# Tagged Questions

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### What is the meaning behind the neutrino oscillation parameter?

As far as I can tell, there are 6 parameters that describe how a neutrino oscillates: 2 mass squared differences, 3 mixing angles and another parameter I don't understand at all (delta). Thus I have ...
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### Can a neutrinos mass oscillate in a similar way to its flavour?

So I've been reading up on neutrino oscillations and I think I'm making some progress in understanding it, but I'm still a long way off. As I understand it, you can 'classify' neutrinos in two ways; ...
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### Unitarity of PMNS matrix

Why should the neutrino mixing matrix (PMNS matrix) be unitary? Is the unitarity dictated by experiments or is it a theoretical demand?
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### Majorana Mass For Neutrinos In Standard Model

Neutrinos can't be given Dirac masses because there is no $SU(2)_L$ singlet right handed neutrinos in the standard model. But can neutrinos be given Majorana masses in the standard model? EDIT: Why ...
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### Oscillations and Majorana Neutrino

In neutrino oscillations, neutrinos can convert from one flavor to another. This implies individual lepton number is not conserved. Doesn't it also imply that, if the neutrinos have mass, the mass ...
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### Question about Majorana fermion and Majorana representation

In Chiral representation, a Majorana spinor looks like: $$\psi=\begin{pmatrix} \psi_L\\ -i\sigma^2\psi_L^*\end{pmatrix}$$ In this representation the Right handed field is the charge-conjugate of ...
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### Confusion With Neutrino Oscillation

Neutrinos produced in the weak interaction are eigenstates of the weak interaction hamiltonian or flavor eigenstates. Right? If this is so, then $\nu_e,\nu_\mu,\nu_\tau$ should be the stationary ...
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### Writing Dirac Mass Term For Massive Neutrinos

How does one write down the following Dirac mass term for a collection of "massive" neutrinos? $$-[\overline{(\psi_R)}M_D\psi_L+\overline{(\psi_L})M^\dagger_D\psi_R]$$ I ...
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### Neutrinos and anti-neutrinos in the Standard Model

In standard model neutrinos and the left handed electron forms SU(2) doublet. What about the anti-neutrinos in the standard model? Do they also form some doublet? If neutrinos have tiny masses will ...
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### Fusion of two neutrinos

What are the results of fusing an electron neutrino and a muon neutrino? If you have an answer, then why? I looked this up and searched for stuff on Google, Wikipedia and a few other sites, but all ...
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### Sterile Neutrinos and Supersymmetry

Just read a Scientific American review of a recent article which suggests evidence for sterile neutrinos: ...
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### Do neutrinos not couple to the Higgs field?

I was reading the CernCourier, my favorite source of message on Higgs and friends. I was rather shocked, when I saw this: "The mechanism by which neutrino mass is generated is not known." What? ...
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### Massless neutrinos and Chirality

The massless neutrinos can be represented by two component Weyl spinors. Then how does one say that it is an eigenstate of the chirality operator $\gamma^5$, which is a $4\times 4$ matrix and can act ...
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### Why positronium can annihilate in vacuum?

I thought that the annihilation process of positronium cannot take place without a third-party particle. This can be directly derived from energy & momentum conservation: energy conservation: ...
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### The delay between neutrinos and gammas in a supernova, and the absolute mass scale of neutrinos

In a supernova explosion (of some type), there is a huge amount of neutrinos and gamma rays produced by a runaway nuclear reaction at the stellar core. In a recent comment, dmckee noted that the ...
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### What sorts of complications do massive neutrinos bring to the Standard Model?

Naively, I'd just think of considering them as any other massive fermions (but without electric charge), including the appropriate chiralities (and neutrino-higgs coupling when necessary). ...
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### Pair production of neutrinos

I learned that neutrinos have a much lower energy than electrons. Pair production of electrons occurs when the photon energy is above 2 times the energy of an electron. So I am wondering if pair ...
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### Statistics followed by Neutrinos [closed]

What does the neutrino particles follow- Dirac or Majorana Statistics?
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### Question about Neutrino Flavor and Mass Eigenstates

I know the flavor and mass eigenstates are different, but are they related? What I mean is, in a process like fusion where electron neutrinos are created, do they start in the 1 mass eigenstate? My ...
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### How quickly do neutrinos change flavor?

DOE’s Fermilab has switched on its newly upgraded neutrino beam. This is in preparation for the NOvA experiment, which will study neutrinos using a 200-ton particle detector at Fermilab and a ...
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### Controlling Neutrinos for Communication

Neutrinos travel straight through earth at the speed of light. Therefore, it seems that they could be great for intercontinental communication. Of course, I assume a lot still needs to be learned ...
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### Neutrino power plant

Suppose there is a material that interacts with 50% of high-energy neutrinos. To what temperature such material will heat up naturally here on Earth? What power can be extracted from it?
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### Slowing down high energy neutrinos?

Which atoms can slow down high energy neutrinos? I mean in which medium high energy neutrinos will tend to slow?
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### Neutrinos: how can they carry information about universe?

