Fermilab experiment sees neutrinos change over 500 miles

August 7, 2015
A candidate electron neutrino interaction seen in the NOvA far detector on March 23, 2015. The upper panel shows the top view, looking down into the detector; the bottom panel shows the side view. Each golden box shows a cell of the detector in which particles from the interaction were spotted. The longer of the two tracks in each view is identified as a high-energy electron, telling us that this is likely an electron neutrino interaction. The shorter track is most likely a proton. Credit: NOvA

Scientists on the NOvA experiment saw their first evidence of oscillating neutrinos, confirming that the extraordinary detector built for the project not only functions as planned but is also making great progress toward its goal of a major leap in our understanding of these ghostly particles.

NOvA is on a quest to learn more about the abundant yet mysterious particles called , which flit through ordinary matter as though it weren't there. The first NOvA results, released this week at the American Physical Society's Division of Particles and Fields conference in Ann Arbor, Michigan, verify that the experiment's massive particle detector—50 feet tall, 50 feet wide and 200 feet long—is sitting in the sweet spot and detecting neutrinos fired from 500 miles away. Scientists have sorted through millions of cosmic ray strikes and zeroed in on neutrino interactions.

"People are ecstatic to see our first observation of neutrino oscillations," said NOvA co-spokesperson Peter Shanahan of the U.S. Department of Energy's Fermi National Accelerator Laboratory. "For all the people who worked over the course of a decade on the designing, building, commissioning and operating this experiment, it's beyond gratifying."

Researchers have collected data aggressively since February 2014, recording neutrino interactions in the 14,000-ton far detector in Ash River, Minnesota, while construction was still under way. This allowed the collaboration to gather data while testing systems before starting operations with the complete detector in November 2014, shortly after the experiment was completed on time and under budget. NOvA construction and operations are supported by the DOE Office of Science.

The neutrino beam generated at Fermilab passes through an underground near detector, which measures the beam's neutrino composition before it leaves the Fermilab site. The particles then travel more than 500 miles straight through the Earth, no tunnel required, oscillating (or changing types) along the way. About once per second, Fermilab's accelerator sends trillions of neutrinos to Minnesota, but the elusive neutrinos interact so rarely that only a few will register at the far detector.

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See what the NOvA detector sees in this animation created with real data. This video shows the precision of the far detector, spotting neutrino interactions amidst the cosmic ray noise. Credit: Fermilab

When a neutrino bumps into an atom in the NOvA detector, it releases a signature trail of particles and light depending on which type it is: an electron, muon or . The beam originating at Fermilab is made almost entirely of one type—muon neutrinos—and scientists can measure how many of those muon neutrinos disappear over their journey and reappear as electron neutrinos.

If oscillations did not occur, experimenters predicted they would see 201 muon neutrinos arrive at the NOvA far detector in the data collected; instead, they saw a mere 33, proof that the muon neutrinos were disappearing as they transformed into the two other flavors. Similarly, if oscillations did not occur, scientists expected to see only one electron neutrino appearance (due to background interactions). But the collaboration saw six such events, evidence that some of the missing had turned into electron neutrinos.

Similar long-distance experiments such as T2K in Japan and MINOS at Fermilab have seen these muon neutrino to electron before. NOvA, which will take data for at least six years, is seeing nearly equivalent results in a shorter time frame, something that bodes well for the experiment's ambitious goal of measuring neutrino properties that have eluded other experiments so far.

"One of the reasons we've made such excellent progress is the impressive Fermilab neutrino beam and accelerator team," said NOvA co-spokesperson Mark Messier of Indiana University. "Having a beam of that power running so efficiently gives us a real competitive edge and allows us to gather data quickly."

Fermilab's flagship accelerator recently set a high-energy neutrino beam world record when it reached 521 kilowatts, and the laboratory is working on improving the even further for projects such as NOvA and the upcoming Deep Underground Neutrino Experiment. Researchers expect to reach 700 kilowatts early next calendar year, accumulating a slew of neutrino interactions and tripling the amount of data recorded by year's end.

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Go behind the scenes of the creation of the NOvA far detector in this time-lapse video showing how one of the biggest experiments ever designed was built. Credit: Fermi National Accelerator Laboratory

Neutrinos are the most abundant massive particle in the universe but are still poorly understood. While researchers know that neutrinos come in three types, they don't know which is the heaviest and which is the lightest. Figuring out this ordering—one of the goals of the NOvA experiment—would be a great litmus test for theories about how the neutrino gets its mass. While the famed Higgs boson helps explain how some particles obtain their masses, scientists don't know yet how it is connected to neutrinos, if at all. The measurement of the neutrino mass hierarchy is also crucial information for neutrino experiments trying to see if the neutrino is its own antiparticle.

Like T2K, NOvA can also run in antineutrino mode, opening a window to see whether neutrinos and antineutrinos are fundamentally different. An asymmetry early in the universe's history could have tipped the cosmic balance in favor of matter, making the world we see today possible. Soon, scientists will be able to combine the neutrino results obtained by T2K, MINOS and NOvA, yielding more precise answers about scientists' most pressing neutrino questions.

