# Tag Info

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Last (?) Edit: The "problem" is solved: it was mainly a problem in the timing chain, due to a badly screwed optical fibre. A high level description of the problem is given here and a more detailed explanation of the investigation is here. List of possible systematic biases I thought it might be a good idea to list the possible systematic biases which could ...

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It's very hard to imagine that there is any sensible model consistent with OPERA's results. (Aside from models of unaccounted-for systematic uncertainties in the experiment.) We know that we live in a world described to very high precision by Lorentz-invariant quantum field theory, so the most sensible way to look for Lorentz violation is to start with such ...

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I am afraid that one has to go to a "very unusual segment" of theoretical literature if he wants any papers about superluminal neutrinos. Guang-jiong Ni has been authoring many papers about superluminal neutrinos a decade ago: http://arxiv.org/abs/hep-ph/0103051 http://arxiv.org/abs/hep-th/0201077 http://arxiv.org/abs/hep-ph/0203060 ...

21

Dark matter can be hot, warm or cold. Hot means the dark matter particles are relativistic (kinetic energy on the order of the rest mass or much higher), cold means they are not relativistic (kinetic energy much less than rest mass) and warm is in between. It is known that the total amount of dark matter in the universe must be about 5 times the ordinary ...

21

Is this even remotely possible? Well... "possible," yes, but kind of like how tunneling through a brick wall is "possible": while you can't definitively prove it impossible, you'd feel pretty safe saying "this will never happen." Relativity is really well-tested, and it's really hard to conceive of a way that neutrinos could travel faster than ...

20

They are probaby talking about supernovae, like how SN1987A was first detected by neutrinos before the light arrived. In that case neutrinos and photons are both produced in the core of the supernovae explosion, but they have dense clouds of gas to get through before they get to empty space and travel freely to us. Since the neutrinos are weakly interacting ...

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Cute question! For a neutrino with mass $m$ and energy $E\gg m$, we have $v=1-\epsilon$, where $\epsilon\approx (1/2)(m/E)^2$ (in units with $c=1$). IceCube has detected neutrinos with energies on the order of 1 PeV, but that's exceptional. For neutrinos with mass 0.1 eV and an energy of 1 PeV, we have $\epsilon\sim10^{-32}$. The time of flight for ...

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The neutrinos are coming straight at us. Indeed, their interactions with anything along the way are minimal at best. The reason the image is so big is that the angular resolution of the detector is rather poor (compared to, say, an optical telescope). This is not unexpected when it comes to neutrino telescopes. The details of how the detector work are ...

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The detector that took that image--Super Kamiokande (super-K for short)--is a water Cerenkov device. It detects neutrinos by imaging the Cerenkov cone produced by the reaction products of the neutrinos. Mostly elastic scattering off of electrons: $$\nu + e \to \nu + e \,,$$ but also quasi-elastic reactions like $$\nu + n \to l + p \,,$$ where the neutron ...

19

Before I answer, a couple caveats: As Adam said, the universe isn't going to start behaving any differently because we discovered something. Right now it seems much more likely (even by admission of the experimenters) that it's just a mistake somewhere in the analysis, not an actual case of superluminal motion. Anyway: if the discovery turns out to be ...

17

Depends on the detection technology. Yes Cerenkov based detectors (SNO and Super-Kamiokande for instance, as well a many cosmic ray neutrino detector) are direction sensitive, and this is one of the design considerations that drive the use of this tricky technique. The best results come from quasi-elastic reactions like $\nu_l + n \to l^- + p$. The ...

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You have a few longer answers which were already updated, but here is a concise statement of the situation in mid-2014: An independent measurement by the ICARUS collaboration, also using neutrinos traveling from CERN to Gran Sasso but using independent detector and timing hardware, found detection times "compatible with the simultaneous arrival of all ...

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There are other neutral particles with antiparticles, such as the neutron and the $K^0$ meson. In those cases we have a microscopic theory that says those particles are made of quarks: for instance, the $K^0$ is made of a down quark and an anti-strange quark, while its antiparticle the $\bar K^0$ is made of a strange quark and an anti-down. The neutrino is ...

15

This is how the north pole looks: The sea ice at the North Pole is typically around 2 to 3 m (6 ft 7 in to 9 ft 10 in) thick. and this is how the south pole looks : The ice is estimated to be about 2,700 metres (9,000 ft) thick at the Pole, so the land surface under the ice sheet is actually near sea level.2 This is the ice cube neutrino ...

