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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Neutrino Free streaming
I want to get to the relation which is the neutrino free streaming scale $K_{fs}$, at $\frac {T_{\nu,0}}{a^2}= \frac{1.946}{a^2}$
which is:
$K_{fs}=\frac{1}{X_{fs}}$
Finally what I want is
$K_{fs}=3.2 ...
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What happens when an anti-electron collides with a neutrino?
What happens when an anti-electron collides with a neutrino? If something does happen, is a photon released after the collision?
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To understand modern concepts in the field of Neutrino physics and the field on the whole what are the mathematical prerequisites that I need? [closed]
I want to start working in the field of Neutrino Physics but I am not mathematically well equipped, and I cannot bypass this as it is crucial to the field, what mathematical topics or concepts should ...
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What is the mechanism for neutrino emissions from a black hole
In Black Holes and Time Warps, Kip Thorne describes a conference he and Stephen Hawking took in the 1970's where Hawking discussed black hole evaporation. He discussed radiating gravitational waves ...
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What mass do neutrinos have in the early universe?
Since neutrinos interact constantly in the early universe, I assume that they are present as flavor eigenstates. However, they are Fermi-Dirac distributed,
\begin{equation}
f(E, T) = \frac{1}{e^{E/T} +...
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Solar neutrino deficit, 1/3 or 1/2?
The puzzle of the missing solar neutrinos is supposedly solved by neutrino oscillations. I understand the mechanism, but there is still one point which I find unclear.
For the energy range and ...
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Neutrino oscillations and neutrino mass measurement
At the KIT they have been measuring the mass of the electron neutrino with a huge spectrometer (i.e. they make an enormous effort) and already published limits on the highest possible electron ...
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Difference between $Q$ value and Total energy in a beta minus decay
I was going through the kinematics of beta minus decay. I understood that the $Q$ value in the beta minus decay is the sum of the KE of electron and anti-neutrino
$$Q= E_e + E_\nu.$$ Here the $E_e$ ...
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Distinction between majorana neutrinos and sterile neutrinos
I am a bit confused about Majorana neutrinos. A generic Dirac spinor can be written in terms of his left and right-chiral components as
$$
\psi = \begin{pmatrix} \psi_L \\ \psi_R \end{pmatrix}
$$
A ...
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Do cosmological neutrino-antineutrino pairs annihilate at all?
Do low energy cosmological/relic neutrino-antineutrino pairs annihilate to produce photons at all? Their energy is presently too low to produce electron-positron pairs but there should be an indirect, ...
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Meaning of short, medium and long baselines
I was reading about the experiments on Neutrinos and came accross terms like "Short", "long" and "medium" baseline experiments. Can anyone please tell me how do we define ...
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Can we determine the polarization of a neutrino?
I recently read that neutrinos have a polarization property---their polarization is opposite to antineutrinos.
Is it possible to determine the polarization of a neutrino? For example, we can determine ...
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How is the chirality for the weak interaction conserved for non-relativistic neutrinos?
In this article, one can read that the neutrinos in the cosmic neutrino background have a speed of about 1/50 of the speed of light, which is clearly non-relativistic.
From the viewpoint of, say, ...
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How long does it take before neutrino velocities in the neutrino background radiation are substantially less than the speed of light?
The energy of photons is reduced by the expansion of space. Since the photons have been decoupled from matter their wavelengths have decreased from the visible range to the radio range.
The same ...
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Neutrino Mass from Tritium
I just read: Researchers close in on the elusive neutrino (phys.org)
However, I think I'm missing something. The basic argument appears to be:
(decay process)
Tritium -> Helium-3 + β− (electron) +...
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The chirality of the standard model fermions
I read 'The Standard Model Effective Field Theory at Work' by Isidor, Wilsch, and Wyler. In a footnote, they say that, in principle, right-handed neutrinos could be included in the Standard Model by ...
