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 there any experimental bounds on the ratio of neutrinos to antineutrinos in the universe?

In the Standard Model, both baryon number and lepton number are conserved quantities (excluding the theoretical possibility of sphaleron processes which are exceeding rare, at least at non-"near in ...
ohwilleke's user avatar
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Is it possible for quarks and charged leptons to 'oscillate' analogously to neutrinos?

In a hypothetical scenario where the coupling of the fermions to the gauge fields were extremely small, would it be possible to observe quark and charged leptons oscillate in the same manner as we ...
Eweler's user avatar
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Would a highly degenerate cosmic neutrino background affect fusion reactions that proceed via the weak interaction?

This might seem like a really strange question, but here's my reasoning. A proton-proton fusion reaction proceeds in two steps: \begin{align*} p + p + \text{1.25 MeV} &\rightarrow {}^2_2\mathrm{He}...
Thorondor's user avatar
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Sterile (4th) neutrino and cosmological bound

Recent results by MicroBoone seems to give support to old LSND experiment in favor of a fourth neutrino (sterile). How does it fit with the current cosmological bound for neutrinos?
riemannium's user avatar
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$2\nu\beta\beta$ vs. $2\nu$ECEC

Considering the recent observation of two-neutrino double electron capture ($2\nu$ECEC) by the XENON Experiment: https://arxiv.org/abs/1904.11002 I was wondering why the half-life of this process is ...
Katermickie's user avatar
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Do stellar model luminosities include neutrino losses?

I have had a sudden crisis in my understanding of the published outputs from stellar evolutionary model calculations. Usually these models output a "luminosity" that one can then use, along ...
ProfRob's user avatar
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Can antimatter form when a neutron absorbs a very high energy neutrino of the right flavor?

Art McDonald and Takaaki Kajita won the 2015 Nobel Prize in physics for discovering the oscillations between the 3 flavors of neutrinos; Electron, Muon, and Tau. This discovery showed that neutrinos ...
0tyranny0poverty's user avatar
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How to understand particle decoupling in the early universe?

We often say that when the rate of some interactions, say the beta decay and electron capture, are slower that the rate of universe's expansion, then the corresponding particles, say neutrinos, ...
Wein Eld's user avatar
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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 ...
seilgu's user avatar
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Zee QFT book on the neutrino mass

in p.102 of Zee QFT book, "As of this writing, it is not known whether the neutrino mass is Dirac or Majorana. We will see in chapter VII.7 that a Majorana mass for the neutrino arises naturally ...
ann marie cœur's user avatar
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Suppression of the mixing angle of the heavy neutrino in medium

Consider a fermion $N$ with mass $m_{N}$ and coupling to an active neutrino $\nu$ via the mixing $$ \mathcal{L} = m_{N}\theta \bar{N}\nu, $$ where $\theta\ll 1$ is the mixing angle. It is known that ...
Name YYY's user avatar
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Assumptions for Leptogenesis

In a video by Fermilab's YouTube channel "Can leptogenesis explain why there is something instead of nothing?", host Dr. Lincoln states four assumptions for the theory of leptogenesis. One of them is ...
MathTrain's user avatar
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Which Particle would win the race?

I have read this question: Neutrinos vs. Photons: Who wins the race across the galaxy? https://en.wikipedia.org/wiki/Neutrino And it made me curious. The wiki article says that neutrinos travel at ...
Árpád Szendrei's user avatar
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Why are neutrino flavour eigenstates expressed in terms of the elements of the complex conjugate of the PMNS matrix?

If we have $$ \begin{pmatrix} \nu_e\\ \nu_{\mu} \\ \nu_{\tau} \end{pmatrix} =\begin{pmatrix} U_{e1} & U_{e2} &...
stressed1767's user avatar
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Does the vacuum have a zero Seebeck coefficient?

I was considering how at very high energies (e.g the Schwinger Limit) the vacuum starts having properties we would normally associate with "materials", such as non-linear polarizibility. The Seebeck ...
Alex Meiburg's user avatar
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Does this physical situation distinguish whether you are viewing it a mirror?

The weak interaction's lack of $P$-symmetry is often explained by saying that "the amplitudes for processes involving the weak interaction are different from the amplitudes for the same processes ...
tparker's user avatar
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Is the right-handed antineutrino the CPT conjugate of the left-handed neutrino?

I am working from the book Massive Neutrinos in Physics and Astrophysics by Mohapatra and Pal (which is available here). On page 66, the authors claim that $\psi_{L}$ is the $\mathcal{CPT}$ conjugate ...
Kris's user avatar
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What're some criticisms of the paper "Six observations consistent with the electron neutrino being a tachyon with mass: mνe² = −0.11±0.016 eV²"?

