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Muon Neutrino To Electron Neutrino Oscillation Conclusively Shown

Soulskill posted about a year ago | from the stunning-neu-results dept.

Japan 46

New submitter Chris Greenley writes "The T2K long baseline neutrino experiment in Japan has just announced conclusive evidence for electron to muon neutrino oscillation at the 7.5 sigma level. (The level needed for discovery is 5 sigma.) This experiment generates a focused beam of electron neutrinos using an accelerator in the J-PARC facility north of Tokyo which is aimed at the massive Super-Kamiokande detector 295 km (185 miles) away, near the west coast of Japan. 'This T2K observation is the first of its kind in that an explicit appearance of a unique flavor of neutrino at a detection point is unequivocally observed from a different flavor of neutrino at its production point.' This result clears the way for CP-violation neutrino studies which could show that 'regular' neutrinos act differently than their antimatter counterparts, a phenomenon that so far has only been observed in quarks. If neutrino CP-violation is found, it could explain why there is such a large predominance of matter over antimatter in the universe."

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Well, duh (0)

Anonymous Coward | about a year ago | (#44336681)

Isn't it obvious?

Re:Well, duh (2, Informative)

Anonymous Coward | about a year ago | (#44336713)

It's only obvious in SU(5). The currently en-vogue SU(2)+SU(3) lie groups only imply it. But you knew that right?

Re:Well, duh (1)

TechyImmigrant (175943) | about a year ago | (#44336751)

I haven't told them about the other transition they haven't noticed.

Re:Well, duh (1)

Whiteox (919863) | about a year ago | (#44341353)

"If neutrino CP-violation is found, it could explain why there is such a large predominance of matter over antimatter in the universe."

But it probably won't.

Why does it matter? (1)

InPursuitOfTruth (2676955) | about a year ago | (#44336765)

Anti-matter rules!

Re:Why does it matter? (1)

HybridST (894157) | about a year ago | (#44336803)

Anti-matter rules. [wikipedia.org]
FTFY

cp? (-1)

Anonymous Coward | about a year ago | (#44336795)

where can i see the pictures of this cp violation ?

Re:cp? (0)

Anonymous Coward | about a year ago | (#44337561)

Catholic Pedophile? I'm not sure how many of them took pictures...

General implications (4, Interesting)

JoshuaZ (1134087) | about a year ago | (#44336827)

They detected 28 electron neutrino interactions, where they would have expected 5 such events without the oscillation in question. This helps underscore how incredibly hard is it to get neutrinos to show up with anything: even when one is manufacturing millions of them, one is lucky to get a tiny set to then show up in your detector. This is connected to how most neutrino detectors are basically large vats of water or some other liquid, because the most we can generally hope for is that if we put enough mass in the way, some neutrinos will by sheer chance run into things.

This is also relevant to what we expect for stellar neutrino observation. Understanding neutrino oscillation gets us a better idea of what sort of neutrino ratios to expect (as a function of energy levels) in other circumstances. Right now, we can observe a lot of natural neutrinos from the sun. But the only neutrinos we've observed from an identified extra solar location, the 1987A http://en.wikipedia.org/wiki/SN_1987A [wikipedia.org] , which was a very close supernova (so close it could be seen with the naked eye). In fact, in that case, the neutrinos arrived before we saw the light. That's not at all connected to the erroneous claim from a few years ago that neutrinos were going faster than light speed. What is happening here is that most of the light in a supernova is formed in the core, and the core of a star is very dense. So it takes a long time for the light to reach the surface of the star. But from the standpoint of neutrinos even very dense star isn't that much of an issue so they can get to the surface much faster. It is possible that this sort of work will give us better understanding both such neutrinos and what to expect when we do observe them from other close supernova.

Neutrinos are still a major area where there's a lot we don't understand, and this research is going to possibly have major implications for our understanding of these elusive particles.

