Cosmic mystery deepens with discovery of new ultra-high-energy neutrino

August 13, 2015 by Kate Greene, Lawrence Berkeley National Laboratory
An IceCube event display showing the latest ‘most energetic event.’ Each open circle is an un-hit optical module; the filled spheres show hit modules, with the radius indicating the number of detected photons. The colors indicate the relative time (red is first, then orange, yellow, green, and blue), but with the chosen scale, the timing isn’t that useful. Credit: Leif Radel

Evidence of a fourth ultra-high energy neutrino—the highest-energy neutrino yet—has been detected by the South Pole-based IceCube experiment, a project that Berkeley Lab researchers helped build and to which they currently contribute analysis.

The event was found by researchers at Rheinisch-Westfälische Technische Hochschule Aachen University in Germany as part of a new search for astrophysical muon . The researchers' main analysis objective was to confirm previous IceCube measurements of other astrophysical neutrinos. The new ultra-high-energy neutrino was an unexpected bonus.

Scientists have hoped that ultra-high-energy neutrinos could point to sources of ultra-high-energy cosmic rays—supermassive black holes at the centers of galaxies or hypernova star explosions, for instance. But this most-recent neutrino finding, says Berkeley Lab's Spencer Klein, only "deepens the mystery" of cosmic ray origins.

The new neutrino was found thanks to a muon trail observed by an array of 5,160 optical detectors, using electronics designed and built by Berkeley Lab scientists and engineers. Muons are heavy relatives of electrons and are emitted when a type of neutrino called a muon neutrino interacts with an atomic nucleus. The recently detected muon had such a high energy—about 2600 trillion electronvolts—that it could have only been produced by an ultra-high-energy neutrino. The muon track was several kilometers long, too long for IceCube to have captured the entire trace. This means the actual neutrino energy was likely several times higher than was seen in the detector.

Similar to the way that a muon can lead scientists to a neutrino, a neutrino can point to the origin of cosmic rays. Cosmic rays are charged particles that are suspected to come from ultra-high-energy sources outside the galaxy. But because they are charged particles, they arrive at Earth only after following follow chaotic, twisted paths circling around magnetic field lines in space.

Ultra-high-energy neutrinos are believed to come from the same sources as cosmic rays, but differ in that they are neutral, and they therefore travel in straight lines. So, if you catch a neutrino streaking by, the thinking goes, just look in that direction and you can see a cosmic ray source.

But in recent years, pointing instruments in space at neutrinos' suspected sources hasn't revealed obvious source candidates. Indeed, when instruments were aimed at the sky from where this newest neutrino came, no high-energy phenomena were found. Thus, some theorists have devised models that propose ultra-high-energy neutrinos are actually left over from the birth of the universe or that space might not be symmetric in the way physicists once thought.

At the same time, recent analysis of previous IceCube data by Gary Binder, a Nuclear Science Division graduate student who works with Klein, suggests that the more conventional sources such as supermassive black holes are still more likely.

The issue of the origins of ultra-high-energy neutrinos and cosmic rays is far from settled, says Klein, and this new neutrino doesn't yet shed light on the problem. "A lot of people on IceCube, myself included, have been spending a fair amount of time trying to figure out what this means," Klein says. "We just don't know yet."

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3.3 / 5 (6) Aug 13, 2015
Wild speculation ON: Perhaps dark matter is annihilating and causes the ultra high energy neutrino. In all seriousness they have speculated on what might happen if Dark Matter is annihilated. Could this be that signature.
4.4 / 5 (13) Aug 13, 2015
@bhj: No, it can't, this was at least 2.6*10^15 eV, while most DM candidates are thought to contain ~ 10^9 eV of mass energy. So at least a million times too energetic.

