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Questions tagged [neutrinos]

Neutrinos are light, uncharged leptons. The neutrino tag should be applied to question relating to neutrino properties or interactions involving neutrinos.

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Are neutrinos or antineutrinos more prevalent?

As I understand it, neutrinos were first proposed to explain energy and momentum conservation in beta decay, as a hypothetical particle emitted together with the electron and proton. Thus Pauli gave ...
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315 views

Neutrino energy density vs photon energy density

So I'm currently following a course in Cosmology and we're covering the densities of different species in the universe right now. Starting from the photon density $\rho_{\gamma}$ we need to derive the ...
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Lack of knowledge about ambient neutrinos below a certain energy?

A colleague and I were discussing the fact that beta decay can emit neutrinos with arbitrarily low energies. We have neutrino detectors that can detect solar neutrinos -- and maybe extrasolar ...
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Can we create negative mass this way? [closed]

First,sorry for the clickbate(kinda). I don't know if this will work or not but It seems worth a shot unfortunately I am stuck on the approach of proving it can't be done.....'cause ofcourse it can'...
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1answer
45 views

Looking for an understanding of Toroidal Moments [duplicate]

The wikipedia page is not so enlightening Apparantly the Neutrino, if it is a Dirac particle, has a Toroidal Moment. Does this mean the Dirac neutrino would interact electromagnetically as well as ...
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Why Neutrino is a ghost particle?

why neutrinos are called ghost particle.why it is not affected by strong magnetic field. why it does not interact with matter. why it does not interact with gravitational field? I am unable to ...
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Quantization of the massless neutrino field

If a massless neutrino or anti-neutrino is considered (in the whole post I consider neutrinos res. anti-neutrinos as mass-less), it is described by the Weyl-equation: $$\overline{\sigma}^{\mu}\...
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The basics of neutrino telescopes

I'm trying to understand the basic operation of the ANTARES neutrino telescope. Here is what I've gathered: The detection of neutrinos relies upon the detection of muons. Cosmic rays and neutrinos ...
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Energy dissipation from a black hole by neutrinos

Could the high gravitation field of a black hole cause neutrinos to form a Fermi gas or superfluid? Could these neutrinos from the neutrino background of the big bang whose temperature and deBroglie ...
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What is the difference between a neutrino and an electron neutrino?

So, what is the difference between a neutrino and an electron neutrino? Like how does the term 'electron' made a difference? Also, what is the difference between an antineutrino and an electron ...
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Are neutrinos just different states of a single particle, in essence?

When Neutrino oscillation phenomenon is analysed quantum mechanically, it is said that, \begin{align} |\nu_e \rangle &= \cos(\theta) | \nu_1 \rangle + \sin(\theta) |\nu_2 \rangle,\\ |\nu_\mu \...
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Is there a bound on the number of sterile neutrinos from cosmological observations?

The right-handed sterile neutrinos $\nu_{R}$ are electroweak singlets. They do not contribute to the electroweak anomaly, and therefore, their number is not fixed by the requirement of the anomaly ...
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Why is it doubtful that higgs field gives neutrino mass?

I read some articles mostly claiming that if neutrino is their own antimatter than they could get their mass from some other source rather than the higgs field, and I can't probe any further because ...
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Is anti-sterile neutrino possible?

Due to the surplus of electron neutrino led people to suggest the possibility of 4th neutrino flavour, and it is thought to only interact with gravity and nothing else not even weak interaction. So is ...
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1answer
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Can neutrinos change chirality by oscillating?

Active neutrinos are left-handed while sterile neutrinos are right-handed. There are speculations that active neutrinos can oscillate into sterile neutrinos. Can neutrinos change chirality by ...
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26 views

Majorana Neutrinos in the KamLAND-Zen

I'm reading the following paper concerning the KamLAND-Zen experiment "Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen" In the second paragraph of the first ...
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Why should $\nu_\mu\to \nu_e$ oscillations be expected to be unobservable in short baseline experiments?

The blog here says On the other hand, several rogue experiments refuse to conform to the standard 3-flavor picture. The most severe anomaly is the appearance of electron neutrinos in a muon ...
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Universe under Point Reflection — or why is the Neutrino not its own anti-particle?