I know that neutrinos are particles with a very small mass and no electric charge. They infrequently interact with matter and so they can give us information about the "old" universe. But how can they ...
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### Why aren't there more than three generations of the leptons and quarks? [duplicate]

There are three generations of electrons, neutrinos, and quarks. The second and third generations of electrons and quarks are unstable and decay into lighter particles. Why are there exactly three ...
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### Do neutrinos of any flavor get trapped in black holes?

This question has been bothering me a bit. I know that neutrinos have super small mass and they interact via the weak force. Since they have a non-zero mass, they should be affected by black holes and ...
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### How much energy is carried away by neutrinos in matter-antimatter annihilation?

Some people say that neutrinos carry away most of the energy, some others say just a fraction. So what is the truth ? what is the percentage of energy lost due to neutrinos ?
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### Mechanisms of mass generation for Dirac neutrinos

If neutrinos are Majorana particles, one way of explaining their small masses is the seesaw mechanism. Now say I'd like my neutrinos to be Dirac, for symmetry to the quark sector. What mechanisms ...
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### What is difference between the different 'flavours' of neutrinos?

Moreover, how-come scientist know that muon-neutrino are different from electron-neutrino when they didn't even know what the difference was? Did they interact differently with other particles?
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### Neutrino mass with Dirac and Majorana

Why both Dirac mass and Majorana mass terms are needed to explain the mass of a neutrino?
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### Are right handed neutrinos actually antineutrinos and vice versa?

Is it experimentally ruled out that right-handed neutrinos are actually antineutrinos, and left-handed antineutrinos are neutrinos ?
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### Neutrino Oscillation and their gravitational implications

As I understand neutrinos, there are three different flavors, all with different masses. Although the masses of these neutrinos have not been directly measured, their mass differences have been. ...
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### “Conceptualizing” neutrinos

Layman here. EE and BS physics. I am "content" in viewing photons/electromagnetic radiation as an "emergent" property of spacetime? due to the electrons ("particles..?") and all their activity jumping ...
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### Neutrino and electromagnetic forces

I learned from Wikipedia that neutrinos "are not affected by the electromagnetic forces". How was this identified experimentally?
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### Neutrino Oscillations and Conservation of Momentum

I would like to better understand how neutrino oscillations are consistent with conservation of momentum because I'm encountering some conceptual difficulties when thinking about it. I do have a ...
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### Are there any reasonable attempts at explaining the OPERA result

as there's so many papers on the opera result and it's a struggle flicking through them all combined with my limited knowledge meaning I cannot well differentiate silly nonsensical papers from ones ...
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### How do we know Dark Matter isn't simply Neutrinos?

What evidence is there that dark matter isn't one of the known types of neutrinos? If it were, how would this be measurable?
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### Where did the idea of a neutrino come from?

Exactly what paper by W. Pauli introduced the idea for the existence of a neutrino and how was its existence confirmed experimentally (who did that and in what paper)?
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### How is the distance between Geneva detector and the Gran Sasso one measured?

Does anyone know how is the distance between detectors in the now famous neutrino experiment measured? Also, how was the time of flight measured?
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### How are neutrino beams emitted at CERN?

As far I know they come from accelerator collisions, but I have read confusing things like magnetically focused. How could neutrinos be guided magnetically if they aren't affected by the ...
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### What are the implications of superliminal neutrinos? [duplicate]

Possible Duplicates: What would be the immediate effects if light does not go at the maximum speed possible? Superluminal neutrinos Do we re-write physics? Or can it be fitted in current ...
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### Models of neutrinos consistent with OPERA's results

I guess by now most people have heard about the new paper (arXiv:1109.4897) by the OPERA collaboration which claims to have observed superluminal neutrinos with 6$\sigma$ significance. Obviously this ...
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### What happened to the idea of tachyonic or other superluminal neutrinos?

While hunting around for information about the recent OPERA measurement that hints at superluminal neutrinos, I discovered that this idea was actually considered back in the 1980s. Wikipedia lists as ...
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### What would be the effects on theoretical physics if neutrinos go faster than light?

Earlier today, I saw this link on Facebook about neutrinos going faster than the speed of light, and of course, re-posted. Since then, a couple of my friends have gotten into a discussion about what ...
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### Elastic collisions with neutrinos

1: Do neutrinos undergo elastic collisions with fermions? 2: Would this imply a variable speed for neutrinos? 3: Can neutrinos transfer momenta in interactions?
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### muon neutrino momentum distribution

muon neutrino momentum distribution I have read the public data of T2K ,KEK to find this subject, I'm curiously that it's coincides with my prediction perfectly: The neutrino get its momemtum by its ...
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### Neutrino versus Anti-neutrino Detection

Is there a that detection method in use that can distinguish between a neutrino from its anti-neutrino?
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### Are neutrinos Majorana particles?

That is, are they identical to their anti-particles? (Any results of double beta decay experiments?)