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Helicity of cosmic neutrinos
If neutrino has mass, then it can change it's helicity. But all registered neutrinos have negative helicity while all anti-neutrinos have positive.
Does it stands for all registered neutrinos ...
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Feynman diagram: Two-way arrow in the fermion propagator line?
I have encountered some diagrams (like the example below) where two lines coming out of a single vertex (in this context, right-handed neutrino $N^c$) have opposite direction. In a usual diagram, a ...
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Cloud Chamber Help Needed! [closed]
I was inspired by this video to attempt to create a cloud chamber without dry ice (it's very challenging to get where I live) and I have had limited success so far. This is what the design looks like:
...
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Neutrinos from a Type 1a Supernova
How much energy does a Type Ia Supernova produce in the form of neutrinos?
I know that a Type II Supernova produces around $10^{45}$ joules worth of neutrinos, but not the amount produced by a Type 1a ...
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Will the universe be full of neutrinos?
If neutrinos are so easy to produce, but it rarely get absorbed or detected, doesn't that mean the universe will be full of neutrinos?
Will its density ever reach a balance where its absorption events ...
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Is Dirac neutrino ruled out by current experimental observation?
I have read the neutrino mass problem. The unnatural smallness of neutrino mass implies the existence of new physics so the seesaw mechanism is introduced to solve this theoretical problem.
I ...
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What happened in March 1991 when the IMB neutrino detector sprung a leak?
When I was in grad school, I recall hearing a story something like this:
"Once upon a time, there was a neutrino detector (Cherenkov water detector--just a large bag [in my memory of the story it ...
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$\beta^{+}$ and $\beta^{-}$ decay processes
We know that electron cannot exist inside the nucleus for various reasons like its energy, angular momentum violation and etc. But these $\beta^{+}$ and $\beta^{-}$ processes occurs inside the nuclei ...
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Why can't Dark matter be made up mostly of Neutrinos? [duplicate]
It's said that Neutirnos can only make up a tiny fraciton of dark matter.
So why can't Dark matter be mostly made up of Neutrinos?
Why can't there just be a huge number of them?
I suspect myself that ...
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Scatter angles at IceCube
Is it possible to have a scatter angle(in lab frame) to be greater than 90 degrees at IceCube, with this I mean the relative angle between the incoming (muon) neutrino and the outgoing (muon)lepton.
$$...
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How do the different Neutrino masses come about?
The determination of the Neutrino mass can be roughly divided in three strategies:
The neutrino mass from cosmological observations:
$$m_\nu = \sum_{i} m_i $$
The neutrino mass from the neutrinoless ...
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Has Anti-beta decay been observed?
I am looking for references or resources regarding the transition of an anti-neutron through weak decay, into an anti-proton, positron, and electron-neutrino.
Have such studies been conducted or ...
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Does neutrino oscillation imply that the lightest neutrino has mass? [duplicate]
If my understanding is correct, neutrino oscillation only implies that the neutrino families have different masses. People usually infer from this that all the masses are non-zero, but we can only ...
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Neutrino oscillations imply neutrino mass — Does the usual argument really hold?
An argument that people put forth is that because neutrinos can undergo changes in lepton flavor midflight, they must "experience time." Since massless particles must travel at the speed of ...
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Maximum energy of neutrino from decay of $W$ boson
Figure 2 of this paper suggests that neutrinos from the decay of on shell W bosons can have an energy as high as the W boson mass. However, in the $W^{-} \rightarrow e^{-} + \bar{\nu}_{e}$ process, ...
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(Basic) confusion about value of scalar-fermion vertex $\phi\psi_i\psi_j$ for Majorana fermions
If I have a toy model with $N$ Majorana fermions $\lbrace\psi_i\rbrace_{i=1,\ldots,N}$ and a scalar field $\phi$ where the interaction among the fields is
$$
\mathcal L_\text{int}= \sum_{i,j=1}^N
a_{...
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Dirac neutrinos?
