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Fermilab Confirms Evidence of 4th Flavor Neutrino
eldavojohn writes "We've only had evidence for three kinds of neutrinos so far, but a recent test at Fermilab involving an antineutrino beam has reinforced a Michigan researcher's earlier experiment suggesting a fourth flavor. What's really odd about this is that a prior neutrino test (carried out as part of project MiniBooNE) did not result in indications of such strange oscillations. According to the researcher, 'The simplest explanation involves adding new neutrino-like particles, or sterile neutrinos, which do not have the normal weak interactions.' But this could also be an unknown or misunderstood effect. A Los Alamos National Laboratory scientist added that an explanation of this strange anomaly could result in understanding 'matter asymmetry of the universe, or why the universe is primarily composed of matter, rather than antimatter.' The results are published in the Physical Review Letters."
Will they be ever available in chocolate?
Sorry, I spilled my Fun Dip packet in there...
Living With a Nerd
4th flavor of neutrino; "I hope it's grape", that's just good comedy right there.
No, no, no the neutrino flavors follow the same pattern as basic emotions: Happy, sad, approving, disapproving and umami. Umami is a relatively recently discovered emotion. It feels like broth.
Some of my favourite people are from th US; Vonnegut, Chomsky, Bill Hicks.
Neutrinos again? Get back to me when they find something the size of a tennis ball:
Wouldn't that simply be a 4.48GHz radio wave? It's wavelength in a vacuum is approximately the size of a tennisball iirc.
Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj
Now, IANAPP (particle physicist), but I thought one of the things discrediting Heim Theory was the prediction of more than 3 neutrinos. What does the presence of a fourth neutrino mean for other predictions made by the current model? Does this mean that Heim's predictions may have more credence?
I think the bigger issues would be the wildly incorrect values for extremely well-known parameters (90ish sigma away from the measured mass of the proton, for instance) and the prediction of a "neutral electron" at a mass that should make it appear in pretty much every particle physics experiment EVAR.
Idiocist!
There are two kinds of people: 1) those who start arrays with one and 1) those who start them with zero.
CERN != Fermilab
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
Those guys in white coats all look alike to me.
We would know because everything would be spinning in the opposite direction. ;-)
Flannel shirts != white coats
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
What has been found is an excess of certain events (namely anti-muon-neutrino to anti-electron-neutrino oscillations), where "excess" is defined relative to the current best-established model. So what this experiment (if correct) shows, is that the current model is not good enough.
From the PRL paper:
The source of the excess remains unexplained, although several hypotheses have been put forward
One of those hypotheses is additional neutrino flavours, but this finding is not evidence for that.
The actual problem with Heim theory is that it predicted the existence of a neutral equivalent to the electron (per the theory, it should be commonly observed in particle interactions). The fact that such a particle has never been seen is considered a big strike against Heim.
I can't speak for people from a hypothetical universe and about what their naming conventions would be, but I can tell you that, given the known laws, the "anti-matter" universe would behave in exactly the same way as ours does.
No, this isn't true (unless time also runs backwards in the anti-matter universe).
Neutral Kaon decay violates CP - You can distinguish K0 decay in our universe from the anti-K0 decay in an antimatter universe.
It is conjectured that CPT symmetry does hold (therefore CP violation implies T violation)
http://en.wikipedia.org/wiki/CP_violation
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
The evidence for an asymmetry between matter and anti-matter has been growing for some time now (cosmological observations, recent muon experiments and now this). It used to be said that an antiparticle was a particle travelling backwards in time. So how does these findings affect our understanding of the asymmetry of time?
You will not drink with us, but you would taste our steel? - Walter Matthau, The Pirates
The scientific article does a reasonable job of making it clear that this result has a 0.5% probability of being produced entirely by background assuming that the systematics of the result are not playing evil games with you. While this result is interesting and it may, strictly speaking, "confirm evidence of 4th neutrino flavor" it only does so by being consistent with both a background fluctuation and some theories developed to describe a discrepancy similar to that seen in the data. It most certainly does not eliminate the standard model nor does it pick out any particular theory.