Re:General implications (1)

buchner.johannes (1139593) | about a year ago | (#44336935)

Still, I think in this century materials and systems will be developed which can detect neutrinos 1000 times better than today. That opens up new possibilities in astronomy (solar neutrinos, AGN, looking past the CMB just to name a few).

Yes, neutrinos start the SN explosion according to current models. However, the timing results for SN 1987a were actually inconclusive, as observatories were not connected to calibrated precision timing systems.

Re:General implications (2, Insightful)

Anonymous Coward | about a year ago | (#44336991)

Still, I think in this century materials and systems will be developed which can detect neutrinos 1000 times better than today. That opens up new possibilities in astronomy (solar neutrinos, AGN, looking past the CMB just to name a few).

It could be that there is no magic material that improves interaction and that we will have to just deal with the fact that most neutrinos will not hit anything, regardless of how the detector is constructed. The only road forward for improved detection then would be to make a larger detector. Although projects like IceCube [wikipedia.org] already have detector volumes over a cubic kilometer.

Re:General implications (4, Interesting)

rgbatduke (1231380) | about a year ago | (#44337049)

Um, how? Using Dark Matter detectors? Look, neutrinos couple to existing, known particles -- leptons, although via other more complex processes e.g. inverse beta decay they can couple to protons in nuclei as well. The response we can detect is in proportion to the density of those particles in a medium that can function as a detector, which in turn is proportional to straight up mass density. The interaction probability is phenomenally low for all of the known particles, so one requires large volumes of material to make ANY kind of detector. There are strict limits on the density of ordinary matter, and even more stringent limits on the density of matter that can conceivably used as a detector

So I'm curious -- given that the ratio between the mass density of water and the mass density of e.g. Tungsten, Uranium, Plutonium is only a single order of magnitude, and a reaction cross section that AFAIK depends solely on the mass density, where exactly are the other two orders of magnitude going to come from from any possible variation in materials?

"Systems", well, perhaps. If we use underground cavities filled with water to look for Cerenkov radiation, or chlorine detectors to look for outgassing Argon, we can always make them 10x bigger and hence increase the detector volume 1000 fold. But this is morally equivalent to building 1000 detectors like we have today and combining the data, and it still leaves us with the same issues if one wishes to determine flavor information and not just raw e.g. neutral current flux. Indeed, to get flavor information we will very likely be limited to building 1000 detectors to get 1000 fold increase in data simply because there are size constraints on detectors that are going to detect and resolve e.g. a muon produced in a charged current interaction.

So sure, we can always scale up our existing technology or minor improvements of it to improve detection rates. But I don't think that materials or systems that improve the scaling of the detection technologies we already have are particularly plausible, based on what I now know. So what did you have in mind (as in, do you know something I don't)? Are there other materials that are likely to have orders of magnitude higher cross section for inverse beta decay, or are you just thinking of building bigger/more detectors?

Not flames, BTW -- an honest question.

rgb

Re:General implications (1)

darenw (74015) | about a year ago | (#44337679)

Not practical anytime soon, but maybe someday, we could create materials with muons in place of electrons. Effectively much smaller atoms. Much denser, many more quarks per cubic cm to catch neutrinos. How to keep it stable instead of being ridiculously radioactive and going poof in a microsecond, and make bulk amounts, I have no idea. Crazy new things will be invented in the coming decades. We can't discount the possibility of some impossible-today new material that can catch neutrinos.

Re:General implications (2, Interesting)

Anonymous Coward | about a year ago | (#44337791)

Muonic atoms have been studied for some time now, and there is no indication of any special way to get stability, neither in theory or in experiment. It would have great potential for use in muon-catalyzed fusion if there was some secret to even marginally longer lifetimes. This is not to say it is impossible, as current theories could be wrong. But expecting that will be a particular likelihood has less motivation than expecting we'll fix the long list of problems with the Alcubierre drive. There is also a chance we may be able to build detectors out of unicorn horns, not a complete impossibility, but it is not something I would take into consideration without any further reasons to think such a path would even appear.

