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 [beyond-the-standard-model]

Use this tag for questions beyond the standard laws of physics (General Relativity and the Standard Model) if a more specific tag, like "string-theory", "loop-quantum-gravity", "supersymmetry", etc. do not apply.

0
votes
0answers
21 views

Latest SUSY limits from LHC [on hold]

What are the latest limits on low energy supersymmetry scale from experiments (LHC, etc.)?
1
vote
0answers
33 views

How does Alain Connes NCG compare phenomenologically with superstring theory?

In Veltmans book on QFT, diagrammatica, the full SM Lagrangian is published. There are more than a hundred terms and it looks pretty uninspiring and not quite the kind of equation one would want to ...
1
vote
0answers
27 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 ...
0
votes
0answers
32 views

Where can I find the detailed calculation for the mass of the lights Higgs boson in MSSM?

can somebody mention where the mass of the lights Higgs boson in MSSM (minimal supersymmetric standard model) is discussed? I need a detailed and thorough explanation of the subject mater. I ...
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
33 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 ...
3
votes
1answer
96 views

Is anything expected to be found at CERN with 14 trillion electron volts that wasn't found at 13?

Based on this article the accelerator has smashed together approximately 16 million billion protons since 2015, when it reached its current energy of 13 trillion electron volts. Planned ...
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 ...
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
82 views

Could there be elementary particles with electric charge $> 2e$?

There are many quantum field theories, which extend the Standard Model and have new particles. For example, X boson of Georgi-Glashow model has charge $4e/3$ and some Higgs models involve a Higgs ...
1
vote
1answer
56 views

Constraints on RH component of fermion triplet under $SU(2)_L$

Consider a fermion $\chi$ whose left-handed part is in a triplet representation of $SU(2)_L$: $$ \chi_{L} = (\chi^1,\chi^2,\chi^3)_L^{\ \ \text{T}}. $$ The charged current of $\chi_L$ (i.e. its ...
0
votes
1answer
74 views

Can $E_8 \times E_8$ contain the standard model?

I know $E_8$ by itself can't be gauge group because it has no complex representation and so would not be chiral. But assuming the existence of mirror matter which also would have $E_8$ gauge group ...
-1
votes
1answer
62 views

Emergent physics in the gap between the Planck scale and the “size” of quarks [closed]

The smallest probed length scale to date is around $\Delta x \approx 10^{-18} m$ (see here). If we compare this to the Planck scale of $\Delta x \approx 10^{-35} m$ we are left with almost 20 orders ...
4
votes
1answer
58 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
0answers
11 views

Inclusive vs exclusive br fractions

Consider the inclusive process $$ q \to X, $$ where $q$ is the quark inside some hadron $H$, and $X$ is some fixed final state. Corresponding exclusive processes are $$ H \to X_{1}, \quad H \to X_{...
0
votes
1answer
27 views

Can the CKM matrix supply the CP asymmetry as required by baryogenesis, in principle?

In the process of Baryogenesis through Leptogenesis from the decay of heavy Majorana neutrinos, the necessary CP violation is perhaps provided only by the CP phases in the PMNS matrix. But the Weak ...
1
vote
3answers
255 views

Given the transformation of $SU(2)$ triplet $\vec{\phi}$ how to find the transformation of ${\Phi}\equiv\vec{\phi}\cdot\vec{\tau}$?

Given the transformation of a $SU(2)$ triplet $\vec\phi$ $$\phi\to \exp{(-i\vec{T}\cdot\vec{\theta})}~\vec\phi\tag{1}$$ (in the question here by @physicslover) how does obtain the transformation of $\...
1
vote
1answer
67 views

Like the Higgs sector of the standard model, is there a SUSY sector which is also such a sector?

This question arose from an application of the virial theorem that showed how Bose-Einstein condensates of astrophysical dimension could arise from condensing clouds of normal phase bosons. If these ...
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) ...
8
votes
1answer
224 views

Why should proton decay into positron rather than antimuon?

Grand unification theories, such as $SU(5)$/$SO(10)$/SUSY variants, suggest proton decay. The lack of observational evidence for proton decay rules out simple GUTs. But wait a minute! The GUT's ...
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), ...
10
votes
1answer
640 views

Why does only gravity leak into extra non-compact dimensions?

This article K. Pardo, et. al., Limits on the number of spacetime dimensions from GW170817, Journal of Cosmology and Astroparticle Physics, Vol. 2018, 2018. which was published recently in JCAP ...
0
votes
1answer
62 views

Higgs Doublet Transformations

If we consider two complex Higgs doublets with $SU(3)_{c} ⊗ SU(2)_L ⊗ U(1)_Y$ quantum numbers $\phi_{A,B}$ ∼ (1,2,1), such that $\phi_A = \begin{pmatrix} \phi_{A}^{\dagger}\\ \dfrac{1}{\sqrt2} (Re \...
0
votes
1answer
52 views

Unification of the strong and electromagnetic interaction

Is it somehow possible to theoretically unify the electric charge in electromagnetic interaction with the colour charge in the strong interaction and how these charges give rise to the respective ...
0
votes
0answers
41 views

3 generations as extra unconventional dimensions?