The MiniBooNE experiment at Fermilab reports results from a search for e oscillations, using a data sample corresponding to 5.66×1020 protons on target. An excess of 20.9±14.0 events is observed in the energy range 475EQE1250MeV, which, when constrained by the observed events, has a probability for consistency with the background-only hypothesis of 0.5%. On the other hand, fitting for e oscillations, the best-fit point has a 2 probability of 8.7%. The data are consistent with e oscillations in the 0.1 to 1.0eV2 m2 range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory. Yeah, well, no fine...
Excuse me, but please get off my Pennisetum Clandestinum, eh!
"Sterile neutrinos could also possibly help explain the matter asymmetry of the universe,
Isn't it a bit over confidence when assuming and hoping that a neutrino that only interacts via gravity can explain, or was responsible for Baryonic Asymmetry?. None of the *possible* explanations (CP-violation, more matter somewhere than antimatter, antimatter pushed somewhere else etc) I have read anywhere hinted that a hypothetical neutrino, and especially a sterile one, could explain asymmetry. So I am going to take that as a one scientist opinion and hope.
Well, IAAFPP (I Am A Former Particle Physicist, now no longer active in the field), and you have to be careful what you mean by "neutrino". In the Standard Model, neutrinos are partners to the charged leptons: electron, muon, or tau lepton. By "partner to", I mean connected (in a sense) by the weak force, which is the only non-gravitational force that acts on them (being neutral, they are immune to the electromagnetic force, and being leptons, they don't feel the strong force). Neutrinos are also very light, having near-zero mass.
This is what the Standard Model calls a neutrino. And there are, in fact, only 3 kinds. This was shown pretty convincingly by LEP at CERN. And it's also enough to discredit Heim's Theory (which no one really took seriously in the first place).
What this story is suggesting is that there may be a different kind of neutrino -- a so-called "sterile neutrino" -- that doesn't even feel the weak force. This isn't part of the Standard Model, but it is possible in certain extensions of the SM. This kind of neutrino doesn't act the same way as the SM neutrinos; it's a different beast, and comes about through a different part of the mathematics.
Since you are a /former) particle physicist, maybe you can explain me why it's not considered entirely natural that there are neutrinos which don't interact with the weak force. My consideration is the following: For each particle except the neutrino there are left-handed and right-handed versions. Only for neutrinos, only left-handed have been observed. Now what would a right-handed neutrino look like? Well, obviously it would not interact strong or electromagnetic, because after all it's a neutrino. But it also wouldn't interact weak, because it's right-handed. This would explain why it wasn't observed in experiments (because AFAIK Neutrinos are always observed through their weak interaction). On the other hand, it would interact gravitationally, and would therefore make a form of dark matter, without any extension to the standard model, except that one would drop the claim that there are only left-handed neutrinos. Since it seems strange anyway that neutrinos, unlike all other particles, only come in left-handed form, I'd expect that a "sterile" right-handed neutrino would be the natural assumption.
However the fact that particle physicists don't assume that, I guess there are good reasons not to assume it. So what is the problem with this reasoning? And could the sterile neutrino from this story be actually such a right-handed neutrino?
The Tao of math: The numbers you can count are not the real numbers.
http://cheezburger.com/View/4126230016
Your reasoning looks pretty sound to me; I don't think there is a fundamental reason to assume that right-handed neutrinos don't exist. I think the main reason people make that assumption is that there is no experimental evidence for it. It appears that the weak force only acts on left-handed particles
You're right in that a right-handed neutrino would interact only gravitationally. But if they exist, how did they get created in the first place? That creation process had to involve some combination of the other 3 forces -- gravity doesn't allow for particle creation or decay.