Today I read about this paper making the case that neutrinos have imaginary mass and travel faster than light. I want to get excited, but I have no way to know how likely it is that this paper will be ...
akvadrako's user avatar
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Active-sterile mixing for KeVins

People sometimes talk about KeV mass sterile neutrinos as a warm dark matter candidate. I think they call them KeVins (horrible name btw). Now, In order for it to be a good dark matter candidate it ...
Dar's user avatar
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What happens when a neutrino and antineutrino meet?

My minimal knowledge of matter/animatter interaction is that only light is released and they obliviate each other. is this the same for neutrinos?
Justin's user avatar
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Why would it be (or it be not) valid to take that neutrinos can follow the same path as null geodesics?

Basically my main question is the one in the heading of my post, because apparently "Gravitation" by Misner, Thorne and Wheeler takes it directly as true and valid (a common place for null ...
omivela17's user avatar
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Why right-handed neutrino?

Interacting part of the $SU(2)_L$describing the Higgs and fermionic sector with one family $$\mathcal{L}= \bar{l}_Li\not Dl_L+\bar{e}_Ri\not\partial l_L+ \bar{\nu}_Ri\not\partial\nu_R - (y_{\nu}\bar{l}...
Monopole's user avatar
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Why is the scientific community, and especially the astrophysicists, so skeptical about sterile neutrinos?

As rob pointed out in a comment in my previous question : "There were hints about sterile or missing neutrinos in LSND, in the low-statistics region of MiniBoone, and in a number of other ...
Alfred's user avatar
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How was Potassium used to estimate the effect of backgrounds in the Homestake experiment?

I'm trying to understand some of the details of the Homestake experiment, which attempted to measure the rate of neutrino production by the sun. In particular, I'm interested in how Davis et. al. ...
Marcel Mazur's user avatar
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Neutrino Oscillation and FCNC

We know that in the Standard Model (SM) neutrinos are massless. But the discovery of neutrino oscillation suggests that neutrinos must have masses because only then there will be a mass basis for ...
Praveen Bharadwaj's user avatar
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Number and masses of right-handed neutrinos in the seesaw mechanism

In the Wikipedia article about the seesaw mechanism, it is argued that the seesaw mechanism "extends the Standard Model by assuming two or more additional right-handed neutrino fields", with ...
LCF2's user avatar
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Neutrino appearance and disappearance experiments

Why in neutrinos appearance experiments the background is said to be small? and how is it connected to the mixing angles? Why is it opposite in the neutrino disappearance experiments?
Arindam Mandal's user avatar
2 votes
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32 views

What is the difference between these mixing-angle equations?

In the following article the mixing angle of the neutrinos is given by: $$\sin^2 2\theta = \frac{\mu^2}{\mu^2 +[c\Gamma_\alpha E /M +M/2]^2} \tag{1}$$ where $\mu$ represents the Dirac mass , M ...
Geop's user avatar
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Why would the damping factor of neutrino oscillations be negligible?

In this article the Boltzmann equation for the sterile neutrinos is simpified to this form: $$\frac{\partial}{\partial t} f_s (p,t) -H p \frac{\partial}{\partial p} f_s (p,t) \approx \frac{\Gamma_\...
user7077252's user avatar
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1 answer
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What is a neutrino state if not a particle?

When reading about the 2015 Nobel prize and how this led to the possibility of the existence of sterile neutrinos I am told that: "(...) three active neutrinos $\nu_e$, $\nu_\mu$, $\nu_\tau$, are ...
user7077252's user avatar
2 votes
0 answers
206 views

What is the meaning of a Fermi blocking effect?

Given the Boltzmann equation: $$\frac{\partial}{\partial t} f_s (p,t) -H p \frac{\partial}{\partial p} f_s (p,t) \\ = \sum_i \int \Gamma_i (p'_\alpha ,p) f_\alpha (p'_\alpha , t) [ 1-f_s (p,t)]d^3 ...
user7077252's user avatar
2 votes
1 answer
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A search for IceCube events in the direction of ANITA neutrino candidates

In regards to the recent discover by ANITA of space-bound high energy Neutrinos, could this possibly be explained by atmospheric Beta Decay reactions producing these Neutrinos in between the IceCube ...
Raphaello's user avatar
2 votes
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What is the interpretation of a statistical CL contour *in the case* where the central observed measurement does not belong to the interior?

What is the interpretation of a statistical Confidence Level contour in the case where the central observed measurement does not belong to the interior of the contour ? (you may see below that this ...
Mathieu Krisztian's user avatar
2 votes
0 answers
72 views

Why potential energy of a non-relativistic particle in an expanding universe is $ma^2\phi$?

