All Questions
Tagged with neutrinos quantum-field-theory
73 questions
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64
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Deriving the EFT from a Lagrangian with a Right-Handed Neutrino Field
I am working through the MIT EFT course, and I am having trouble with one of the problems. The task is to find the effective field theory (EFT) from the most general Lagrangian with a right-handed ...
- 332
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0
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40
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Calculations Regarding Neutrino Self-Interaction
I have recently been looking at papers talking about neutrino self-interactions and have seen quite different results among papers. One considers the addition of ${\mathcal{L}} \supset \frac{\lambda_{\...
- 291
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1
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73
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Where is antineutrino in standard model Lagrangian?
I'm somewhat confused by the content I studied in Srednicki's work, where the neutrino is described as a Majorana field. In this framework, there shouldn't technically be antineutrinos, given the ...
- 631
3
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1
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163
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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 ...
- 71
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1
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97
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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
$$
\mathcal L_\text{int}= \sum_{i,j=1}^N
a_{...
- 277
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1
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129
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How do we know that the neutrino flavour states are the linear combination of mass states?
I am studying the neutrino oscillation phenomenom in which the flavour of a neutrino can change when it evolves in space-time.
What I understand is that this means that the 3 neutrino flavour states ...
- 21
1
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1
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89
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Flavor Oscillations, the case of leptons
In the neutrino sector neutral particle oscillation occurs which gives rise to neutrino oscillation. From my currrent understanding , the observation of the neutrino oscillation occurred because the ...
- 585
1
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1
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206
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$\nu_e \bar{\nu_e} \rightarrow e^- e^+$ confusion
Interacting part of the $SU(2)_L$describing the Higgs and fermionic sector with one family
$$\mathcal{L}= \bar{l}_Li\not Dl_L+\bar{e}_Ri\not\partial e_R+ \bar{\nu}_Ri\not\partial\nu_R - (y_{\nu}\bar{l}...
- 3,494
6
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1
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313
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Does the neutrino interact with the photon?
I know that the straight answer is no, but in my EFT course, where we're interested in nonrenormalizable operators of the Lagrangian, things aren't so straightforward.
The non-minimal QED Lagrangian ...
- 6,049
3
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1
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580
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$Z$-boson decay into two neutrinos depends on the Dirac or Majorana nature of the neutrinos?
The decay rate of the $Z$-boson into two active neutrinos $Z \rightarrow \nu \overline{\nu}$ can be calculated straightforwardly and I obtained the same as in the literature. However, I was wondering, ...
- 49
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172
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Fermi's theory and left-handed anti-neutrino
I calculated the $\mu \rightarrow e^- + \nu_{\mu} + \bar{\nu}_{e}$ both in Fermi's theory (V-A) and Intermediate Vector Boson theory and IVB at first order seems to match with Fermi's theory which is ...
- 3,494
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0
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36
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Finite distance propagation for charged particles
Usually, when it comes to studying QFT at a finite distance, the underlying problem is neutrino oscillations. Could it be relevant in some sense to study finite-distance propagation of charged ...
2
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0
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79
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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 ...
- 95
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1
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135
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Photon - Neutrino interaction
Suppose we have a laser source, that means a coherent laser beam formed by 'in phase' photons. Is it possible to calculate how many photons can change their wavelength in neutrino - photon interaction ...
- 603
2
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1
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325
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The neutrinoless double beta decay can only occur if $\dots$
In Wikipedia https://en.wikipedia.org/wiki/Neutrinoless_double_beta_decay#Overview
it says that
The neutrinoless double beta decay can only occur if
(1) the neutrino particle is Majorana, and
(2) ...
- 4,376
3
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80
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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 ...
- 4,376
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79
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CP violation phases counting in neutrino flavor mixing sector with $N$ sterile neutrinos
In the quark sector, the CKM matrix is obtained from (see p.723 of Peskin QFT)
$$
V_{CKM} =U_u^\dagger U_d = \begin{bmatrix} V_{ud} & V_{us} & V_{ub} \\V_{cd} & V_{cs} & V_{cb} \\
V_{...
- 4,376
0
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0
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85
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Flavor mixing Higgs Yukawa term with both left and right chiral neutrinos and with generic masses
In p.727 of Peskin QFT, it derives a flavor mixing Higgs Yukawa term, but he assumes that the neutrinos have no mass.