15

The calculation is done for 1987A here. Basically, the neutrinos' fractional speed increase from the new paper is $2.48\pm0.28\pm0.30\times10^{-5}$ (statistical / systematic errors, respectively) . SN1987a was $166\,912\pm10.1$ ly away, so multiplying the fraction by the travel time gives $4.14\pm0.97$ years. In reality, we got the neutrinos a few hours ...

14

Neutrinos have mass and travel slightly below light speed, therefore an inertial frame for the neutrino exists, while it doesn't exist for a massless photon which travels exactly at $c$. We don't know the masses of the neutrinos, but neutrino oscillations tell us that the three neutrino families must have a mass difference. For all we know, one of the three ...

13

The answer is yes. Neutrinos will travel faster than light in a medium with a refractive index ($n$) greater than one (which is the case of air). Indeed the speed of light in that medium will be $v_{\text{medium}}=c/n$ where $c=2.998\times10^8$ m/s and $n>1$. Then, because neutrinos interacts only very weakly (only through the weak nuclear force) with ...

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Short answer: Unknown Slightly longer answer: the situation you describer would obtain if neutrinos were Majorana particles (and thus not Dirac particles). It is favored by theorists because it feeds into a nice explanation of why the neutrinos are so light by comparison to the other massive particles. Experiments are underway that might settle the ...

13

The historical formulation of the SM involved one Higgs doublet and only renormalizable couplings, the latter being due to the focus at the time on achieving a renormalizable formulation of the weak interactions. With these restrictions neutrinos are massless and do not oscillate. To get neutrino masses you need to extend this framework either by adding ...

12

It seems that theoretically neutrino stars have been postulated. A google search came up with Supermassive neutrino stars and galactic nuclei. R.D. Viollier, D. Trautmann and G.B. Tupper. Phys. Lett. B 306 no. 1-2 (1993), pp. 79-85. The calculations have been done for you :) if you have access to a library: Abstract The characteristics of ...

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Possible extragalactical sources for high energy neutrinos is still an open question. There are several candidates, look at this paper on arXiv. By the way, astrophysical neutrinos have been already detected more than 20 year ago by Kamiokande in Japan. They came from supernova SN 1987A, and helped to set an upper bound (of about $10\ \text{eV}$) on the sum ...

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It is technically impossible to measure the speed of such a particle directly; and it all depend on "which" neutrino you are talking about. The speed is related to the momentum and the momentum to the energy. So you can have a neutrino of some MeV of total energy, another one of some GeV, etc. But in any cases, the answer will be "very very close" to c. ...

11

The basis of all neutrino beams is a less exotic (protons most of the time) beam smashing some mundane target and making scads of assorted particles---many of them charged. Those charged particles are focused (and possible subjected to a second filtering for energy by using collimators and more magnets, though this step is not being done at CERN), then they ...

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UPDATE 2011-10-15 This phenomena may have been explained. The crux of the problem had to do with differing reference frames - the distance traveled according to the satellites which measured the time was different from the distance traveled according to us on earth. If you're going to measure speed (distance / time), you have to get the distance and time ...

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The photon does couple directly to charged stuff, e.g. via Compton scattering. This is indirectly related to the spin, as direct interactions between fermions are hard to construct. The neutrino on the other hand does not couple immediately to any other matter particle. It requires a force-carrier. Now as it turns out the only force carriers that care about ...

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No. Ordinary supernovas do not produce neutrinos of large enough energy to cause such a nuclear weapon meltdown, even if the inverse square law diminution of flux is not an issue. The original paper on which the NewScientist based its article is the preprint Sugawara, H., Hagura, H., Sanami, T. Destruction of Nuclear Bombs Using Ultra-High Energy ...

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Instead of the massive compact objects which could serve as a 'replacement' for the supermassive black hole inside the galactic center (which are discussed in the Viollier and Tupper paper from Anna's answer) I would like to point another possibility: halos of degenerate neutrino gas around galactic clusters. The order of magnitude calculations for the ...

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According to Dr. Phil Plait, there's a rumour that it's been a faulty connection. In summary: nothing is wrong with the calculation, the theoretical assumptions, rotation of the Earth, etc... A hardware problem caused the 60 ns time gap. It's still gossip, so take this with abundance of caution, but here's what he had to say: According to sources ...

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Here is a pdf file with the letter in both German and English. Screenshot:

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Whether or not neutrinos would be suitable for rapid trading, people have seriously considered their utility for signalling in difficult environments. I read an article a while back about a paper (published in Phys. Lett. B, but I can't access that from here) by Patrick Huber which proposed using neutrinos for through-the-earth communication to submarines as ...

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