Slashdot Mirror
Chameleon-Like Behavior of Neutrino Confirmed
Anonymous Apcoheur writes "Scientists from CERN and INFN of the OPERA Collaboration have announced the first direct observation of a muon neutrino turning into a tau neutrino. 'The OPERA result follows seven years of preparation and over three years of beam provided by CERN. During that time, billions of billions of muon-neutrinos have been sent from CERN to Gran Sasso, taking just 2.4 milliseconds to make the trip. The rarity of neutrino oscillation, coupled with the fact that neutrinos interact very weakly with matter, makes this kind of experiment extremely subtle to conduct. ... While closing a chapter on understanding the nature of neutrinos, the observation of neutrino oscillations is strong evidence for new physics. The Standard Model of fundamental particles posits no mass for the neutrino. For them to be able to oscillate, however, they must have mass.'"
Nobody every buys the Standard Model. If you have the money you get the Luxury Model. Otherwise, most folks just aim for the middle and get the Sports model.
This issue is a bit more complicated than you think.
Reading TFS made me very excited about the potential fundamental developments in physics. Except I don't know a thing about physics, so I'm really not sure what I'm excited about. All these words like muon, tau, and neutrino have little place in my everyday life, but they sound so interesting!
This is what the Average American must feel like when they hear stories about Web x.0 laden with the latest buzzwords on CNN. I can finally relate!
I don't see how changing from one thing into another is "chameleon-like behavior". I have never heard of a chameleon turning into a skink, or anything else for that matter
Climate Progress - Hell and High Water
You'd need a pretty complex theory to get non-mass oscillations to match all the data we got over the past 12 years, which is very compatible with a three-state, mass-driven oscillation scenario. Besides, you'd have to explain more than what the current "new standard model" (the SM with added neutrino masses) does if you want your theory to be accepted. If two theories explain the same data equally well, the simplest is more likely.
The Standard Model of fundamental particles posits no mass for the neutrino. For them to be able to oscillate, however, they must have mass.
Unless oscillation is the fundamental thing and mass is just a sometimes effect of oscillation... but then IANAP.
Moderating "-1, Disagree" is simple censorship. Have the guts to post your opinion.
How could something have mass and so weakly interact with normal matter? My understanding is that most neutrinos pass through the earth unmolested.
(insert obligatory Catholic priest joke here).
I's thought that neutrinos being massless made this possible.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
If two theories explain the same data equally well, the simplest is more likely./quote?
Make that "more preferred". In general we don't know anything about likelihood.
The thing about Occam's Razor is that it filters out "special pleading" type arguments. If you want your pet in the show, you've got to provide motivation for including it.
Sheesh, evil *and* a jerk. -- Jade
That would be pretty amazing as it would violate the Special Theory of Relativity, one of the most tested theories of all time. The problem is, according to Special Relativity, massless particles move at the speed of light, and time does not advance for them. (If you could build a massless clock, its hands would never move.) Oscillations require a time scale. There is a time period of oscillation, or rather the probabilities of being found in a specific state (mu vs. tau, for instance) oscillate with time. Since time stands still for massless particles, this can't happen.
If I can be modded down for being a troll, can I be modded up for being an orc, or a balrog?
God did it.
So that's why fat people live shorter lives! Time really just moves faster for them, because they have more mass!
That's the way I've always understood the mass/oscillation connection too. But then I thought... wait... don't photons oscillate too? They're just coherent oscillations of the EM field; oscillating back and forth between electric and transverse magnetic in free space. If there's something different about neutrino oscillation which makes it necessary for the neutrino to travel at sublight, what is it specifically?
Does that fact that light is polarizable, has known frequencies of oscillation, and no mass (but has momentum), throw a wrench into all this claim that you need mass to oscillate? Probably not on these forums, but it still makes me pause to think about it.
I wouldn't consider the mad hatter mad. Just reality impaired. He sure can make a mean cup of tea.
We've been observing only a third of neutrinos from the sun, and the speculation was that the rest were oscilliating into others not being detected, and that would be possible if neutrinos had mass, and that means one or the other symmetries in the standard model needs to be tweaked, and so on.
Get it? No, I don't get it either, but I'm no physicists.
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
If two theories explain the same data equally well, the simplest is more likely.
Is that really the case? That seems like it's a very hominid-centric assumption. I can't think of any counter examples but it seems very naïve to assume that the nature of the Universe would be simple...? Though, perhaps my understanding is limited.
Well it's VERY difficult to detect relativistic effects at human walking speed but they are still there. So you could create a whole stack of data that supports Newtonian physics over Relativity on that basis, but Relativity, though more complex is a more accurate description of the Universe.