However we know that we can include both left and right chiral neutrinos, and also ...
1
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0
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71
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Derivation of matter potential from QFT
I'm trying to derive the matter potential as experienced by neutrinos from QFT. The paper I am looking at is unfortunately not publicly available online (https://doi.org/10.1103/PhysRevD.40.259) and ...
- 357
1
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177
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How to give left-handed neutrinos alone Majorana mass?
The Wikipedia page on Georgi–Glashow model says
Fermions transforming as a 1 under SU(5) are now thought to be necessary because of the evidence for neutrino oscillations, unless a way is found to ...
- 4,376
0
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1
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39
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Why does this distribution function depend on time and not temperature?
When reading Sterile neutrino hot, warm, and cold dark matter I came across the following momentum distribution function for a neutrino species $\alpha$:
$$\tag{5.8} f(p,t) = \frac{1}{e^{E(p)/T + \...
- 759
3
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0
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30
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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 ...
- 8,971
6
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1
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201
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Does our failure to detect neutrinoless double beta decay spell trouble for the seesaw mechanism?
The seesaw mechanism is a theoretical model of neutrino masses that has the side benefit of (arguably) naturally explaining why neutrinos are so much lighter than the other massive Standard Model ...
- 49.4k
21
votes
3
answers
4k
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Why do people say that neutrinos are either Dirac or Majorana fermions?
The question of whether a given particle "is" a Dirac or Majorana fermion is more subtle than is sometimes presented. For example, if we just consider the "old" Standard Model with massless neutrinos, ...
- 49.4k
1
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1
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135
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Interaction of neutrinos with matter
I am an undergraduate student working on a project on neutrino oscillations. I am currently trying to code the probability of neutrino oscillations in matter (MSW effect). I am using the following ...
- 13
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0
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63
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How to describe the interaction between a neutrino and a nucleus?
I know the basics of particle physics and QFT.
How do you write it down the interaction between a a neutrino and an atomic nucleus (or many of them)? what equation or Lagrangian or anything else do ...
- 1,171
1
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0
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48
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Neutrino oscillations in Cheng and Li
Cheng & Li's Gauge theory of elementary particle physics has the following formula for the average intensity of neutrino oscillations (Eqs 13.30 and 13.31) on p 411.
\begin{align}
\langle P_{\nu_e\...
- 3,165
7
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1
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914
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Is $CP$ instead of $C$ 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-...
- 27.2k
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0
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90
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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 ...
- 935
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1
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137
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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 ...
- 99
2
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2
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827
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When considering a general mass term with Majorana masses, how do you exclude the existence of the left-handed neutrino mass?
Considering a general mass term describing the neutrino masses:
$$
-\frac{1}{2}
\begin{pmatrix}
\bar\nu_{R} & \bar\nu_L
\end{pmatrix}
\begin{pmatrix}
M_R & m \\
m & M_L
\end{pmatrix}
\...
- 1,373
3
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3
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337
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Weak interaction of $(\nu^c)_R$ fields of the SM and $N_R$ fields in type-I seesaw extension of the SM
The antiparticle of $\nu_L$ is given by its charge conjugated field i.e., $(\nu_L)^c$ which is equal to $(\nu^c)_R$. Both $\nu_L$ and $(\nu^c)_R$ are part of the Standard Model (SM) of massless ...
- 27.2k
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234
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Time evolution of a massive fermion produced in a state of definite chirality
But for massive particles like an electron, the chirality is not conserved in time i.e. if an electron is produced in the state $e_L$ at time t=0, at a later time it becomes a mixture of left-handed ...
- 27.2k
2
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1
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528
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How can we calculate the PMNS matrix in general?
If we only introduce Dirac mass terms for neutrinos, we have analogous to the quark mass matrices, a normal $3 \times 3$ neutrino mass matrix $M_\nu$, written in the basis: $(\nu_L^1,\nu_L^2,\nu_L^3)...
- 10.3k
1
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2
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358
views
Matter effects in neutrino oscillation
The neutrino oscillation probability in matter is given as:
where
Now what I do not understand is that "As the energy increases, the probability
of oscillation within the sun through the matter ...