The spin of a anti-neutrino points into the same direction as its momentum. The spin is a cross-product, so under point reflection it remains the same, whereas the momentum gains a factor of $(-1)$. ...
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If neutrinos are disfavoured as DM candidates why aren't axions?

Numerical simulations of observed large-scale structure formation work best with Cold Dark Matter (CDM; see the answer here). Neutrinos are candidates for Hot Dark Matter (HDM), and hence they cannot ...
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Estimate of neutrino masses from the values of $\Delta m_{21}^2$ and $\Delta m_{13}^2$ only!

The blog here says that The measured mass differences between the eigenstates are $\Delta m_{21}^2=7.5\times 10^{-5} {\rm eV}^2$ and $\Delta m_{13}^2=2.5\times 10^{-3} {\rm eV}^2$, suggesting that ...
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1answer
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Why we can know what flavor the neutrino is created but not their mass? [duplicate]

All neutrino knows which of the 3 flavours they must be upon their creation, however their mass becomes uncertain... why is that? isn't mass supposed to tie to which ever flavours like for example an ...
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High intensity laser and neutrino pair production

Given the very small rest mass of the neutrino, visible photons have plenty energy for neutrino pair creation. What would be the probability of $\gamma \to \nu + \bar\nu$? Would the neutrinos be ...
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How can individual neutrinos have different amounts of energy?

Photons have no mass, travel at the speed of light, and their energy is related to their frequency. Neutrinos have a very small mass, travel at almost the speed of light; what is their energy related ...
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Which experiment could resolve the neutrino mass hierarchy problem?

Neutrino oscillations are sensitive to $\Delta m^2$, but not to the absolute mass scale, therefore we have the problem of the mass hierarchy. Which experiment could resolve this problem? Is there any ...
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Symptoms of lethal neutrino radiation in a hypothetical scenario

Core collapse supernovae release the majority of their energy in the form of neutrinos. According to an XKCD What If, the neutrino radiation alone from a supernova at a distance of just 2 AU would be ...
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Neutrino's relativistic four-momentum

In an exercise I have to solve there is an apparently contradiction that I can't figure out. In a pion decay, where a muon and a neutrino are produced, conservation of quadric-momentum states: \begin{...
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Light neutrino number from the invisible decay width of $Z$ boson, and precluding heavy neutrinos as dark matter candidate

The $Z$ boson decays into pairs of quarks and leptons. While the decays to quarks pairs and charged lepton pairs can be observed, the decays to $\nu\bar\nu$ are cannot be. By subtracting the visible ...
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Energy density, pressure and temperature for massive neutrinos in cosmology

I want to be able to numerically compute the mean energy density and pressure for a massive neutrino species in cosmology, at any given scale factor $a$. These are given in terms of the distribution ...
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So is it not $CP$ instead of $C$ that is responsible for changing a particle to its antiparticle?

The charge conjugation operator $C$ reverses the charge of a state. But it may or may not convert a particle to its antiparticle. For example, consider a neutrino which is charge-neutral and left-...
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Ratio between neutrino scattering cross-sections

I would like to calculate the ratio between the cross-section of the processes: $$\frac{\nu_\mu+e^- \rightarrow \nu_e+\mu^-}{\bar{\nu}_e+e^- \rightarrow \bar{\nu}_\mu + \mu^-}$$ I found this set of ...
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How to discern between the accelerator and atmospheric neutrinos in detectors?

If an experiment is detecting accelerator neutrinos, then how can one distinguish the accelerator $\nu_{\mu}$-neutrinos from the atmospheric $\nu_{\mu}$-neutrinos? As I know, both of these types of ...
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270 views

How much energy does a neutrino have? [closed]

Neutrinos were theorized when some energy was noticed to be 'missing' from beta decays, correct? But until recently, they were thought to be massless. So, how much energy does a single neutrino have?...
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How is the fraction of a particular neutrino species calculated?