Another thing is that if it were massive (and it would have to be), it would have to have a left and right-handed component, and be invariant under Lorentz transformations. (One way to think about it is this: If it's moving in a certain direction, you could look at it from a reference frame moving even faster in that direction, and it would appear to be going the other way. This would change it from a right-handed to a left-handed particle, which would mean it could interact with the weak force, etc. etc. So it would have to be a mixture of both left- and right-handed components - you can't have a purely right-handed neutrino with a non-zero mass).
It also turns out (mathematically) that you can construct a (sterile) neutrino by using only left-handed fields, and still make it behave as if it had a right-handed component. This is the so-called "Majorana spinor". So you don't really need to invoke right-handed neutrinos, you can get the same result using just the left-handed fields.
Well, it's simple: At big bang, the matter went forward in time into our universe, and the antimatter went backward in time into the anti-universe. :-)
And there we have it. Maxwell's Demon, telling us how it all was done!
I don't understand why this should be considered strange. Scientists acknowledge that they have only gathered about 1% of the total amount of information available in the universe. Thus the study of the universe is in its infancy and thus new data that contradicts known data shouldn't be considered to be a "strange anomaly". Since when as knowledge gathered from the first 1% of the data in any large study been considered conclusive? Doesn't that missing 99% of the data say any conclusions drawn from the first 1% say that those conclusions should be considered as nothing more than preliminary suppositions?
"while democracy seeks equality in liberty, socialism seeks equality in restraint and servitude." de Tocqueville
Dude I totally just found it! Tennis balls are the size of tennis balls!
Boo-ya!
What's next? Ooh I know! I'll see if I can find something the size of a bowling ball! Now there's a challenge!
Now let's see... what could be the size of a bowling ball?
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
It doesn't really matter, the fact is there is more of one than the other, and whatever that other is is not what the universe is made of. If the universe were made of antimatter, all the rules would just be mirrored. Physicists can only guess as to why there is more matter than antimatter (again, names are meaningless, the point is that they are opposites), but it seems to come up consistently in the big particle accelerators.
Logically, they ought to be created in the same proportions, then cancel each other out completely. They aren't though, and because of that we exist. Why aren't they balanced? That's one of the big questions that needs an answer.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
Except antimatter is subject to the properties of space and time, it doesn't follow different rules for that. It is simply inverted matter - negative protons and positive electrons, but for every sub-atomic particle.
It's not like anti-matter somehow exists in a different space and time, it exists in our space and time. The Sun in fact spews out a small amount of anti-matter, and that definitely isn't moving backwards in time. We can create anti-matter on earth, and it doesn't go backward in time.
The idea, really, is silly.
The only thing really special about the matter-anti-matter relationship is that for some reason more matter gets created in these massive collisions of energy than anti-matter. If this were not so the universe as we know it would not exist.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
May I direct your attention to the three characters at the end of my post? Those letters are:
U+003A COLON
U+002D HYPHEN-MINUS
U+0029 RIGHT PARENTHESIS
You can learn more about the meaning of this character combination at Wikipedia.
Or to make it short:
WHOOSH!
The Tao of math: The numbers you can count are not the real numbers.
Cosmic Gall, by John Updike
NEUTRINOS, they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids down a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold shoulder steel and sounding brass,
Insult the stallion in his stall,
And scorning barriers of class,
Infiltrate you and me! Like tall
and painless guillotines, they fall
Down through our heads into the grass.
At night, they enter at Nepal
and pierce the lover and his lass
From underneath the bed-you call
It wonderful; I call it crass.
The only physicists I've ever seen in lab coats were in angles and demons.
Angles? Were they so acute they were obtuse?
The mind conceives, the body achieves, the spirit manifests.
So what is the problem with this reasoning? And could the sterile neutrino from this story be actually such a right-handed neutrino?
First: it cannot be dark matter because neutrinos are too light and hence move too fast. The result is that the WMAP cosmic microwave background would be blurred out far more than it is so we know that, whatever the dark matter is, it is slow moving and so not a light neutrino.
