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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."
Billions of them pass through your taste buds every second. The problem is getting them to interact with your taste buds.
Technoli
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
CERN != Fermilab
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.
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!
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.
Our current fundamental laws don't need to be time symmetrical, they must respect what is called CPT (charge, parity, time reversal). Meaning that the laws of physics of a universe time reserved, with left and right interchanged (ie. spacetime goes (t,x,y,z) ->(-t,-x,-y,-z)) and particles interchanged with antiparticles are exactly the same. Two universes related by CPT are physically indistinguishable.
You can find experiments that portray time reversal violation by looking for CP violation. K^0 decays are an example.
First of all the asymmetry between matter and antimatter has been well known for something like 40 years. It was first seen in kaon decays and them more recently in b-meson decays. The issue has been that the size of the asymmetry has never been large enough to explain the universe being made of matter rather than antimatter.
A very fundamental result from quantum field theory is that the combined charge-parity-time symmetry(CPT) must hold or basically no quantum field theory works. Since we know that the quantum field theories that make up the Standard Model work very well, we're pretty sure CPT holds. Therefore any matter-antimatter asymmetry implies a corresponding time asymmetry.
However, these asymmetries are unlikely to explain the macroscopic arrow of time (why the future is different from the past). The answer to that question most likely comes from statistical mechanics.
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.
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
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.
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
Refresh your knowledge! You shouldn't be confusing chirality with helicity. You can change helicity by boosting to a faster moving frame of reference, but not chirality. Chirality is related to how the spinor transforms under Lorentz transformations. Both are the same in the ultra-relativistic limit (ie. 0 mass).
Weak interactions couple only to left-handed (as in chirality) spinors. There's no way you can change that with a Lorentz transformation, you would get ugly paradoxes if that were the case. Like the particle interacts in some reference frame but not in others...
By the way, gravity can actually create particles. In expanding universes like a deSitter space, the expansion creates particles in pairs. I must clarify I have verified this calculation only for scalar fields (I cannot confirm it right now for spin 1/2 particles). For further reading at this respect check Wald, QFT in Curved Spacetime and Black Hole Thermodynamics.
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.