When something doesn't fit your model, more experimentation and experience is needed, and most importantly you may need to do DIFFERENT experiments to determine whether a simpler or more complex theory is more accurate.
These posts express my own personal views, not those of my employer
All you wise guys think this is funny, but what if it turns out to be true? Huh?!
Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
The point is that, if two different theories have the exact same predictions, they are for all intents and purposes the same theory, and describe the same universe. If that is the case, why would you spend more time teaching and learning the more complex one, when a simple explanation is enough and (by definition, since they have the same predictions) you can't tell which one is correct?
Of course, if the new theory offers a good explanation to current data, but has a different prediction than the standard model in other, still-non-tested scenarios, the theory is more interesting. You can test it at the new scenario, and you'll be able to tell them apart. This is why* we study, for example, supersymmetry and extra dimensions theories: they behave just like the standard model where we have tested it, but can be different in other cases such as the LHC.
* = of course there are other motivations to develop the theories, but they are taken seriously because they are compatible with the SM and are testable. A theory whose predictions were exactly the same as the SM for every case wouldn't be worth studying, simply because you'd never be able to see if it is right.
No it is not more likely. That’s a common misconception. It is only the one you should pursuit first. Actual facts make things more likely. Not simplicity. Simplification is a artifact injected by humans, because they prefer it for efficiency. (What is commonly calley “laziness”)
Any sufficiently advanced intelligence is indistinguishable from stupidity.
That's the way I've always understood the mass/oscillation connection too. But then I thought... wait... don't photons oscillate too? They're just coherent oscillations of the EM field; oscillating back and forth between electric and transverse magnetic in free space. If there's something different about neutrino oscillation which makes it necessary for the neutrino to travel at sublight, what is it specifically?
The situation you describe with the EM field is an example of wave-particle duality. Light can behave like both a wave and a particle, but it doesn't make sense to analyze it both ways at the same time. As a wave, it does manifest itself as oscillating electric and magnetic fields and as a particle, it manifests itself as a photon, which doesn't change into a different type of particle. (There's no such thing as an "electric photon" and a "magnetic photon".)
Neutrinos, too, are described quantum mechanically by wavefunctions, and these wavefunctions have frequencies associated with them, related to the energy of the particle. But these have nothing to do with the oscillation frequencies described here, in which a neutrino of one flavor (eg. mu) can change into a different flavor (eg. tau). Quantum mechanically speaking, we say the mass eigenstates of the neutrino (states of definite mass) don't coincide with the weak eigenstates (states of definite flavor: i.e. e, mu, or tau). Without mass, there would be no distinct mass eigenstates at all, and so mixing of the weak eigenstates would not occur as the neutrino propagates through free space.
If I can be modded down for being a troll, can I be modded up for being an orc, or a balrog?
Thanks. I just found some equations that appear to reinforce what you said.
Since the oscillation frequency is proportional to the difference of the squared masses of the mass eigenstates, perhaps it's more accurate to say that neutrino flavor oscillation implies the existence of several mass eigenstates which aren't identical to flavor eigenstates. Since two mass eigenstates would need different eigenvalues in order to be distinguishable, this means at least one mass eigenvalue has to be nonzero. There's probably some sort of "superselection rule" which prevents particles from oscillating between massless and massive eigenstates, so both mass eigenstates have to be non-zero. Cool.
Offhand, this doesn't seem like a very robust result - we're only talking about a single observation, after all. Does the equipment allow them to determine the source of the observed tau neutrino? How can they be sure that it came from the muon neutrino stream from CERN rather than being random background?
There's also no mention of a control, e.g., another tau neutrino detector close to the same muon neutrino source. Even if there was, is a single detection versus no detections statistically significant?
I don't know of any superselection-rule -- it's possible, in theory, for the electron neutrino to have zero mass but the muon neutrino to have nonzero mass.
But then you'd have to explain why one flavor was massive while the other was massless, which has never happened before. Since there's lots of precedent for three flavors with different nonzero masses, people just figure that the neutrinos are the same way.
I don't know of any superselection-rule -- it's possible, in theory, for the electron neutrino to have zero mass but the muon neutrino to have nonzero mass.
You can't have oscillations between massless and massive states. Remember, SR says that time stands still for massless particles. If you look at the equations for neutrino oscillations, for example here, you'll see there are expressions involving both the mass squared (for the time evolution of the wavefunction), and mass difference squared, for the mixing amplitudes. So, for quantum mechanical mixing between states, you need both non-zero masses and non-zero mass differences. There may be other, weird mixing theories which don't require mass differences, but they would be quite exotic. On the other hand, mixing of particles with zero masses would violate SR, which would be highly surprising!