A graphic representation of one of the first neutrino interactions captured at the NOvA far detector in northern Minnesota. The dotted red line represents the neutrino beam, generated at Fermilab in Illinois and sent through 500 miles of earth to the far detector. The image on the left is a simplified 3-D view of the detector, the top right view shows the interaction from the top of the detector, and the bottom right view shows the interaction from the side of the detector. Credit: Fermilab

"The rapid success of the NOvA team demonstrates a commitment and talent for taking on complex projects to answer the biggest questions in particle physics," said Fermilab Director Nigel Lockyer. "We're glad that the detectors are functioning beautifully and providing quality data that will expand our understanding of the subatomic realm."

The NOvA collaboration comprises 210 scientists and engineers from 39 institutions in the United States, Brazil, the Czech Republic, Greece, India, Russia and the United Kingdom.

Explore further: World record: Most powerful high-energy particle beam for a neutrino experiment ever generated

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BikeToAustralia
5 / 5 (3) Aug 07, 2015
How does "the most abundant massive particle in the universe" "flit through ordinary matter as though it weren't there"? I imagined tiny little particles simply not hitting anything, not the case. What about if they do not have a magnetic field somhow, then they would not... create a wake unless there was a direct hit?

I realize there is much that is not known, but someone knowing more than I and willing to enlighten me (and the rest of us) of this burden of complete ignorance, that person would be appreciated.
shavera
5 / 5 (9) Aug 07, 2015
Bike: When particles "interact" they have to exchange something to talk to each other. The matter you're used to is charged electrically (or made up of electrically charged stuff). So when that matter interacts, they exchange photons back and forth and that "communicates" the force from one to another.

But neutrinos are truly electrically neutral. So they cannot use photons to "talk" to normal matter. What they can use are the "weak bosons" W and Z particles.

The trouble is that W and Z particles weigh as much as an entire lithium or beryllium atom (an isotope thereof). That's huge. So it's very very rare for quantum mechanics to take this path along the way.

Thus, since the neutrinos find it so hard to "talk" to anyone along their paths, they tend to just keep on going.
shavera
5 / 5 (9) Aug 07, 2015
Remember too that our normal everyday experience of "stuff" as being "solid" and "impermeable" doesn't apply to particles. That impermeability is a result of these particles "talking" to each other. There's no reason that these particles can't "pass through" each other. It's only on our bigger macroscopic scales that things behave like our common sense would suggest.

(Also, I've purposefully neglected at least one other way that particles *can* talk to each other, because it's just not relevant in this specific question)
AGreatWhopper
1 / 5 (3) Aug 07, 2015
15 minutes after I read the first "supraluminal" neutrino study I said, "They didn't take into account flavor oscillations". I'm no genius so I have to wonder why it has taken years for such an obvious point to be investigated. Why was that not the professionals' first thought as well?

I guess it didn't fit the "point of the day" funding model that CERN employs.
viko_mx
2.4 / 5 (5) Aug 07, 2015
Neutrinos - elusive propagating vibrations of structure of vacuum of space?
mytwocts
5 / 5 (2) Aug 07, 2015
"experimenters predicted they would see 201 muon neutrinos arrive at the NOvA far detector in the data collected; instead, they saw a mere 33, proof that the muon neutrinos were disappearing as they transformed into the two other flavors. Similarly, if oscillations did not occur, scientists expected to see only one electron neutrino appearance (due to background interactions). But the collaboration saw six such events, evidence that some of the missing muon neutrinos had turned into electron neutrinos"
So they expected 201 but saw only 39 neutrino's. If I believe the phys.org newsflash a 162 neutrino's are still missing. Were these converted in tau neutrino's or is there something wrong here?
shavera
5 / 5 (6) Aug 07, 2015
AGW: They very well took flavor oscillations into account. That was mostly what the experiment was designed to do.

The issue was that a fiber optic cable wasn't screwed on tightly enough. This caused a small delay in some signal propagation that threw off the timing of the measurement apparatus.

------

Viko: No.

----

2cts: These experiments are usually tuned to one neutrino flavour or another, generally electron. The reason they don't see the remaining neutrinos is because the flavour doesn't match the design setup.

How they get it to match, I don't know. But that's the idea at least.
TechnoCreed
5 / 5 (3) Aug 07, 2015
@viko_mx
Neutrinos - elusive propagating vibrations of structure of vacuum of space?
I do not understand why shavira disapproved of your wording. I am generally in agreement with his comments. I do not think that your sentence is a perfect description of neutrinos but I do not see how using your very own word to partly say the same thing as QFT could be wrong. According to Quantum Field Theory, field quantas are both particles and waves (or vibrations). I would also say that a field is a structure of space.
viko_mx
1 / 5 (3) Aug 08, 2015
Why do you think that quantum theory gives a precise description of reality in order to comply with it? It is only an attempt to do so, which has gained popularity due to the great opportunities for bold speculation, which gives this theory. Works with statistical methods which exclude the possibility of an exact description of the behavior of matter particles and their energetic interactions. This reflects the fact that we have no access to fundamental processes supporting the order in our physical reality and can see only little part of the hole picture.
mytwocts
5 / 5 (1) Aug 08, 2015

2cts: These experiments are usually tuned to one neutrino flavour or another, generally electron. The reason they don't see the remaining neutrinos is because the flavour doesn't match the design setup.

