All Questions
15 questions
3
votes
1
answer
163
views
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
2
votes
1
answer
325
views
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
1
vote
0
answers
177
views
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
5
votes
4
answers
1k
views
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
6
votes
1
answer
201
views
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
2
votes
0
answers
79
views
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
0
votes
0
answers
85
views
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 ...
4
votes
1
answer
521
views
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
0
votes
0
answers
79
views
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)
$$
V_{CKM} =U_u^\dagger U_d = \begin{bmatrix} V_{ud} & V_{us} & V_{ub} \\V_{cd} & V_{cs} & V_{cb} \\
V_{...
- 4,376
0
votes
1
answer
39
views
Why does this distribution function depend on time and not temperature?
When reading Sterile neutrino hot, warm, and cold dark matter I came across the following momentum distribution function for a neutrino species $\alpha$:
$$\tag{5.8} f(p,t) = \frac{1}{e^{E(p)/T + \...
- 759
6
votes
2
answers
1k
views
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
2
votes
1
answer
528
views
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
vote
1
answer
116
views
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
2
votes
1
answer
165
views
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
1
vote
0
answers
71
views
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