I'm not trying to be harsh, but just illustrate that this seems like grabbing at straws, when there are not even any straws.

Helium sticking problem (1)

amaurea (2900163) | about a year ago | (#44338067)

Doesn't the problem of the muon sticking to the resulting helium nucleus too often pose a more important problem for muon catalyzed fusion than the muon life-time? Would the impossible increase in muon life-time suggested here help muon-catalyzed fusion at all?

Re:Helium sticking problem (1)

Anonymous Coward | about a year ago | (#44338643)

Early work and theory suggested that even with a 100% stable muon, the muon sticking would be too much to make it worth while. Although later experiments gave more optimistic values for the sticking percentage, but still not quite marginally viable even if assuming the rest of the process was 100% efficient. Longer lived muons however would give a lot more options for generating them and could lead to greatly increased efficiency in other parts of the system. There are also several reactions and possibilities that could be explored, but otherwise are of little use now because they require interaction with multiple muons, or could allow the muon to be transfered from one atom to another if given enough time.

Re:General implications (1)

mattr (78516) | about a year ago | (#44340591)

Can any useful deflection (lensing) of neutrinos be accomplished with anything less than a black hole?
I came across articles about stars and the CMB as lensing possibilities.
I am wondering if the Earth itself or a lead lens could have any effect at all.

Re:General implications (0)

Anonymous Coward | about a year ago | (#44342251)

It is possible, but at the moment might not be of much use until we get better detection going. So far I don't think there was been any evidence of point sources from neutrino telescopes, and it would seem near impossible to be on the right side of something like the sun to capture a supernova at the moment it happens. Plus the sun emits its own neutrinos. For the Sun though, the focal length is about 550 AU. The focal point for the Earth on the other hand is about 26 light years away.

Eh ... (0, Insightful)

Anonymous Coward | about a year ago | (#44336843)

If anyone had any doubts that Slashdot, the original formula, was dead, I think the comments (both present and not) here prove it.

Re:Eh ... (1)

Anonymous Coward | about a year ago | (#44337057)

Unfortunate timing considering what thread your comment follows. Although more unfortunate that you added to the mess by thinking your complaints about Slashdot were more important or interesting than the rather nerdy story. So, you're a contributing part of the very problem you complain about.

It would have been easy enough to just link say to the Wikipedia article on neutrino oscillation [wikipedia.org] which discusses other examples of experimental measurements of neutrino oscillations. You could have been more technical and point to how this contributes, along with other experiments, to measuring components of the neutrino mixing matrix [wikipedia.org] which may be useful for post-Standard Model theories. Or you could have just been both bitter and on-topic and complain that the title is backwards, that this was electron neutrino to muon neutrino oscillations, not the other way around as has been previously observed to some degree in atmospheric studies.

Re:Eh ... (1)

Chris Greenley (2990113) | about a year ago | (#44337343)

Sorry about that. I edited the title a couple times and apparently didn't notice the resulting mix up. At least I did state it correctly in the body.

Re:Eh ... (1)

Chris Greenley (2990113) | about a year ago | (#44341231)

Err.. it's right in the title, not in the body, whatever... Freaking words...

Re:Eh ... (0)

Anonymous Coward | about a year ago | (#44337581)

I'm sorry for not mentioning hot grits, Natalie Portman or the GNAA in my first post. My sincerest apologies.

You click first. (0)

Impy the Impiuos Imp (442658) | about a year ago | (#44336865)

CP-violation [wikipedia.org]

I was a little scared to click that link. This is the Intertubes, after all.

Re:You click first. (1)

Trax3001BBS (2368736) | about a year ago | (#44338703)

CP-violation [wikipedia.org]

I was a little scared to click that link. This is the Intertubes, after all.

