Questions tagged [standard-model]

A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong and weak nuclear forces (and the Higgs mechanism). Do NOT use this tag for the standard model of cosmology, etc..

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Has anyone made a objection to fluid sink model? [closed]

Poincares objection is here (WaybackMachine), the Wikipedia objections are terrible, has anyone made any actual objection to Le Sage theory? Not defending it or anything just wondering why Wikipedia ...
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Brans-Dicke's model : how to shift to the left the curve of scale factor to get a standard age for universe?

Using a code that implements the Brans-Dicke's model with all the modified equations of field. By doing MCMC, I have found the following estimations : $\Omega_m=0.240303,\\ \Omega_{de}=0.761206,\\ \...
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Do Higgs fields commute with $W^1$, $W^2$, $W^3$, $B$, and why?

In Standard Mode, we have quantities such as : $\left(D_{\mu}\Phi\right)= \left( \begin{array}{cc} \partial_{\mu}+i\frac{g}{2}W_{\mu}^3+i\frac{g'}{2}B_{\mu} &i\frac{g}{2}W_{\mu}^1+\frac{g}{2}W_{\...
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Is CPT symmetry an accidental symmetry?

Since $\mathcal{CPT}$ is a direct consequence of the Special Relativity, is it considered an accidental symmetry of the Standard Model?
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Is CPT symmetry a direct consequence of Special Relativity?

I'm wondering about the origin of $\mathcal{CPT}$ symmetry in the Standard Model. The Wikipedia entrance makes me understand it is a direct consequence of Special Relativity. Is it right?
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How (if) are the Higgs scalar and the $W/Z$ vectors related (apart from interaction)?

An idea popped up in my mind. There are three vector bosons, the two charged $W$-particles, and the $Z$-particle, all three with spin 1. Is the Higgs particle, having spin 0, related to them, apart ...
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How is the interaction of leptons and quarks with gauge fields organized in the Standard Model?

Well, standard model has $SU(3)\times SU(2)\times U(1)$ gauge group, so this is a direct product of multiple groups embedded in larger set. So how quarks that must interact with every gauge field and ...
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How do we know that the gluon travels at $c$? [duplicate]

How do we know gluons travel at the speed of light? can this be derived or is it just an assumption based on the similarity to photons?
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What are the symmetries of standard model and its conservation laws? [closed]

Is there like a list of symmetries in the standard model with associated conservation laws?
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Energy and Momentum conservation in Bhabha scattering

I came across this question here which was asking my exact initial question (I even came from Griffiths problem 2.4 too!). But the given answer gave me a lot more questions which I think constitute ...
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What is wrong with the dependence of result with the order of the operation in my computation of Higgs sector derivative term?

In Standard Model Higgs sector, there are terms that introduce : $\left(D_{\mu}\Phi\right)= \left( \begin{array}{cc} \partial_{\mu}+i\frac{g}{2}W_{\mu}^3+i\frac{g'}{2}B_{\mu} &i\frac{g}{2}W_{\mu}^...
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Kinetic energy of quarks and mass of proton

I read that: Most of a proton mass comes from the energy of motion of its three quarks and from the energy carried by the gluons that keeps them confined together. Does kinetic energy of the three ...
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What are the numerical values of the gauge coupling constants? [duplicate]

I mean the values of: $U(1)$ gauge coupling $SU(2)$ gauge coupling $SU(3)$ gauge coupling
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Vacuum Transitions and Lorentz Symmetry Breaking

There are many "bumblebee" models 1, 2 where Lorentz invariance is violated usually resulting from a local vector or tensor field acquiring a nonzero vacuum expectation value We do not know ...
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Is there a law stating why a quark never decays weakly into a quark of the same weak-isospin ($T_3$)?

So I read multiple articles on weak isospin and one of them stated that "a quark never decays weakly into a quark of the same $T_3$". If this is true, can someone please explain what law ...
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$\rho$ and $\omega$ mesons decays

As far as I understand, typical decay for $\omega$ meson is into $3\pi$, while for $\rho^0$ is into $2\pi$. In fact they are quite similar particles (same spin, parity, similar masses). Why this ...
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Why does the Strange Quark have Strangeness -1?

I have been trying to find an explanation for the strange quarks negative strangeness value, I understand the term strangeness predates the quark model, but I'm unsure if terminology carry over is the ...
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Is Lepton Flavour Universality an accidental symmetry of the Standatd Model?

