All Questions
55
questions
2
votes
0
answers
35
views
General formula for a $f1\to f2$ gamma processes (e.g. $\mu \longrightarrow e\gamma$), understanding the detailed calculation in the paper by Lavoura
I want to work out in detail the paper by Lavoura to get some real practice as a beginning student. I have stumbled upon several problems as I am moving along with the arguments. Firstly, I am not yet ...
- 31
3
votes
1
answer
155
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
0
answers
118
views
Tadpole VEV from a fermion loop?
We have one extra complex scalar $\Phi$ beyond the Standard Model (BSM) protected by an $U(1)$ global symmetry, which is broken by an Yukawa coupling $ y_\Phi \Phi \overline{\chi} \chi$, where $\chi$ ...
- 21
1
vote
1
answer
263
views
Normalization of Kallen-Lehmann spectral representation, comparison to 4D spectrum from 5D theory
The Kallen–Lehmann spectral representation for a quantum field $\phi(x)$ is normalized:
$$\int_0^\infty d\mu^2\, \rho(\mu^2) = 1 \ ,$$
up to factors of $2\pi$ that are a matter of convention. See, for ...
- 1,198
4
votes
0
answers
75
views
Zee Chapter VII.5: Can the fermion $10$ be the composite of fermion $5^*$?
In Zee Chapter VII.5 QFT book:
He showed that the standard model fermions form $5^*$ and $10$ representations of $SU(5)$:
$$
5^* \oplus 10.
$$
In particular, the $10$ is the anti-symmetric matrix ...
- 4,336
5
votes
0
answers
94
views
Figure of $SO(10)$ grand unified theory in $E_6$ from Wikipedia
In this figure from Wikipedia, it shows that the representations of particles of $SO(10)$ grand unified theory, their patterns of charges for particles in the $SO(10)$ model, rotated to show the ...
- 4,336
4
votes
4
answers
411
views
Muon $g-2$ experiment: is there any theory to explain the results?
The nature of the experiment has been discussed here, but my main question is this: is there any theory that has predicted the results of this experiment or are we completely clueless about what's ...
46
votes
1
answer
2k
views
Resolving Conflicting Reports on Fermilab $g-2$ Results
Today it was announced that the Fermilab measurements of the muon's gyromagnetic ratio are in disagreement with the Standard Model with a statistical certainty reported at 4.2 sigma [1, 2], raising ...
- 3,710
2
votes
0
answers
104
views
CERN LHCb leptoquarks and grand unified theory
Recent CERN LHCb experiment suggests possible leptoquarks as new particles beyond the standard model may be discovered, with 3.1 $\sigma$ not the 5 $\sigma$ discovery.
What are the viable candidates ...
- 4,336
4
votes
1
answer
368
views
March 2021 CERN discovery? What would be the properties of the new particle/force from decaying bottom (beauty) quarks?
This question is directed mostly at people who are expert in (beyond) standard model(s) of elementary particles, but input by other physicists or students is very much appreciated.
A friend asked me ...
- 4,580
4
votes
2
answers
292
views
Breakthrough at the Large Hadron Collider -Leptoquarks skepticism?
I have came across this recent development in the LHC:
Breakthrough at the Large Hadron Collider: https://www.youtube.com/watch?v=qR6P0aRqYf8
Leptoquarks and leptons - quarks unification:
https://en....
- 4,170
2
votes
0
answers
87
views
Has the ${\cal N}=1$ Minimal SUSY standard model been ruled out by the nature? [duplicate]
Question: Has the ${\cal N}=1$ Minimal SUSY standard model (MSSM) been ruled out by the nature? What are the natural constraints that ruled out such ${\cal N}=1$ MSSM?
In particular, the ${\cal N}=1$...
- 4,336
1
vote
1
answer
883
views
Terminology about chiral supermultiplet and vector supermultiplet
I have an issue with the terminology about chiral supermultiplet and vector supermultiplet.
In the Pierre Ramond's Journeys Beyond The Standard Model p.286, he used the phrase
chiral vector multiplet ...
- 4,336
1
vote
1
answer
265
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) ...
- 4,336
3
votes
2
answers
253
views
Proton decays in Pati-Salam model or Georgi-Glashow model
This Pati-Salam model doesn't predict gauge mediated proton decay, according to Wikipedia.
However the Georgi-Glashow model predict gauge mediated proton decay, according to Wikipedia.
I thought the ...
- 4,336