Yet it's got that one line that explains everything so nicely "or, as the analogy goes, some reactions did not occur as often as their mirror image."

another great discovery! (0)

Anonymous Coward | about a year ago | (#44336875)

nice. one "nothing" transforms into another "nothing". pretty fantastic.
let's just say beta decay breaks energy conservation and be done with it.
at least i can go visit a running nuclear reactor now and marvel at the surrounding (missing) "field"
of 17% that doesn't show up anywhere.
some french philosopher said that the absent of something is something.

Re:another great discovery! (0)

Anonymous Coward | about a year ago | (#44337081)

So you postulate that neutrinos don't exist and the energy and momentum just disappears in a way consistent with emitting a particle... and that despite this disappeared energy and momentum also can reappear elsewhere in a manner consistent with a line of flight from the source and can be modulated via the source, it is still nothing. Sounds like you are the one trying to pile on the properties and abilities to a "nothing", to make a "nothing" act like a "something" instead of accepting the theory that says "something" is done by "something."

what? (0)

marcello_dl (667940) | about a year ago | (#44336881)

No faster than light neutrinos traveling on previously unknown hundreds km long tunnels? Meh to you and your >5 sigmas. :-)

Re:what? (0)

Anonymous Coward | about a year ago | (#44339159)

Denial of the Ghost Particle may be tantamount to anti-semitism. Einstein would roll in his grave; and think of the amendments to physics schoolbooks!

Don't let Anonymous find out... (0)

wbr1 (2538558) | about a year ago | (#44336891)

If neutrino CP-violation is found,

Then the LEA will be sending those sick neutrinos to prison....
FTFY

Speed of light violation implication? (1)

Anonymous Coward | about a year ago | (#44337063)

From the experiments I've seen neutrinos travel at the speed of light, which was found and reported with great relish by physicists wishing to undermine the faster than speed of light experiments from a few years ago.

The problem with this is that while it solves one issue, it opens up another, because only objects without mass are supposed to be able to travel at the speed of light such as photons, but neutrinos have been found to change "flavors" or types. And for them to do so requires that they have mass yet they're able to travel at the speed of light. Which is supposed to be impossible.

Clearly something odd is going on. Any physicists care to comment?

Re:Speed of light violation implication? (1, Informative)

Anonymous Coward | about a year ago | (#44337153)

Neutrinos haven't been found to be traveling at the exact speed of light, only at speeds indistinguishable from the speed of light. The error bars around such measurements are not able to distinguish between a particle traveling exactly at the speed of light and a very light particle with a lot of energy to make it travel almost at that speed.

Lets take the neutrino to have a mass near the upper bound of current estimates of 2 eV, and use for example the neutrinos from the 1987A supernova which had energy of many MeV, and just conservatively estimate that the neutrinos had a relativistic factor of about a million. Their speed would different from the speed of light by one part in a trillion. Even though that supernova happened 160,000 light years away, a one part in a trillion speed difference from the speed of light amounts to only a 5 second delay (assuming the neutrino and light were emitted at the same time, which is probably not true for a supernova).

Alternatively, if we consider that we were able to measure neutrino detection to an accuracy of 1 ns, relative to a concurrent light pulse from the source, a one part in a trillion speed difference would require the sources to be 300 million km away to capture the difference with that 1 ns accuracy.

So in other words, the measurements of speeds being at the speed of light are not inconsistent with the neutrinos having a very small amount of mass given current error bars. For comparison, the faster than light claims had neutrinos going faster than light by 50 parts per million, a much larger difference than parts per trillion, and many detectors are sensitive to neutrinos with energy in the GeV or TeV range or more, where their speed difference from the speed of light would be even smaller.

The whole significance of the original discovery of neutrino oscillation was that it was evidence the neutrinos were not going the speed of light and hence had to have some mass. On going work has not quantified that a lot more since then.

Re:Speed of light violation implication? (1)

Anonymous Coward | about a year ago | (#44337165)

On going work has not quantified that a lot more since then.