Kaluza-Klein resonances arise in theories with extra dimensions like superstrings or old KK models. Usually, extra dimensions and KK states provide regular spacing in the spectrum. Question: can some ...
0
votes
0answers
82 views

Dark Matter Monojet signal

Dark matter can be observed at the LHC via a mono-jet signal i.e $pp\rightarrow XX + jet$. These signals can proceed via parton level processes like the mono gluon or mono photon ones. I was ...
8
votes
1answer
189 views

Why is technical naturalness enough?

There are two notions of "naturalness" used in particle physics today. Dirac naturalness: all dimensionless parameters $g$ in a theory should be order $1$. Technical naturalness: an observed coupling ...
1
vote
0answers
47 views

What is the status of SUSY GUTs in 2018?

Grand unification theories (GUTs) generically predict proton decay, and many of them have been under pressure for decades as experiments have failed to see it. I don't think there have been recent ...
3
votes
0answers
41 views

Are trans-Planckian field values a problem for the relaxion?

The relaxion is a new model-building gadget that solves the hierarchy problem by allowing the Higgs mass term to dynamically relax to zero. To describe it as simply as possible, leaving a lot out: we ...
10
votes
0answers
236 views

What motivates clockwork theory?

Clockwork is a new model-building gadget that produces very small couplings starting from a theory with no small numbers at all, in an attempt to solve the hierarchy problem. To describe it as ...
2
votes
1answer
72 views

U(1) Dirac string moved to the SU(2) or SO(3) gauge theory

Dirac string describes the string connecting the U(1) magnetic monopole to the U(1) anti-magnetic monopole in the U(1) gauge theory. Since U(1) is a subgroup of SU(2) and SO(3), we may embed the U(1) ...
0
votes
0answers
16 views

Computing hadronic cross sections with PDFs

I am trying to estimate the cross section for a BSM process at the LHC, and I would like to ask if anyone knows what is the simplest way to integrate over the PDFs, for example with Mathematica. I ...
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?
1
vote
1answer
87 views
0
votes
1answer
116 views

Does the sedenion algebra offer a grand unification theory?

Stephane Bronoff in The Standard Model of Particle Physics from Sedenions claims that studying the left-multiplication map of unit doubly-pure sedenions solves several mysteries of the standard model. ...
3
votes
1answer
139 views

Why is the dark matter freeze-out temperature $T\sim \frac{m}{20}$ so generic?

For a dark matter of mass $m$, the typical freeze-out temperature is $T$ is usually assumed to be between $\frac{m}{20}-\frac{m}{25}$. But the freeze-out temperature depends upon the annihilation ...
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 $$\nu_{lL}=\sum\limits_{j}U_{lj}\nu_{jL}\tag{1}$$ ...
2
votes
1answer
47 views

Is it sufficient to consider the uncharged dark matter and a $\mathbb{Z}_2$ symmetry to prevent its decay into photons?

Higgs boson, though electrically neutral, can decay to produce a pair of photons i.e., have electromagnetic interactions. See the answer here. Therefore, it appears that making dark matter ...
0
votes
1answer
86 views

Why can't the Higgs vacuum energy clump to galaxies and act as dark matter (instead of dark energy)? [closed]

The Higgs field has a nonzero vacuum expectation value which contributes to the energy density of the Universe. Energies contribute to the curvature of spacetime and affected by gravitational ...
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?
2
votes
2answers
103 views

Why is it assumed supersymmetry in nature is ${\cal N}=1$?

It is often presumed that if supersymmetry exists then there will be a single supersymmetry (${\cal N}=1$). Why do we assume this? What is wrong with additional supersymmetries (${\cal N}>1$)? For ...
17
votes
3answers
3k views

What gives mass to dark matter particles?

Assuming that dark matter is not made of WIMPs (weakly interacting massive particles), but interacts only gravitationally, what would be the possible mechanism giving mass to dark matter particles? If ...
0
votes
0answers
51 views

Regarding R-symmetry in SUSY algebra - III

This is a follow up to my previous questions, this and this. In $N = 1$ SUSY, we introduce $R$-parity (or matter parity) so as to write down interaction terms in Lagrangian involving chiral ...
2
votes
0answers
29 views

Hadrons in realistic string phenomenology

String theory contains a number of models of baryons as branes, notably the Sakai-Sugimoto model. But I don't remember ever seeing a discussion of baryons, or any kind of hadron, in the specific ...
1
vote
1answer
83 views

Why does Kaluza-Klein theory or the Randall-Sundrum model propose only one extra dimension?

Reading popular accounts on string theory, I have the impression that the number of extra dimensions of string theory is not an ad hoc postulate; it's uniquely determined by mathematical consistency. ...
2
votes
1answer
100 views

Which extensions of the Standard model have the inflaton candidates?

Like dark matter and dark energy, there is no candidate of inflaton in the Standard Model (SM) of the particle physics but its various extension does have candidates of dark matter. Does the minimal ...
0
votes
0answers
29 views

About the experimental measurement of neutrino magnetic moment and its value

Massive neutrinos, be it Dirac or majorana, have magnetic moment. See here, here and here. $\bullet$ How is it measured (or can be measured) in real experiments? What are the (upper and lower) ...
3
votes
0answers
275 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 ...
0
votes
0answers
44 views

The Higgs boson mass, the Higgs self-coupling and SUSY

How can the measured Higgs boson mass, about 125GeV, and the future measurement of Higgs self-coupling affect to the existence of low/medium/high energy SUSY? I mean, is there a way in which these 2 ...