Suppose we assume that a neutrino is formed in the $\left| \nu_2 \right>$ eigenstate. Then, \begin{align} \left| \psi(x, t) \right> &= \left| \nu_2 \right> e^{-i\phi_2} \\ &= \left(...
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Why neutrino energy threshold in inverse muon decay is so high

In the interaction: $$\rm \nu_\mu + e\to\nu_e+\mu$$ the $\nu_\mu$ energy threshold to produce the process is $m_\mu^2c^2/2m_e$, which gives a $\sim10~\rm GeV$ threshold. For the same muon neutrino ...
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91 views

Matter effects contributing in solar, atmospheric and reactor neutrino oscillations

Neutrino oscillations are affected by the matter effects. For solar neutrinos, which are exclusively neutrinos of $\nu_e$ type, the matter effects can be contributed by (i) the solar plasma, (ii) ...
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Effect of temperature on neutrino oscillations?

We know that while propagating through space, neutrinos changes their identities continuously.i.e., they oscillate from one flavour to another while travelling. This phenomenon suggest that neutrinos ...
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What is meant by the absolute scale of the neutrino mass?

In this review titled "Pieces of the Flavour Puzzle" the author Ferruccio Feruglio wrote in the introduction that "The origin of the parameters in the flavour sector of the Standard Model (SM), ...
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Mean free path for $3\rightarrow 1$ scattering

I want to calculate the mean free path of an antineutrino in nuclear matter where it can undergo the reaction $p+e^-+\bar{\nu} \rightarrow n$, which I imagine will involve calculating the rate of that ...
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Why is it so important to measure CP violation in the lepton sector?

CP violation has been measured in the hadronic sector (K-mesons, B-mesons) and these baryons can decay into leptons, so why is it so important to measure direct CP violation into the lepton sector? I ...
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Why is the notion of neutrinos as possiblly Majorana fermions still promoted given the observation of neutrino oscillations?

A Majorana particle is a fermion whose antiparticle is itself. In other words, a Majorana fermion has only two components, rather than 4 components for a Dirac fermion. Neutrinos are alleged as ...
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Why Majorana neutrinos is a solution for the existence of only LH neutrinos?

At lesson my teacher stated that the possible reason for why only LH neutrinos are observed are that either: neutrinos are Dirac fermion but the RH neutrinos are not interacting weakly or that they ...
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Are other ways of neutrinos being “destroyed”? [closed]

I understand that neutrinos are absorbed and such, but are there any other way for neutrinos to be "destroyed" per se?
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Why is IceCube more sensitive to Northern hemisphere events?

I am reading about neutrino detectors, especially about IceCube Neutrino detector and while going through some papers I found the statement "IceCube is more sensitive to point sources in the northern ...
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What caused neutrinos to decouple at $t=1$ second?

Was it simply that the density and/or kinetic energy got too low, because of expansion? Or was it something about the weak force itself (which I thought gelled around $10^{-10}$s? For the CMB, ...
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1answer
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Why are neutrino flavors equal to 1:1:1 after a long travel?

Neutrinos produced in the interaction of very high energy cosmic rays with the CMB are produced in the proportion $\nu_\mu:\nu_e:\nu_\tau=2:1:0$ because of the decays produced after the cosmic ray ...
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1answer
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Charged Current $\nu_\mu+e^-$ interaction?

Basically I want to know if there is something that forbids an interaction like $$\nu_\mu+e^-\rightarrow\mu^-+\nu_e$$ Having a look at the effective fermi interaction charged current lagrangian $$\...
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1answer
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Is there an apparatus that measures neutrino spin?

Anytime any reference is made to spin at the quantum level the Stern-Gerlach experiment is sited for reference. I was curious how individual particles "atoms" or subatomic particles are isolated to ...
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A fourth (sterile) neutrino existence and quark generations

Would the existence of a fourth (sterile) neutrino imply the existence of a fourth generation of quarks and a fourth lepton, beyond electrons, muons and tau particles?
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How can a neutrino detector tell the difference between the three types of neutrinos?

In other words, what is the difference between the three flavors of neutrino? Most articles talk about how they are created differently, but not about what actually distinguishes them from ...
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Have all three flavors of solar neutrino been measured?

As far as I know that the sun exclusively produces electron neutrinos ($\nu_e$). When the flux of solar neutrinos ($\nu_e$) is measured on the earth, a depletion is observed in the $\nu_e$ flux i.e., ...