya Bay Reactor Neutrino Experiment describes a critical and previously unmeasured quality of neutrinos, and their antiparticles, antineutrinos, that may underlie basic properties of matter and explain why matter predominates over antimatter in the universe.

Embedded under a mountain near the China Guangdong Nuclear Power Group power plant about 55 kilometers from Hong Kong, the Daya Bay experiment used neutrinos emitted by powerful reactors to precisely measure the probability of an electron antineutrino transforming into one of the other neutrino types.

The results, detailed in a paper submitted to the journal Physical Review Letters, reveal that electron neutrinos transform into other neutrino types over a short distance and at a surprisingly high rate.

"Six percent of the electron antineutrinos emitted from the reactor transform over about two kilometers into another flavor of neutrino. Essentially they change identity," explains University of Wisconsin-Madison physics professor Karsten Heeger. Heeger is the U.S. manager for the Daya Bay antineutrino detectors.

Coincident with presentations by other principal investigators in the Daya Bay collaboration, Heeger is describing the results in a talk at the Symposium on Electroweak Nuclear Physics, held at Duke University.

Neutrinos oscillate among three types or "flavors" - electron, muon, and tau - as they travel through space. Two of those oscillations were measured previously, but the transformation of electron neutrinos into other types over this distance (a so called "mixing angle" named theta one-three, written ?13) was unknown before the Daya Bay experiment.

"We expected that there would be such an oscillation, but we did not know what its probability would be," says Heeger.

The Daya Bay experiment counted the number of electron antineutrinos recorded by detectors in two experimental halls near the Daya Bay and Ling Ao reactors and calculated how many would reach the detectors in a more distant hall if there were no oscillation. The number that apparently vanished on the way - due to oscillating into other flavors - gave the value of theta one-three.

After analyzing signals of tens of thousands of electron antineutrinos emitted by the nuclear reactors, the researchers discovered that electron antineutrinos disappeared at a rate of six percent over the two kilometers between the near and far halls, a very short distance for a neutrino.

CERN: OPERA Feb 2012 Update on Neutrinos

The OPERA collaboration has informed its funding agencies and host laboratories that it has identified two possible effects that could have an influence on its neutrino timing measurement. These both require further tests with a short pulsed beam.

If confirmed, one would increase the size of the measured effect, the other would diminish it. The first possible effect concerns an oscillator used to provide the time stamps for GPS synchronizations.

It could have led to an overestimate of the neutrino's time of flight. The second concerns the optical fibre connector that brings the external GPS signal to the OPERA master clock, which may not have been functioning correctly when the measurements were taken.

If this is the case, it could have led to an underestimate of the time of flight of the neutrinos. The potential extent of these two effects is being studied by the OPERA collaboration.

New measurements with short pulsed beams are scheduled for May.

OPERA: Neutrinos may be tachyons

For a few days in September 2011, it was the biggest story in the world. The little-known OPERA experiment in Gran Sasso, Italy, had just made an electrifying claim - that subatomic particles called neutrinos had travelled faster than the speed of light.

Next year, two experiments - MINOS at Fermilab in Batavia, Illinois, and T2K in Japan (pictured) - will be able to test the claim. If it stands up, how should we meld these misbehaving particles with the rest of physics?
One option is via tachyons, hypothetical particles that are born speeding faster than light. It turns out that the speed limit imposed by Einstein's special theory of relativity isn't so much a cap that nothing can exceed as a barrier that nothing can cross.

Tachyons were dreamed up to illustrate this: particles born faster than light pose no problem for special relativity as long as they spend their whole lives in the fast lane.

Are neutrinos tachyons? One way they might be is if the universe is filled with a field that interacts with particles as they fly through it. If photons have more drag in that field than neutrinos do, then neutrinos would naturally outpace the speed of light.

This idea may feel familiar: light travels slower in glass than in a vacuum, for instance. So the universe might be permeated with a sort of diffuse glass.

If neutrinos do turn out to be tachyons, theorists will still have their work cut out. Though they are born speeding, tachyons interfere with another demand of special relativity: that a particle's behaviour be the same no matter where it is facing or how fast it is going.

Meanwhile, there is no shortage of other theories scrabbling to explain this most astonishing of results.