The article reference claims: "The ratios are consistent with neutrinos that were produced by conventional acceleration processes—like what is expected in supernova remnants or around super massive black holes—and then traveled long distances. Exotic models, involving new phenomena like neutrino decay or sterile neutrinos are ruled out or constrained." Unless the new observation somehow rejects or severely strain the older result, this is much more likely non-exotic high energy astrophysical phenomena.
5 / 5 (4) Aug 13, 2015
It would be interesting to know to what galaxies these neutrinos point.
4.5 / 5 (2) Aug 13, 2015
I am particularly interested in the movement direction of neutrinos and the entrance angle at the point of capture, but I can't find any relevant sources that have such data. If anyone knows where I may find such info, please post links in the comments box.
4.3 / 5 (18) Aug 13, 2015
can I just briefly say how impressed I am that this thread is actually about the merits of the paper, and not trolls v. others? Can we all continue to just keep adding trolls/cranks to our ignore list and have more threads like this in the future?
2.3 / 5 (6) Aug 13, 2015

I hope you haven't spoke too soon.
5 / 5 (1) Aug 13, 2015
I don't get the bit about how you can tell where they come from 'cause they travel in straight lines so you just look in that direction. Because 'straight lines' means in curved space, yes? no?
5 / 5 (3) Aug 13, 2015
Photons travel curved space the same way as neutrinos, therefore you look at the direction of the neutrinos and will still divine the source even if geometrically it is not actually where you are looking, is my take on that one.
3 / 5 (2) Aug 14, 2015
I wonder if they are trying to detect the origin point in 'space', with time, or 'out of time'?

As each analysis condition and thus each potential search area, is in an entirely different direction or place.

If one looks up Nickolai Kozyrev's work in such connected research (Einstein level of credibility, in his time), they will find him..finding 'out of time' arrivals of energies from stars. Meaning, zero time passed, in the 'arrival' of the energy, vs the origin point.

He would look at the star, plot it's motion with respect to light distance, then calculate where the star is TODAY, even though we can't see it....and there the energetic from the star would appear in his measurements.

He did this, in perfect scientific discipline and record, for years.

I suspect that the same is happening here. That the arrival of the packet is not of linear time. Ie, greater than light speed.

Kozyrev's work has been obscured so that black projects can hold their lead.
2 / 5 (4) Aug 14, 2015
Maybe these are FTL particles whose existence is being systematically denied. That would explain the non finding of its source as 'plain black space' when in reality there IS something there but that 'something' is receding away faster than light due to the linear integration of all the differential ds/dt over the length sufficient to yield a V>c when integrated.....outside the observable part of our universe. It gets here because its dynamic and kinematic drag is not significant due to it being non interacting with normal matter usually., so the normal terminal V -->c thru neg values is circumvented.
I suspect this post will be deleted in order to favor fluff and troll posts. More is the pity for until we wake up.... but then certain of us ARE cognizant,... military scientists who are not paid to give deference to nonsense.
No matter, it took a load of energy to accelerate those particles to their V(init). Maybe we do not really want to know what energy source that was.
Aug 14, 2015
This comment has been removed by a moderator.
Da Schneib
3 / 5 (2) Aug 16, 2015

Maybe these are FTL particles whose existence is being systematically denied. That would explain the non finding of its source as 'plain black space' when in reality there IS something there but that 'something' is receding away faster than light due to the linear integration of all the differential ds/dt over the length sufficient to yield a V>c when integrated
Then how did the neutrino get here?
5 / 5 (1) Aug 17, 2015
Ultra-high-energy neutrinos are believed to come from the same sources as cosmic rays, but differ in that they are neutral, and they therefore travel in straight lines

Due to lack of knowledge and understanding of this subject the following question arises which will probably have been accounted for but still curious what the answer is: does this neutrino really move in a perfect straight line or is its trajectory still slightly curved?
5 / 5 (1) Aug 17, 2015
I'm slightly confused (or more likely too dumb) but I don't understand how they knew where to aim their telescopes without time/distance information. Everything is moving --- how would they know how far, how fast, and in what direction the hypothetical source might have moved?

- greg

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