Is Lepton Flavour Universality an accidental symmetry of the Standatd Model? If it is, why? How does it emerge from the Standard Model?
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What does it mean for the $\textbf{B}$-field (Hypercharge) to be in the 0 representation within the SM?

I was reading through the wikipedia page for the mathematical formulation of the standard model and I noticed that it listed the representations of the vector bosons under the SM gauge groups as being ...
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Does the Higgs field have an energy?

I have many questions about the notion of space. I learned that at the quantum level, energy became quantized and that the infinite sum of energy states can no longer be substitued by integrals (...
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What boundary/initial values should one take for running the couplings in the Standard Model?

(This is a very naive question!) I am trying to run the Standard Model(SM) couplings at 2-Loop, which includes three gauge couplings, Yukawa couplings, and Higgs quartic coupling. This requires me to ...
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How do you deal with particle interaction amplitudes which contain projection operators?

From a Feynman diagram I have written down the matrix element. It is for a decay: $$ P_{L}[u(k)] \rightarrow \bar{u}(p_{1}) + Z^{*} \rightarrow \bar{u}(p_{1}) + \bar{u}(p_{2}) + P_{L}[v(p_{3})] $$ ...
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Even if the Standard Model was found to be complete and in a stable vacuum, could a transition into a false vacua and then decaying change it?

In theory (please correct me if I am wrong in any point), if our vacuum were metastable (i.e. in a "false vacuum" state), it could go through a phase transition into a stable state (a "...
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What is the lagrangian interaction term of a charged current weak interaction?

For example, if you have an electron coupling to a $W^{-}$ and producing an electron neutrino $e\rightarrow \nu_{e}W^{-}$. Is something like $$\frac{-g_{w}}{2\sqrt{2}}\bar{\nu}_{e}\gamma^{\mu}W^{-}_{\...
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Can Higgs particles move faster than the speed of light in the high energy (temperature) regime? [duplicate]

In the standard model, Higgs particles have negative mass squared term in the SM lagrangian and hence, the Higgs is tachyonic in nature. This isn't a problem since -at low energy (temperature)- the ...
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How does SUSY differ from just having standard model (SM) particles in new Lorentz Group representations?

Under the standard model (SM), it is the irreducible representations of the Lorentz group which allows us to classify particles according to their spin. We can then further label particles using the ...
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Confused about helicity suppression in the decay $\pi^- \rightarrow \mu^- \overline{\nu}_\mu$

I know this question has been asked a few times before here in various ways, but I haven't found answers which helped me a lot. For one, the class I am in is not using any of the underlying math, so ...
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In the unified electroweak theory, do the gauge bosons couple to right handed states?

In the weak interaction the gauge bosons couple to left handed chiral states only. When the two interactions are unified do the bosons couple to both left and right handed chiral states?
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What is the Mathematical description of Weak Interaction at low energies?

Introduction When I started to study gauge theory the mathematical road map seemed to be quite "simple". After all the concepts and notions about principal the differential geometry of fibre ...
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Charged current $e^-e^+$ weak interaction Feynman diagram

I am new to the weak interactions and in particular to the interactions given by charged current interaction lagrangian $$ \mathcal{L}_{int}^{CC} = \frac{g}{2\sqrt{2}}\left[J^{\mu}W^{+}_{\mu}+J^{\mu \...
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What is the value of Heisenberg Uncertainty in position $Δχ$ for a free electron at rest? [duplicate]

Any analytical calculation of this value included in a canonical answer would be nice! We know according to HUP that: $$ \Delta x \Delta p \geq \frac{h}{4 \pi} $$ $\Delta x=$ uncertainty in position $\...
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Standard Model $\rho$ parameter with changing Electroweak gauge symmetry

In Standard Model Electroweak Theory (Governed by $SU(2)_L$ gauge symmetry), $\rho$ parameter is defined as $\frac{M_W^2}{M^2_{Z^0}\cos^2{\theta_w}}=1$. Where $M_W$ and $M_{Z^0}$ are the SM $W$ and $Z^...
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How to evaluate effective Feynman diagrams in the standard model?

