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Indication of Neutrino Transformation Observed
AmiMoJo writes "A Japanese research group says it has observed for the first time an indication that a type of neutrino can change into another type. The group generated a large amount of neutrinos at the Japan Proton Accelerator Research Complex, or J-PARC, in the prefecture's Tokai Village, and aimed them at the Super-Kamiokande observatory in Gifu Prefecture about 300 kilometers away, to look for neutrino oscillation. As a result, the group observed that muon neutrinos can change into electron neutrinos."
How do they know they were the same neutrinos they launched out?
Rocket Surgeon.
what's the connection with fukashima?
-- Flame me and I will happily flame you back. Bring it!
observed for the first time an indication that a type of neutrino can change into another type
Oh, really?
How can I believe you when you tell me what I don't want to hear?
Getting those little tags on em is a bitch!
It's a particular oscillation that they've observed for the first time.
Assuming this result is correct then this result implies that there is a CP symmetry violation between the neutrino and anti-neutrino.
Previously to this result this particular mixing term could have been zero and if it was zero then CP symmetry would have been preserved.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
How did they tell? cause the mutated nuetrinos dont have ears.
Could you say that again, but with more words this time?
Hmm, don't think so. This mixing can be nonzero (i.e. what they observed) and the CP violating phase could still be zero, in fact the T2K analysis assumes \delta_{CP} = 0 as there is currently no information on the CP violating phase. T2K's article
I thought neutrinos almost never interact with more regular matter because they're too small to collide with atoms, how can they get their statistics?
Wait, what are we talking about again?
Yes, you're right. I had thought that non-zero theta13 was sufficient.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
I can try. But as someone else has replied what I wrote is not actually correct.
Because there are three different neutrinos, we need three different numbers to describe how they can oscillate (change) between flavours.
What oscillate means is that if you start with a beam of pure electron neutrinos and then, at some later time measure the type of the neutrinos you will find that some of them are now muon or tau neutrinos.
Two of those numbers were known to be non-zero. This result suggests that the third number is also non-zero.
I had thought that all three numbers being non-zero was sufficient to show that neutrinos violate CP - but that is incorrect.
CP violation is when you replace every particle with its antiparticle (C) and look at the resulting system in a mirror (P). CP violation means that you can tell the difference between the two systems
CP has been observed and is important because it's conjectured that the fact that the universe has more matter than anti-matter is a feature of CP violation.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
A friend of mine does this. She spends weeks at a time at the bottom of an abandoned mineshaft, with a swimming pool full of scintillator, working 14 hour days
Adventure. Heh. Excitement. Heh. A Jedi craves not these things.
THE NEUTRINOS HAVE MUTATED
It's a particular oscillation that they've observed for the first time.
No it is not. SuperK first observed this type back in 1998 but the results were not conclusive (they saw muon neutrino "disappearing" but not what they converted into). Since then MINOS and MiniBooNE have observed this exact type of neutrino oscillation (around 2003 IIRC - but they have multiple papers published now) and the OPERA experiment has even got some evidence of muon to tau oscillation. (Look them all up in Wikipedia or Google).
Assuming this result is correct then this result implies that there is a CP symmetry violation
No it does not. For T2K (the experiment they are talking about) to see a matter/antimatter asymmetry (CP violation) one of the mixing angles, theta_13 must be large and they need a LOT more data.
Well, since it isn't subject to magnetic or electrical forces, it basically has to slam into the nucleus (extremely unbelievably unlikely) or into an electron (unbelievably massively completely entirely extremely ... well about the same chance that anyone in the world likes a justin bieber song).
Essentially, it needs to get close enough to another particle - by coincidence - for the weak force to start having a decent effect on them.
I am a physicist working on the experiment, for more information on this story please check out my blog post http://bit.ly/NuBlogT2KNuE1
CP violation was discovered in the 1960's or 1970's. CP violating Kaon decays have been studied to death. Are you trying to say something more profound?
Dragging out Yang-Mills, doesn't this just mean that neutrino masses are different? Same way that K_short and K_long masses differ? (Ex-particles guy -- been close to two decades since work in the field -- so maybe I'm missing something.)
I think CP violation in the neutrino sector might have different physical implications than in kaons. It would certainly be dependent on a different set of mixing angles.
So, if one neutrino can change into another type without any energy gain/release, then it must be only one type.
Assuming this result is correct then this result implies that there is a CP symmetry violation between the neutrino and anti-neutrino.