- 760
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0
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215
views
Mass of a Dirac neutrino
(I have restated the question after the comments to make it clearer)
Is there any way mathematically a Dirac neutrino can have different mass for LH and RH state?
The dirac mass term (obtained after ...
- 760
1
vote
2
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187
views
Comparison between two flavor neutrino oscillation and a system of up-spin and down-spin states of an electron?
In the system of up-spin and down-spin states of an electron, we can write a general state of electron at time $t$ as
$$\left|\psi(t)\right>=a\left|\uparrow\right>+b\left|\downarrow\right>,$$...
- 105
1
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0
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71
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Is it possible that are particle is much heavier through a loop correction?
Let's assume, we have standard model singlet particle $s$, that mixes after electroweak symmetry breaking with an exotic, vectorlike neutral lepton $N$. The relevant part of the Lagrangian reads
$$ L ...
- 10.3k
2
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1
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165
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Why are the radiatively generated neutrino masses finite?
In the Zee model and the Ma model of radiative neutrino masses, a naturally small neutrino mass is generated at the one-loop level. But loop diagrams are generally divergent. There is no mass at the ...
- 27.2k
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3
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76
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Could neutrino oscillations be due to exchange of gamma rays?
I was wondering since the relativistic mass-energy of a gamma ray photon is 1.24 MeV/c^2 and the mass of an electron neutrino is < 2.2 eV/c^2 whether the oscillations between the two could, in the ...
- 1,562
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2
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1k
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Can a Majorana field $\psi$ be charged under some $U(1)$ with a charge other than zero?
I know Majorana particles have to be electrically neutral because electric charged is conserved.
My question, however, is whether at all a Majorana field $\psi$ be charged under any $U(1)$ (other ...
- 27.2k
0
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0
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298
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From interaction Lagrangian density to scattering amplitude
I'm currently working on coherent elastic neutrino nucleus scattering (CE$\nu$NS) and have been trying to find out how to obtain the cross section mentioned in all the papers. Unfortunately, it is ...
1
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1
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116
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Can the Mikheyev-Smirnov-Wolfenstein (MSW) effect be modified by non-standard neutrino-neutrino interactions?
The MSW effect describes how propagation of neutrinos through matter can resonantly enhance the neutrino mixing. The reason for this enhancement is that the presence of electrons in matter changes the ...
- 1,803
7
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1
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954
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Which Standard Model Constants have beta functions?
Background
The Standard Model of Particle Physics has 26 experimentally measured parameters specific to the model (excluding physical constants like the speed of light that have applications outside ...
- 3,967
4
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1
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521
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Flavour symmetries of neutrino and charged lepton mass matrices
The symmetry of neutrino mass matrix $M_\nu$ is often realized as $$G^TM_\nu G=M_\nu$$ where $G$ is an element of the corresponding symmetry group. Is this because the neutrinos are Majorana in nature?...
- 27.2k
3
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1
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185
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Why is the beta emission in Wu's Experiment always in one direction but not the other?
I am learning the parity violation. In Wu's experiment, the electrons tend to emit always opposite to the direction of the electromagnetic field. My confusions are:
1.Why not the other way?
2.Does ...
- 1,071
16
votes
2
answers
3k
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If the mass of neutrino is not zero, why we cannot find right-handed neutrinos and left-handed anti-neutrinos?
I am learning P&S's Introduction of quantum field theory. My teacher said that if the mass of neutrino is exactly 0, then we should not observe any right-handed neutrinos and left-handed anti-...
- 1,071
1
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0
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150
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What is longitudinal nature of Neutrino waves?
I was reading about the Neutrino Theory of Light (just for its learning value, I know it is not accepted that much these days), I came to a sentence in Wikipedia that was comparing light with neutrino ...
- 291
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4
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1k
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Calculating the $\mu\rightarrow e\gamma$ decay and cancellation between diagrams
In the book “Gauge theory of elementary particles-Cheng and Li, section 13.3, the $\mu\rightarrow e\gamma$ decay amplitude is calculated in the $R_{\xi}$ gauge. Regarding this derivation, I'm stuck ...
- 27.2k
1
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0
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44
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Influence of matter of a star on masses of neutrinos
It is well known that if neutrinos has masses then from Dirac equation it follows that they propagate (in vacuum) as a eigenstates of mass (not as eigenstates of interaction). It's wave function is of ...
- 512