I was reading the "Weak Hamiltonian, CP Violation and Rare Decays" by Andrzej J. Buras and, in the page 57 I don't understood how he calculate the effective Feynman diagrams for to get the ...
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How could the neutrino be a Dirac particle

I'm reading up about neutrinos now and I understand the possibility of neutrinos being Majorana particles and further theories can be thought of from that (like the seesaw mechanism). I'm still very ...
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What prevents $K^0$ from decaying into $K^+ e^- \overline{\nu}_e$?

Energetically it is just possible for a neutral kaon to decay into a charged kaon, electron and antineutrino, namely: $$K^0 \rightarrow K^+ e^- \overline{\nu}_e$$ Indeed a mass difference of a few ...
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Why the electron having a relative light mass $511keV$ is so small, upper limit $10^{-18}$m, in the SM? [duplicate]

Usually in particle physics larger mass refers to a smaller cross-section of a particle or atom thus a smaller sized particle. How a so relative light mass particle only $511\,\mathrm{keV}$ can be so ...
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Does the theoretical prediction of the $W$ boson mass rely on the mass of the $Z$ boson?

Regarding the recent problem of discrepancy between theoretical and experimental value of $W$ boson mass: I do remember that standard model gives only a relation between $W$ and $Z$ mass and not a ...
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Any details on deep inelastic scattering? [closed]

The article on Wikipedia is rather scanty and I couldn't find more info in previous questions. I hope you will cot consider this as a multiple question since all queries are details of a single issue. ...
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$W$ boson $0.1$% heavier than predicted by 7$σ$? [closed]

Quite recently more and more refined experimental results pile up that put the SM under stress and tend to disprove more and more its predictive power and potentially are the start-up point of new ...
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What would be the impact of slighty higher mass for the $W$ boson? [closed]

With the recent announcement from CDF https://cerncourier.com/a/cdf-sets-w-mass-against-the-standard-model/ placing it at the mass at $$80,433.5 \pm 6.4\; \text{(stat)} \pm 6.9\; \text{(syst) MeV},$$ ...
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How are Hydrogen Atoms Described in Standard Model? [closed]

Specifically, in order to calculate the quantities like emissivity or the cross section of photon resonant scattering by hydrogen atoms, what logical deduction route should we follow, starting from ...
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How could negative $W$ "eat" the positive Goldstone bosons $\phi_1$ and $\phi_2$?

In the Standard Model, the Higgs field is $\Phi=\left(\begin{array}{c}\phi^+\\\phi^0\\\end{array}\right)=\frac{1}{\sqrt{2}}\left(\begin{array}{c}\phi_1+i\phi_2\\\phi_3+i\phi_4\\\end{array}\right)$. ...
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Do entropic forces inherit de-facto force carriers from confinement?

Do entropic forces inherit force carriers from the forces responsible for the confinement that gives rise to the entropic force? What if you have multiple different fundamental forces combining to ...
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Is the Standard Model, in some sense, special relativity plus everything possible?

I found this intro to QFT on YouTube really helpful (and apparently I'm not the only one). Let my try to summarize it: We start with Minkowski space. We want to add a field to it, but there are only ...
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How to identify which particles can run in the loop for Higgs decays to gluons and photons

I am following the lecture notes given in "Higgs physics within and beyond the Standard Model" by HE. Logan and on pages 21 to 24 she discusses Higgs boson decays to photons and gluons which ...
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A common standard model Lagrangian mistake?

A common standard model lagrangian is written in a cup like this. It appears in many places also on a T shirt. But isnt that there is an obvious mistake? That the Dirac lagrangian is already itself ...
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Do quarks have a non-zero electric dipole moment?

It is written here, in this PSE link that an electron has a measured perfect spherical charge density therefore a zero electric dipole moment (i.e. perfect monopole charge). My question is, are quarks ...
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What would be the implications in the Standard Model if we experimentally verified that the electron charge has an intrinsic electric dipole moment?

It is known also by recent experiments that the electric charge distribution in space of an electron has been measured with great accuracy to be perfect homogeneous thus essentially geometrically a ...
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Excited quark production

I found a Feynman diagram for excited quark production via an up quark and a gluon interacting (https://www.quantumdiaries.org/2015/02/04/lhc-run-ii-excited-quarks/). Is this quark gluon fusion and if ...
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Is sub-atomic particles (quarks) bunch of compressed photons? [closed]

According to theoretical physics,protons,neutrons and electrons are made up of sub particles called quarks which are the building block of matter (baryons). what if the quarks are bunch of compressed ...
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