I have been reading a paper on neutrino clustering in an expanding universe: see section 3, particularly 3.3.2 of this paper. In this paper for non-relativistic neutrinos, which travel through a ...
fogof mylife's user avatar
2 votes
0 answers
87 views

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 ...
V. Nayak's user avatar
2 votes
0 answers
344 views

Why a neutrinoless double beta decay implies a massive neutrino?

I know neutrinos have mass thanks to the observation of the neutrino oscillations between one type to another (that cannot happen if they are massless particles because the mixing matrix will not ...
Juanjo's user avatar
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2 votes
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CP Phases in the PMNS Matrix

I am interested in how to derive the correct number of CP violating phases in the neutrino mixing matrix (or PMNS matrix). My approach is the following. By hypothesis, the neutrino mixing is given by ...
wnovelo's user avatar
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Neutrinos at the OPERA experiment

The probability that a neutrino oscillates from a species $a$ to a species $b$ is given by \begin{equation} P(a \to b) = \sin^2 (2 \theta_{ab}) \sin^2 \left( 1.27 \frac{\Delta m^2 L}{E_\nu} \right) \...
Sth99's user avatar
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2 votes
1 answer
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Role of the ratio L/E in neutrino experiments

Why is it that the neutrino experiments are designed by keeping constraints on the energy E of the neutrinos and the length L which they travel from the source to the detector. What decides actually ...
Seeker's user avatar
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2 votes
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185 views

How does heavy water detect all 3 flavors of neutrinos?

According to my understanding, scientists in Sudbury Canada and Japan were confused for a while on why they were getting only 1/3 of the expected neutrino capture from the sun. They then theorized ...
0tyranny0poverty's user avatar
2 votes
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103 views

Did electrons, right after the big bang, all had the same handedness (like all neutrinos are lefthanded)?

It is known that all neutrinos are lefthanded (for simplicity I don't discriminate between the technicalities of handedness and helicity), though in the answers of this question one can read that the ...
Deschele Schilder's user avatar
2 votes
0 answers
118 views

The stunning footage of neutral currents, first observation of a neutrino: Knowledge needed

First of all, this question is purely motivated by curiosity. I call upon the community's knowledge on the matter. Following the link below, you can see the image of "A lepton event - a neutrino ...
Golz's user avatar
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Using the boltzmann equation to find neutrino decoupling temperature

I'm an undergraduate student currently following a particle astrophysics lecture. I was reading some stuff about the neutrinos decoupling before the $e^+ e^-$ annihilations. It's possible to quickly ...
Indiana's user avatar
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2 votes
0 answers
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Is the left-handed neutrino, after seesaw, still the left-handed neutrino?

Reading this question and its answer Seesaw type-1 and integrating out heavy fields The diagonalization of the see-saw is described as going from "interaction basis" right (and left) handed ...
arivero's user avatar
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2 votes
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About the seesaw mechanism

I was reading about the seesaw mechanism in my Lecture notes and got a technical question. See for example http://www.lhep.unibe.ch/img/lectureslides/9_2007-11-30_SeeSawMechanism.pdf page 13. There ...
Prastt's user avatar
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How to get from angular velocity to acquired phase for neutrino oscillations in matter?

I am reading Akhmedovs 2000 paper on parametric resonance, and I cannot figure out the math of this particular passage: The difference of the neutrino eigenenergies in a matter of density $N_i$ is $...
Malte's user avatar
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Question on "new CNGS/OPERA measurement of neutrino velocity" (hep-ex/1212.1276)

A "new measurement of the limit on muon neutrino velocity with respect to the speed of light " by the OPERA neutrino experiment in collaboration with CERN has become public recently, as preprint http:/...
user12262's user avatar
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1 vote
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Within a generation, fermion species' mass seems like it could have an effect on how many of the fundamental forces it interacts with. Is this true?

So, fermions all interact with the gravitational force and the weak force. All fermion species. Now, if you eliminate from that list, the particles that don't interact with electromagnetism, you ...
blacktopshaman's user avatar
1 vote
0 answers
87 views

Determining the single particle energies in a neutrino opacity calculation

I'm attempting to recreate some plots from this paper on neutrino opacity calculations for interacting matter at supra-nuclear densities. Namely, I'm trying to write a Python script to perform the ...
10GeV's user avatar
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1 vote
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Does the neutrino take on different masses/energy/mometum in beta decay?

I am currently learning about quantum mechanics in my 12th grade Physics course and we're currently covering nuclear energy levels. I understand that alpha and gamma decay is discrete, as there is ...
jacob's user avatar
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