Second Experiment Confirms Faster-Than-Light Neutrinos - Einstein's Theory questioned

A new experiment appears to provide further evidence that neutrinos can travel faster than light, contradicting Einstein's theory of relativity that underpins modern thinking of how the universe works.

Albert Einstein published his theory of relativity in 1905 and asserted that nothing - no matter how small - can travel faster than the speed of light, which is approximately 186,000 miles per second.

The experiment, which is the second of its kind this year, took place at the Gran Sasso laboratory in Italy and used a neutrino beam from CERN in Switzerland 450 miles away.

Scientists at the Italian Institute for Nuclear Physics (INFN) said in a statement that their new tests aimed to exclude one potential systematic effect that might have affected the original measurement.

"A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny," said Fernando Ferroni, president of the INFN.

Scientists were shocked in September when a similar experiment found that neutrinos had travelled faster than light and - in theory - arrived at their destination before they set off.

Reuters reports that physicists involved said they had checked and rechecked anything that could have produced a misreading before announcing what they had found.

In an attempt to rule out any margin for error, the beams sent by CERN in this latest experiment were a few nanoseconds shorter than those sent in the September experiment, with larger gaps of 524 nanoseconds between them, resulting in more accurate timing.

"In this way, compared to the previous measurement, the neutrinos bunches are narrower and more spaced from each other," the scientists said. "This permits to make a more accurate measure of their velocity at the price of a much lower beam intensity."

Although errors can still not be completely ruled out, this evidence does further suggest that Einstein's theory of relativity was incorrect, forcing a major rethinking about how the cosmos works. It may even mean that sending information back in time could be made possible.

CERN Press Release on Neutrino Experiment

Geneva, 23 September 2011. The OPERA experiment, which observes a neutrino beam from CERN 730 km away at Italy’s INFN Gran Sasso Laboratory, will present new results in a seminar at CERN this afternoon at 16:00 CEST.

The seminar will be webcast at http://webcast.cern.ch. Journalists wishing to ask questions may do so via twitter using the hash tag #nuquestions, or via the usual CERN press office channels.

The OPERA result is based on the observation of over 15000 neutrino events measured at Gran Sasso, and appears to indicate that the neutrinos travel at a velocity 20 parts per million above the speed of light, nature’s cosmic speed limit.

Given the potential far-reaching consequences of such a result, independent measurements are needed before the effect can either be refuted or firmly established. This is why the OPERA collaboration has decided to open the result to broader scrutiny. The collaboration’s result is available on the preprint server arxiv.org: http://arxiv.org/abs/1109.4897.

The OPERA measurement is at odds with well-established laws of nature, though science frequently progresses by overthrowing the established paradigms. For this reason, many searches have been made for deviations from Einstein’s theory of relativity, so far not finding any such evidence.

The strong constraints arising from these observations makes an interpretation of the OPERA measurement in terms of modification of Einstein’s theory unlikely, and give further strong reason to seek new independent measurements.

“This result comes as a complete surprise,” said OPERA spokesperson, Antonio Ereditato of the University of Bern. “After many months of studies and cross checks we have not found any instrumental effect that could explain the result of the measurement.  

While OPERA researchers will continue their studies, we are also looking forward to independent measurements to fully assess the nature of this observation.”

“When an experiment finds an apparently unbelievable result and can find no artefact of the measurement to account for it, it’s normal procedure to invite broader scrutiny, and this is exactly what the OPERA collaboration is doing, it’s good scientific practice,” said CERN Research Director Sergio Bertolucci.
 
“If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements.”

In order to perform this study, the OPERA Collaboration teamed up with experts in metrology from CERN and other institutions to perform a series of high precision measurements of the distance between the source and the detector, and of the neutrinos’ time of flight.

The distance between the origin of the neutrino beam and OPERA was measured with an uncertainty of 20 cm over the 730 km travel path. The neutrinos’ time of flight was determined with an accuracy of less than 10 nanoseconds by using sophisticated instruments including advanced GPS systems and atomic clocks.

The time response of all elements of the CNGS beam line and of the OPERA detector has also been measured with great precision.

"We have established synchronization between CERN and Gran Sasso that gives us nanosecond accuracy, and we’ve measured the distance between the two sites to 20 centimetres,” said Dario Autiero, the CNRS researcher who will give this afternoon’s seminar. 