The result is a positive identification of 6 conversions to electron neutrino's.
What I am missing is (a statement on) the other 162 neutrino's. How many electron neutrino events are expected if a fraction 168/211 of incoming mu neutrino's changed into e neutrino's?Only 6 ? Note: the detect ion probability of mu and e will be different, tau I assume to be zero.
mytwocts
5 / 5 (4) Aug 08, 2015
quantum theory ... is only an attempt ... which has gained popularity due to the great opportunities for bold speculation ...

You are short selling QM severely. I can give you a bookshelf of reasons why QM "has gained popularity". I can also give you a military arsenal of lasers and atomic bombs, or a whole multibillion dollar semiconductor industry.
You do not seem to know what you are talking about.
mytwocts
5 / 5 (3) Aug 08, 2015
@viko_mx
Neutrinos - elusive propagating vibrations of structure of vacuum of space?
I do not understand why shavira disapproved of your wording.

It is word salad..
A neutrino is not a vacuum fluctuation.
And I have no idea what the "vacuum of space" can mean.
viko_mx
1 / 5 (3) Aug 08, 2015
Lets start from "a" and "b".
Space is geometric consept. In our physical world it has three dimensions. Vacuum that fills this three dimensional space is the actual physical medium in which propagate electromagnetic waves and constituent particles of matter. It has certain physical properties that dictate the behavior of elementary particles and their energetic interactions.
That is the main reason why the theory of relativity for example have nothing to do with physical reality. Its mathematical apparatus work with the space as geometric objects with infinite elasticity instead with vacuum of space which is real physical medium with certain physical propertais and limitations.
mytwocts
5 / 5 (2) Aug 08, 2015
If there is a medium then a) I would not call it the vacuum, since that refers to its ground state and b) it would have to be relativistically covariant. I would rather call it a unified field. The presence of a neutrino would then be a higher energy state of this UF.
mytwocts
5 / 5 (3) Aug 08, 2015
the theory of relativity ... have nothing to do with physical reality.

If Lorentz transformations are just geometry
how e.g. do you explain the energy dependence of muon life time?
https://en.wikipe..._sources
docile
Aug 08, 2015
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docile
Aug 08, 2015
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swordsman
not rated yet Aug 08, 2015
When a neutrino is split apart, an electron and a proton are produced plus some radiating energy. This would lead to the conclusion that a neutrino may simply be a compressed hydrogen atom. As such, the size would be much smaller, and the radiating frequencies produced during a high-energy reaction would also be much higher. Seems to fit.
jeffensley
1 / 5 (1) Aug 08, 2015
Do neutrinos have any interest in interacting with each other? If so, is it possible that they are the elusive dark matter or does dark matter behavior in opposition to the matter that we are familiar as opposed to just neutrally? Also, if we could find a "substance" that interacts/captures neutrinos efficiently, this might be a really good means of communication, locally and universally.
docile
Aug 08, 2015
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docile
Aug 08, 2015
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docile
Aug 08, 2015
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bluehigh
5 / 5 (1) Aug 09, 2015
When a neutrino (!) is split apart, an electron and a proton are produced ...
- swordsman

Huh? Cool new physics? No, sadly just a typo or too much medication.

A NEUTRON decays into an electron and a proton plus a bit of something.
docile
Aug 09, 2015
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docile
Aug 09, 2015
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docile
Aug 09, 2015
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DonGateley
not rated yet Aug 10, 2015
Why did we need this experiment to "discover" what we already knew from the spectrum of solar neutrinos? Expensive verification that seems hardly seems necessary or adds to what was known before it.
jsdarkdestruction
4 / 5 (4) Aug 10, 2015
Don, how much of the article did you read?
"NOvA, which will take data for at least six years, is seeing nearly equivalent results in a shorter time frame, something that bodes well for the experiment's ambitious goal of measuring neutrino properties that have eluded other experiments so far"
A more detailed description can be found in the last paragraphs as well.
docile
Aug 10, 2015
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docile
Aug 10, 2015
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DonGateley
not rated yet Aug 10, 2015
Thank you, docile, for the kind of answer I hoped my impertinent question would provoke. :-)
bluehigh
not rated yet Aug 10, 2015
Perhaps Neutrinos could be renamed to avoid confusion with Neutrons. The feeble minded seem to have difficulty in the rush to gush.

Hmmm ... a better name for Neutrinos (not Neutrons) ... How about Hydrinos?
Oh that's right they have different properties. Or do they?

What's with the flavours. How much do properties of an entity need to alter before it's not the same entity. For example, just because a proton has one quark with a differing property, we don't say a neutron is a flavoured proton. Or vice versa.
docile
Aug 10, 2015
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