Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [neutrinos]

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

1
vote
0answers
22 views

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 ...
2
votes
1answer
44 views

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 ...
0
votes
0answers
23 views

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 ...
1
vote
1answer
31 views

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 ...
1
vote
1answer
21 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 ...
1
vote
1answer
71 views

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 ...
0
votes
0answers
32 views

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 $(-1)$. ...
4
votes
2answers
133 views

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 ...
0
votes
1answer
52 views

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 ...
2
votes
1answer
40 views

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 ...
3
votes
2answers
46 views

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 ...
0
votes
1answer
54 views

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 ...
4
votes
1answer
57 views

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 ...
0
votes
2answers
34 views

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 ...
1
vote
0answers
31 views

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{...
2
votes
1answer
104 views

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 ...
0
votes
1answer
45 views

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 ...
5
votes
1answer
161 views

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-...
0
votes
0answers
16 views

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 ...
0
votes
1answer
22 views

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 ...
-3
votes
1answer
152 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?...
1
vote
0answers
31 views

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(...
1
vote
2answers
88 views

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 ...
3
votes
1answer
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) ...
0
votes
1answer
25 views

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 ...
1
vote
2answers
120 views

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), ...
1
vote
0answers
32 views

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 ...
1
vote
1answer
52 views

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 ...
2
votes
1answer
165 views

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 ...
0
votes
1answer
51 views

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 ...
0
votes
1answer
49 views

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?
1
vote
1answer
48 views

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 ...
4
votes
2answers
75 views

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, ...
4
votes
1answer
55 views

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 ...
3
votes
1answer
64 views

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 $$\...
2
votes
1answer
66 views

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 ...
0
votes
1answer
51 views

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?
3
votes
2answers
91 views

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 ...
3
votes
1answer
398 views

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., ...
2
votes
1answer
135 views

What's up with these new high energy neutrinos?

A bunch of pop science articles just popped up talking about new high-energy neutrino detection. See this article, published today, for example. The answer to this question says that the source of ...
2
votes
1answer
144 views

Could neutrinos be tiny black holes? [closed]

I think about this because neutrinos only interact with gravity. The Schwarzschild radius is directly proportional to the mass and does not prevent values that tend to zero. There seems to be no ...
18
votes
4answers
4k views

Neutrinos passing through black hole

I have read this: https://en.wikipedia.org/wiki/Neutrino The weak force has a very short range, gravity is extremely weak on the subatomic scale, and neutrinos, as leptons, do not participate in ...
1
vote
0answers
70 views

Gravitons passing through matter like neutrinos

I have read these : https://en.wikipedia.org/wiki/Graviton https://en.wikipedia.org/wiki/Neutrino where it says: The weak force has a very short range, gravity is extremely weak on the subatomic ...
0
votes
0answers
38 views

What are the higher order Feynman diagrams I have to consider in muon neutrino-electron scattering?

I think in a $\nu_\mu + e^{-}$ scattering can happen: $\nu_\mu + e^{-} \rightarrow \mu^{-} + \nu_e$ and $\nu_\mu + e^{-} \rightarrow \nu_\mu + e^{-}$ With two Feynman diagrams (CC and NC). My ...
4
votes
0answers
44 views

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?
2
votes
1answer
71 views

If $U$ determines the mixing between fields and $U^*$ determines the mixing between states-Why?

In this pdg review, Eq. (14.1), the mixing between the flavour neutrino fields and neutrino fields corresponding to mass eigenstates are denoted as $$\nu_{lL}=\sum\limits_{j}U_{lj}\nu_{jL}\tag{1}$$ ...
1
vote
1answer
62 views

Would the universe be significantly different if neutrinos were massless?

As far as I know, neutrino oscillation experiments have fairly conclusively demonstrated that neutrino states have mass. However, neutrinos are so frequently taken to be massless in cosmology that I ...
1
vote
0answers
68 views

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 ...
2
votes
2answers
139 views

Neutrino flavor change in flight

I have read this article: https://profmattstrassler.com/articles-and-posts/particle-physics-basics/neutrinos/neutrino-types-and-neutrino-oscillations/velocity-differences-of-neutrinos/ https://en....
2
votes
1answer
70 views

What distinguishes the behaviour of particle from its antiparticle: C violation or CP violation?

It is said that a CP violation would mean that the behaviour of the particle is different from the behaviour of antiparticle. Why is C violation not good/enough?