On going work has quantified that a lot more, as in we have estimates of the difference in masses and better upper bounds on the mass of neutrinos. The word "not" was not supposed to be there.

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44339353)

Thanks for your posts. Nicely explained.

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44337709)

300 million km away

So... 300 Gm?

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44337743)

Or 0.3 Tm, or 300 trillion mm, etc. If you are familiar enough with the prefixes to use Gm, then you should have no problem understanding what a million km is. In this case though, the point was that the distance is much larger than distances that can be achieved on Earth and much larger than distances in previous neutrino studies that vary from 10-1000 km. For those that don't feel like converting units, even if they are just powers of ten, at least then it is a consistent comparison. For anyone else that can handle powers of ten fine, it is arbitrary.

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44338917)

So... 300 Mkm?

;)

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44339073)

Compound prefixes used to be pretty common, as prefixes larger than mega- were not officially adopted until 1960. You'll see plenty of it in many different papers, or even occasionally on equipment (plenty of equipment labeled in kilomegacycles is still running strong in labs today).

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44337733)

This explanation is insufficient. If neutrinos were indeed massive particles we'd see a wide distribution of their velocities, just like we can observe slow and fast protons, slow and fast electrons, slow and fast everything that moves slower than c. Yet, in 100% of experiments that have been done all neutrinos are propagating through space at the speed close to or exactly equal to c.

The more likely explanation is that Relativity Theory is flawed, just like it is flawed in quantum entanglement, or in QED when you compute Feynman integrals by integrating over all photon speeds. There is already too much evidence against Relativity Theory as it presently is. That's why people are working on quantum loop gravity, superstring theories, stochastic force gravity, etc to fix these problems.

Re:Speed of light violation implication? (4, Informative)

As_I_Please (471684) | about a year ago | (#44338599)

This explanation is insufficient. If neutrinos were indeed massive particles we'd see a wide distribution of their velocities, just like we can observe slow and fast protons, slow and fast electrons, slow and fast everything that moves slower than c. Yet, in 100% of experiments that have been done all neutrinos are propagating through space at the speed close to or exactly equal to c.

The reason for this is the extremely small mass of neutrinoes. The current experimentally-derived upper bounds on their mass is around 1 eV (in contrast, an electron has a mass of 511,000 eV). This means that any process that creates a neutrino will give it enough energy to send it off at ultrarelativistic speeds. Even something simple like neutron decay can impart 1 MeV of kinetic energy to a neutrino, which, as the grandparent calculates, means the neutrino is traveling at 0.999999999999*c. Only chemical reactions would release a small enough amount of energy to have non-relatvistic neutrinos. But, chemical reactions don't release neutrinos.

This is why we only see speed-of-light neutrinos. This is also why it's taken so long to discover that they have mass.

Re:Speed of light violation implication? (3, Interesting)

FrangoAssado (561740) | about a year ago | (#44338701)

This explanation is insufficient. If neutrinos were indeed massive particles we'd see a wide distribution of their velocities, just like we can observe slow and fast protons, slow and fast electrons, slow and fast everything that moves slower than c.

That's completely mistaken. We don't find a wide distribution of neutrino velocities because it takes very little energy to make a neutrino go very close to the speed of light (this happens because neutrinos have *very* little mass). This means that there's a very small probability for a neutrino to have a small velocity relative to anything else -- you just have to sneeze at it (that is, interact with it in almost any way) to send it flying away at close the speed of light. So it's *expected* that you'll never actually see a slow neutrino.

There is already too much evidence against Relativity Theory as it presently is.

That's just bullshit. It's true that General Relativity doesn't fit at all with Quantum Mechanics, but there's *no* compelling evidence at all against Relativity (either General or Special). There's *no* known experiment that gives a conclusive result that's different from what Relativity predicts. People are working on other theories because General Relativity doesn't fit with Quantum Mechanics, not because there's evidence against Relativity.