Second: MiniBoone has interesting results but have not BY ANY STRETCH of the imagination confirmed the existence of a 4th gen of neutrinos. Their signal is only 0.6% incompatible with background. To claim evidence the standard in the field is 3 std. dev. (or 0.27%) and to claim a discovery it is 5 sigma (0.000057%). Effects like this go away all the time and can easily be caused by errors. This is not a guarantee that theirs will but, to make claims like this you need solid, statistical evidence and they do not yet have that.
Third: we already know that right handed neutrinos exist because the neutrino has a non-zero mass. Any mass term in the Lagrangian mixes left and right helicity states. Effectively what this means is that if you have a left handed neutrino but chase after it faster than it is moving (which you can do because it has a mass) it will be a right handed neutrino to you. So, if there is anything interesting happening here, it is not a "normal" right handed neutrino.
Soo.. 2 wrongs don't make a right, but 3 lefts do?
Isn't Hawking radiation a process where gravitation creates particles?
Not really. It's an electroweak process that actually creates the particle-antiparticle pair.
Maybe a Higgs particle decays into a right-handed neutrino and something else?
No. "Decay" implies a weak interaction. And the weak force only interacts with left-handed particles (or more precisely with the left-handed fields, or components, of a particle).
The Higgs field can couple the left- and right-handed fields of a particle. But when you're talking about "Higgs particle decay", that's a weak interaction, which is only left-handed.
IIUC, if left-handedness depended on the frame of reference, then whether an electron (which very clearly has mass) can interact weakly would also depend on the frame of reference, and that doesn't make sense to me.
That's why you can't have a purely left- or right-handed massive particle. Any massive particle (like an electron) has to have both a left-handed and a right-handed (chiral) component. It also has to be invariant under Lorentz transformations, meaning that as you change reference frames, the particle looks the same. Only massless particles can be purely left-handed or right-handed, and for them chirality and helicity are equal. But not for massive particles.
By the way, the evidence of neutrino oscillations means that the three Standard Model neutrinos must have some non-zero mass, which means they're not purely left-handed. They were once thought to be purely left-handed, but that was when they were thought to be massless. Now we know that they're more like electrons, with a left- and right-handed component.
No they aren't, but I bet they have enough luminousity in their beam to make reconfirmation a bit easier. Maybe they'll shoot a neutrino beam at the detector;
If 8Gev is interesting imagine how exiting 7Tev would be! It's not like many of the neutrinos are going to hit anything between CERN and FermiLab.
Apocalypse Cancelled, Sorry, No Ticket Refunds
This is why I love particle physics. I am a scientists by training, but not a physicist, and while I have the sense that you two are not speaking gibberish, I can't be sure :) Or to put it another way, to paraphrase Arthur C. Clarke, "Any sufficiently advanced physics is indistinguishable from gibberish."
No, but depending on the characteristics of this new flavor (Aparently more unstable than the 3 known flavors, due to scacity in detecting them) they might decay into more mundane neutrinos while in transit.
Now, a worthwhile experiment would be to generate neutrinos at CERN, detect a sample in the CERN collector, then have that same stream collected at FermiLab, and compare sample populations as recorded by the two detectors. That would give you some more hard data concerning rates and specificities for neutrino decay, which would be academically useful.
At 7 TeV you'd have some attenuation of the beam (or some percentage of neutrinos absorbed between the creation and detection); and to confirm the same effect at a distance 20000 times bigger, you'd need ~20000 times more energy than MiniBooNE, so that would be 160 TeV (or "quite much more than the LHC"). What the LHC could do is to make a lower energy antineutrino beam and direct it to other European lab, with an energy such that the distance to the lab divided by the beam energy is around the same as MiniBooNE. That would give us a third confirmation of the same effect (after LSND and MiniBooNE), with much higher statistics.
Neutrino decay isn't 100% excluded as a secondary effect; but the indirect result of the existence of a fourth neutrino has nothing to do with it.