How can Dirac neutrinos exist if neutrinos have no charge? As far as I'm aware, the antiparticle of a particle is its charge conjugate while all of its other characteristics remain same. How then can ...
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What is the control group in neutrino detection?
Assuming we can't block neutrinos, and most of them pass through the earth, how do we know that the change in the neutrino detector is not just happened randomly? Is the detection of neutrinos more ...
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Plotting the bipolar neutrino oscillations in supernova
everyone. I am trying to study the neutrino oscillation in a core collapse supernova. In certain situations neutrinos in supernova can undergo what is called a "bipolar" oscillation. ...
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What’s the most energetic particles that can theoretically reach the earth?
In recent years several ultra high energy cosmic ray events are observed on Earth. These particles carry energies way beyond even the most powerful particle accelerators we can realistically build. ...
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How can neutrinos be solely left-handed if they have mass?
Helicity: projection of spin onto motion. Since neutrinos are massive, I can always move to a reference frame where their motion is towards the opposite direction, meaning I should reverse their ...
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Clebsch-Gordon coefficients for isospin transformations
I'm trying to understand a paper in which the author uses the nuclear matrix elements from beta decay to arrive at the matrix elements for neutral-current neutrino-nucleus excitation. The author ...
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Why neutrino's mass states are assumed to share the same momentum?
In derivation of two-neutrino oscillation probability, it was assumed that the mass states have the same momentum. Why is that?
Source: https://www.youtube.com/watch?v=nXzur-2hbkI&t=115s&...
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Beta decay experiments suggesting that neutrinos are massless
It's known that in the kinetic energy spectra of electrons from the negative beta decays that at the end of the spectra some electrons are found to have a maximum energy that is equal to the energy ...
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How does neutrino free streaming length affect the growth of structures in the universe?
I cannot quite wrap my head around the exact mechanism by which neutrinos affect cosmic structure growth. Their effect as dark matter is clear to me but I don't understand how their longer free ...
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Does particle parity play any role in matter anti-matter annihilation?
If a left handed electron and a right handed antimatter electron were to meet, would they still annihilate?
In the same way, if a left handed electron and a left handed antimatter electron meet, will ...
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Why are accelerator beam neutrino experiments built an angle off the beam direction?
Was reading some papers and review articles on accelerator based neutrino experiments and this came up a few times. Most of what I could find mentions "shrinkage in neutrino energy spectra" ...
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How do we know that the neutrino flavour states are the linear combination of mass states?
I am studying the neutrino oscillation phenomenom in which the flavour of a neutrino can change when it evolves in space-time.
What I understand is that this means that the 3 neutrino flavour states ...
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Materials to Understand Energy loss of neutral charged particles such as Neutrinos?
I was reading about the energy loss of charged particles in matter and understood that the Bethe-Bloch equation governs the energy loss of charged particles interacting with matter. However I was ...
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How to construct a variational approach to finding the angle of a Neutrino beam?
I'm trying to construct a variational calculus approach to solving the angle at which a neutrino beam has to be fired through the earth, to hit a coin on the other side of the planet. For example, ...
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Majorana mass matrix seesaw and renormalizable interactions
Sometimes the general seesaw matrix:
$$\begin{pmatrix} M_L & M_1\\ M_2 & M_R \end{pmatrix}$$
and its just said that in order to get renormalizable interactions one must impose the condition $...
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Could we derive the mass of neutrinos using a supernova and gravitational lensing?
There are a lot of questions on this site about getting neutrino mass from timing the arrival of neutrinos vs light from a supernova, I believe this is different.
If we see a galaxy that is ...
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Do interactions slow down a particle? [closed]
I wonder whether particles, especially such as photons and neutrinos, do slow down when they interact in any way? E.g. how is it going on for the Compton effect but how is it in general like in QED or ...
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About Majorana neutrinos and chirality
If neutrinos are Majorana particles it is possible that neutrinoless double decay happens, with a diagram like this one:
However it seems to me that this diagram requires the Majorana neutrino to ...
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