Re:Speed of light violation implication? (2, Interesting)

Anonymous Coward | about a year ago | (#44338935)

It's true that General Relativity doesn't fit at all with Quantum Mechanics

That is overstating things a bit. For the most part, GR and things like QFT get along just fine, and it helps that space-time in GR is locally pretty flat most of the time. And some work comes from just using them together anyways. There are some obvious conflicts (although some I think are more for idealogical reasons than experimental reasons), but it comes down to specific situations, which is part of the difficulty of testing proposed replacements.

Re:Speed of light violation implication? (0)

Anonymous Coward | about a year ago | (#44338875)

If neutrinos were indeed massive particles we'd see a wide distribution of their velocities, just like we can observe slow and fast protons, slow and fast electrons, slow and fast everything that moves slower than c

But we do see a wide variety of kinetic energies of neutrinos. Different detectors are sensitive to different ranges, and many of them can actually measure the energy of the incoming neutrino. We've observed neutrinos from the MeV to the PeV range, which is over 9 orders of magnitude in variation in kinetic energy. You can find papers on various neutrino spectra, and discussion of theoretical implications, etc., The detection of neutrinos is no longer just a yes-no, simple counting process, but now provides more details like energy and direction.

Unfortunately, detection methods usually have a lower limit to the energy they can detect, which at the lowest end is on the order of 1 MeV. As mentioned above, a 2 eV neutrino with 1 MeV of energy is going about 99.9999999999% the speed of light. Distinguishing speeds like that from the speed of light is not easy, and also comes back to the problem that some detection methods have even higher minimum energy thresholds.

The more likely explanation is that Relativity Theory is flawed,

Except you've yet to provide any example of experimental results actually disagreeing with relativity. Several different experiments have given upper bounds on the neutrino mass ranging from 2 eV down to 0.3 eV (in the latter case, add another two 9s to the percentage of c above for the speed). Other measurements give a lower bound on at least on of the flavors of neutrinos being 0.04 eV. This is all in agreement with it being indistinguishable from c at those energies. This is no different than high energy electron velocities being indistinguishable from c in precision measurements that agree closely with relativity (not to mention the numerous aspects of accelerator design where the velocity can just be assumed to be c for engineering purposes).

That's why people are working on quantum loop gravity, superstring theories, stochastic force gravity, etc to fix these problems.

And none of those theories in general are based on the idea of a massless neutrino. By far most of the results and variations of such work has massive neutrinos. There are plenty trying to find massless neutrino alternatives, but so far they seem to be running into problems of oscillations not being possible (for reasons in addition to the main relativity objection) or disagreeing with measurements already taken. Additionally, because of the high precision of testing already showing experimental agreement with relativity, such theories would have to limit back to relativity in less extreme situations, and you could get stuck with being limited by relativity anyways with the energies being discussed. There may still be a viable massless neutrino theory out there, but I wouldn't hold your breath, or act like it is immediately obvious to an armchair physicist.

Re:Speed of light violation implication? (1)

kermidge (2221646) | 1 year,28 days | (#44357229)

My thanks to you and the other AC's who've left me with a far better almost-understanding of neutrinos than when I started. This is the kind of discussion I relish here. It informs, teases (possibles, speculation, what if, how the hell?), and delights my inner scientist. Now I'm off to refresh my non-understanding of CP-violation, causality, and timeline. Again, thank you.

From https://en.wikipedia.org/wiki/CP_violation [wikipedia.org] and the first section on CP symmetry, there is this gem: "some reactions did not occur as often as their mirror image." The vampire shows up in the mirror only when he's not there?

My head hurts already. But it's kinda fun to try digging this stuff.

Could we build an oscillation over thruster? (0)

Anonymous Coward | about a year ago | (#44338899)

Came here for this. /Left disappointed.

CP violation? (0)

Anonymous Coward | about a year ago | (#44338993)

Call that guy from "How to catch a predator", he's a pro in the subject! I bet he'll find all the CP violations this Muon Mafia has made!

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