The oscillation T2K just observed is not related to CP violation. It's simpler than that. There are three types of neutrinos. If they can change types, then there are three ways they could do so (draw yourself a triangle with each neutrino at a vertex, the sides are how they could change into each other).
Solar neutrinos start of as electron neutrinos and change on their way to earth (that's one of the sides). muon neutrinos are seen to change to tau neutrinos in Super-K's atmospheric neutrino signal and the MINOS accelerator experiment (that's the second side). This result is the first clear measurement of the third side, electron to muon changes. MINOS has made a similar but much messier measurement, T2K's is much cleaner.
CP violation is in the theory, but it's a second-order effect. That effect is multiplied by the size of this new electron/muon effect, so we need to measure this first, then we can look for "delta", the CP-violating phase.
(and yes, I Am a Neutrino Physicist - worked for many years on Super-K, now work on MINOS and Nova).
If I understand correctly, very much simplified it's more like counting the number of red cars going into a big tunnel, then counting where they exit and notice that there are now less red cars but more green cars coming out?
Not necessarily. They could be different neutrinos, caused by atoms in the way absorbing some neutrinos and emitting others. I am not sure but I suspect that is what GP was getting at. Rather than evidence of neutrinos actually changing from one type to another, it seems just as likely (more likely?) that intervening matter performed a conversion.
So here's the thing about skepticism.
You start out with an excellent question -- how do we know (or rather, quantify our confidence that) it was the neutrinos changing in-flight, rather than something else, like them being absorbed and re-emitted by intervening matter?
Then, rather than treat this like a question to which you do not know the answer, and try to find out, you instead decide that it's "just as likely (more likely?)" that your interpretation is correct.
Skepticism is based around the idea of asking honest questions, and then looking for the answer.
Skepticism is not based around asking a rhetorical question (or just phrasing it as a statement), not bothering to find an answer, and assuming that your ability to ask a question means the conclusions of the research are now in doubt.
Skepticism, and science, are not about just asking questions. They're about seeking knowledge. They are never about letting ignorance serve as evidence.
I hope this help clears up a common confusion regarding question asking and skepticism.
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a radioactive neutrino.
But the particular information that I was asking about, that is, the cause of neutrino oscillations (which you would know if you had actually been paying attention rather than being a snotty smartass), is not, to the best of my knowledge, to be found there.
I paid attention, it's why I googled you up "why" for you. Did you pay attention? The answer to your question was right in there! You may have had to click a link in the text to get to the fuller explanation, sorry! But the answer I already gave you is: It's a natural consequence of neutrinos having (different) masses, and quantum mechanics. In QM, the neutrino isn't a classical particle of one well-defined type sailing along, that "mysteriously" decides to become a different particle in the middle. It's a QM-wave-particle-thing described by probabilistic equations. Until it interacts with something and the waveform collapses, it really isn't any one of the possible outcomes (if there are more than one).
Which theory says there would be, if the different neutrino flavors have mass. That's why you always hear about neutrino mass and oscillation at the same time. Because way back in the late 50s, they figured out that if you assumed unequal masses for the neutrino flavors (and so non-zero for at least two of the three), then the neutrino wave functions for each flavor would include the possibility of being a different flavor. So seeing evidence for neutrino oscillation is evidence for a successful prediction from which we can infer that neutrinos have mass.
None of it is "proven" with a sufficiently large evidence pool like you say, but within the theory that is making these so-far so-good predictions, there is a well-defined explanation for why this is happening.
What you seem to have missed in the paper you linked was that this mechanism is not one of the issues "still under discussion". They're talking about details of the predictions, the specific probabilities and characteristics, and how that meshes with experiment. Like why does a known-bad assumption for calculating the probabilities result in correct predictions? And then they proceed to answer, by factoring in the phase of the wave packet first, making the bad assumption unnecessary. Those answers will probably continue to be debated, but the point is "Why are these things even oscillating in the first place" wasn't up for grabs.
Unless you want to know the underlying mechanism behind wave functions, superposition of states and other QM weirdness. Then of course nobody knows the answer to "Why this crazy shit?", but at the same time the "That's Just Too Weird So It Can't Be Right!" ship sailed a long time ago. Particles can't be thought of as little spheres in space with well-defined identities so sometimes they seem to spontaneously switch; deal with it.
So there's your answer (again). If you need a more detailed answer than that, why precisely QM and the Standard Model say this will happen, take a class, read a (text)book, at least a website, what-fucking-ever. Just stop acting like being able to ask a question means your alternative is just as likely, without doing any of those things. Or acting like getting called out for doing that is the same as being called out just for asking a question.
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