“Although our measurements have low systematic uncertainty and high statistical accuracy, and we place great confidence in our results, we’re looking forward to comparing them with those from other experiments."

“The potential impact on science is too large to draw immediate conclusions or attempt physics interpretations. My first reaction is that the neutrino is still surprising us with its mysteries.” said Ereditato. “Today’s seminar is intended to invite scrutiny from the broader particle physics community.”

The OPERA experiment was inaugurated in 2006, with the main goal of studying the rare transformation (oscillation) of muon neutrinos into tau neutrinos. One first such event was observed in 2010, proving the unique ability of the experiment in the detection of the elusive signal of tau neutrinos.


CERN Press Release

Neutrino particle 'flips to all flavours'

An important breakthrough may be imminent in the study of neutrinos.

The multinational T2K project in Japan says it has seen indications in its data that these elementary particles can flip to any of their three types.

The results are provisional because experiments had to be suspended in the wake of the Tohoku earthquake in March.

But if confirmed, they would open the door to further research on where the matter in the Universe came from.

Specifically, such studies would ask why the cosmos is composed of normal matter rather than its opposite - antimatter - which theorists say must have been created in equal amounts at the Big Bang.

"It's a step on the road," explained Professor Dave Wark, of Imperial College London and the STFC's Rutherford Appleton Laboratory, which leads the UK involvement in T2K.

"We want to address this asymmetry, but first we have to show that the different 'flavours' of neutrinos can spontaneously change into each other - something we call 'neutrino oscillation'. So far, our experiments have been very positive," he told BBC News.

Detecting 'ghosts'

Neutrinos are among the fundamental building blocks of matter. They swarm all about us.

The Sun, for example, releases them in huge quantities when it fuses hydrogen to make helium - the raw nuclear process at its core.

They are, however, very difficult to study because they interact so weakly with normal matter. Hence, their nickname - "ghost particles".

Nonetheless, scientists have been able to discern three flavours - electron neutrinos, muon neutrinos, and tau neutrinos.

Previous research has characterised two forms of oscillations.

The T2K experiment has now seen hints for a third transformation - that of a muon neutrino turning into an electron neutrino.

IceCube Spies Unexplained Pattern Of Cosmic Rays

Photo: courtesy IceCube collaboration

This "skymap," generated in 2009 from data collected by the IceCube Neutrino Observatory, shows the relative intensity of cosmic rays directed toward the Earth's Southern Hemisphere.

Researchers from UW-Madison and elsewhere identified an unusual pattern of cosmic rays, with an excess (warmer colors) detected in one part of the sky and a deficit (cooler colors) in another.


Though still under construction, the IceCube Neutrino Observatory at the South Pole is already delivering scientific results - including an early finding about a phenomenon the telescope was not even designed to study.

IceCube captures signals of notoriously elusive but scientifically fascinating subatomic particles called neutrinos. The telescope focuses on high-energy neutrinos that travel through the Earth, providing information about faraway cosmic events such as supernovas and black holes in the part of space visible from the Northern Hemisphere.

However, one of the challenges of detecting these relatively rare particles is that the telescope is constantly bombarded by other particles, including many generated by cosmic rays interacting with the Earth's atmosphere over the southern half of the sky.

For most IceCube neutrino physicists these particles are simply background noise, but University of Wisconsin-Madison researchers Rasha Abbasi and Paolo Desiati, with collaborator Juan Carlos Diaz-Velez, recognized an opportunity in the cosmic ray data.

"IceCube was not built to look at cosmic rays. Cosmic rays are considered background," Abbasi says. "However, we have billions of events of background downward cosmic rays that ended up being very exciting."

Abbasi saw an unusual pattern when she looked at a "skymap" of the relative intensity of cosmic rays directed toward the Earth's Southern Hemisphere, with an excess of cosmic rays detected in one part of the sky and a deficit in another. A similar lopsidedness, called "anisotropy," has been seen from the Northern Hemisphere by previous experiments, she says, but its source is still a mystery.

"At the beginning, we didn't know what to expect. To see this anisotropy extending to the Southern Hemisphere sky is an additional piece of the puzzle around this enigmatic effect - whether it's due to the magnetic field surrounding us or to the effect of a nearby supernova remnant, we don't know," Abbasi says.