If I can be modded down for being a troll, can I be modded up for being an orc, or a balrog?
1. If an electron neutrino can spontaneously transform to a tau neutrino with higher mass, where exactly does the required energy come from? Alternatively, when a tau neutrino transforms to an electron neutrino, where does the extra energy disappear?
2. If neutrinos have mass, then they are restricted to speeds below c. If they are accelerated to near c, then according to the relativistic energy-momentum equations they should have colossal mass, not miniscule (just like electrons, for example). Is there any evidence of observing neutrinos with huge energies?
The Wiki article about neutrino oscillation paints the picture that the oscillation is a pseudo-illusionary quantum mechanical effect, and therefore questions like the two above are meaningless. Smells more like handwavium to me.
Could a real physicist push back the veil of shadows one bit? Pretty please? =)
Capitalization is the difference between "Helping your uncle jack off a horse" and "Helping your uncle Jack off a horse"
No. All flavour eigenstates MUST be massive: they are superpositions of the three mass eigenstates, one of which can have zero mass. Calling the three mass eigenstates n1, n2 and n3; and the three flavour eigenstates ne, nm and nt, we'd have:
ne=Ue1*n1+Ue2*n2+Ue3*n3
nm=Um1*n1+Um2*n2+Um3*n3
nt=Ut1*n1+Ut2*n2+Ut3*n3
So, if any of n1, n2 or n3 has a non-zero mass (and at least two of them MUST have non-zero masses, since we know two different and non-zero mass differences), all three flavour eigenstates have non-zero masses.
Also, remember that the limit for the neutrino mass is at about 1eV, while it's hard to have neutrinos travelling with energies under 10^6 eV. In other words, the gamma factor is huge, and they're always ultrarelativistic, travelling practically at "c".
Another point is that the mass differences are really, really small; of the order of 0.01 eV. This is ridiculously small; so small that the uncertainty principle makes it possible for one state to "tunnel" to the other.
I really can't go any deeper than that without resorting to quantuim field theory. I can only say that standard QM is not compatible with relativity: Schrödinger's equation comes from the classical Hamiltonian, for example. To take special relativity into account, you need a different set of equations (Dirac's), which use the relativistic Hamiltonian. In this particular case, the result is the same using Dirac, Schrödinger or the full QFT, but the three-line Schrödinger solution becomes a full-page Dirac calculation, or ten pages of QFT. In this particular case, unfortunately, the best I can do is say "trust me, it works; you'll see it when you get more background".
The time-dependent Schrödinger's equation doesn't apply for massless particles. It was never intended to. It isn't relativistic. Try to apply a simple boost and you'll see it's not Poincaré invariant. The main point is that you get the same probabilities if you use a relativistic theory, but you need A LOT of work to get there.
Oscillations work and happen in QFT, which is Poincaré-invariant and assumes special relativity. I can't find any references in a quick search, but I've done all the (quite painful) calculations a long time ago to make sure it works. It's one of those cases where the added complexity of relativistic quantum field theory doesn't change the results from a simple Schrödinger solution.
This reminds me of the /. post a few days ago about those who are ignorant of science and proud to be so. This is how I think some of them might perceive this situation:
Last week, a Normal would have been told by Those Who Do Science that a neutrino has no mass, and that is the end of the matter. A non-physicist has nothing to contribute to the discussion. Persistent disagreement amounts to sheer ignorance, so keep quiet.
But now, it would appear that either neutrinos have mass or the Standard Model is wrong. Science has revealed its own ignorance. Everyone who was wrong last week is right this week. But the message to the Normals remains the same: it doesn't matter that we were wrong last week; eventually, We Who Do Science get it right. You still have nothing to say. Keep quiet.
The Normals perceive the above and conclude that it's hypocrisy. Hence, they can ignore science and be proud that they are smart enough to avoid hypocritical know-it-all's.
BTW: Yes, this is post if Offtopic, but it's not Flamebait or Troll. I'm not agreeing with this POV; I'm passing on my perception of it. And how else can one discuss the interrelationship between topics without being regarded as Offtopic in regards to one post or the another?
I wish I had an answer of how to fix the above problem. Eliminating arrogant PhD's would be helpful, but that would leave all of the arrogant Normals -- and the rest of us aren't free from shocking amounts of arrogance at times, either. We could use another Sagan to highlight that math+science is a process that anyone can join in on once the ground-rules are mastered. However, it would me imperative that the next spokesperson not be hostile to religion -- the Normals are hypersensitive to this issue, and getting in their face about the matter only increases the alienation. [Not saying that Sagan was hostile to religion -- just saying then next spokesperson cannot be.]