# Tag Info

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Typically, when you read about the Standard Model, you are reading about the model of the fundamental particles and their interactions, including: 6 quarks Up Down Charm Strange Top Bottom 6 leptons Electron neutrino Electron Muon neutrino Muon Tau neutrino Tau particle The force carrier particles (gauge bosons): The photon, which mediates ...

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As anna mentioned, there are non quark models which clarify exotic hadrons. In principle, they are allowed in Quantum Chromodynamics (QCD). Non-quark models predict 1.hybrid mesons: Include quark anti-quark pair and gluon. 2.Glueballs: Gluons are their own bound states. 3.Exotic hadrons as in figure below which exchange pion at low energies (couple ...

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The fact of the matter is that there are no stable mesons, that might conceivably form states bound by the strong force, as the nucleus is bound. Within the nucleus there exist virtual mesons, i.e. described as pions etc but not on mass shell To a large extent, the nuclear force can be understood in terms of the exchange of virtual light mesons, such as ...

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The string-net condensation is a general construction to obtain gauge fields and fermions. The chiral fermion problem refers to the fact that in the Standard Model (SM), the SU(2) gauge field only couples to the left-handed fermions but not the right-handed fermions. However in the (early version of) string-net condensation, the emergent gauge field will ...

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While electrons are point particles in the sense that their position eigenstates are (as far as we know) $\delta$-like. Photons can't be said to be point particles in this sense, as you cannot transform to their rest-frame (although they are featureless with respect to small scales as far as we know). The correct way to thing about electrons and photons is ...

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All these links are accessible at a non-mathematical level, and they are by recognized scientists (with the exception of the first link). (1) To start, see the "Simple English Wikipedia", which explains what the Higgs effect is, and the reason for the Higgs effect: http://simple.wikipedia.org/wiki/Higgs_field. (2) The difference between the Higgs boson and ...

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In the standard model, there is no elementary spin 0 boson being electrically charged (but there are many charged spin 0 composite particles). However, in many extensions such as supersymmetry, there are such particles: the scalar partner of the electron, the selectron carries the same charge as the electron. The anti-selectron is the spin 0 partner of the ...

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Answer to the main question: It is a well regarded fact that the terminology unified electroweak interaction is a bit of an abuse of terminology. What the term means is that both Quantum Field Theories, the Hypercharge ($U(1)_Y$) and Weak ($SU(2)_L$), are unified in a common framework, which predicts the low energy electromagnetism ($U(1)_{em}$) through the ...

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$Λ_{QCD}$ is measured in processes where the strong coupling constant and other measurables vary with momentum scale $Q$. For instance, evolution of nucleon structure functions measured in lepton-nucleon deep-inelastic scattering, heavy quarkonia decays, collider jet physics, electroweak physics at the Z, ... Most results are in the 200 to 300 MeV range. ...

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A spin-spin interaction is really a magnetic moment - magnetic moment interaction, where the magnetic moment of each particle is proportional to spin. [Of course, it might be a chromomagnetic moment - chromomagnetic moment interaction if two quarks are interacting, as they are here.] In any case, the interaction term goes like $\vec S_1 \cdot \vec S_2$. ...

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You're right that the reaction fails to conserve baryon number. The change in strangeness is a strike against the reaction, but not a fatal one; after all, the strange $K$ mesons decay into various mixtures of zero-strangeness mesons, charged leptons, and neutrinos. The thing to notice is that only the charged weak current, mediated by the $W$ boson, ...

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First of all, the oblique parameters S,T and U are defined to be zero within the Standard Model (SM). This means, that the SM is a reference and therefore, these parameters are indications for physics beyond the Standard Model (BSM). They account for corrections in the vacuum polarizations of the EW gauge bosons and are chosen in a way, that different BSM ...

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Yes, that is the Higgs potential of the Standard Model. Note that a $\phi^3$ term is forbidden by symmetry (it would not be an $\mathrm{SU}(2)$ scalar), and $\mathcal{O}(\phi^5)$ terms would be non-renormalizable, so this is really the only potential we can write down that does not need other new physics.

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It's a whole lot of questions wrapped up in two sentences. I suggest you look at the standard model. (see below) - and this one doesn't have the higgs, but it was hard to find one the right size to post. All mass is a result of an interaction between particles with rest mass and the Higgs field or Higgs Boson if you like, but I think Higgs field is ...

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They have weak hyperchage, flavor, mass and spin (though the mass states are not flavor states with various consequences). How many more "innate properties" do you want?

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Actually, you can do without complex fields, at least in some general and important cases, and I don't mean replacing a complex field with two real fields. Schroedinger noted that, in the case of a scalar field interacting with electromagnetic field (the klein-Gordon-Maxwell electrodynamics, or scalar electrodynamics), you can use the so-called unitary ...

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What type of fields are you using? If you are working with spinor fields, the representation of Lorentz transformations is complex. So even if the field is real in some reference frame, if you switch to another reference frame it will become complex. There's no way to avoid complex spinor fields.

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There is no non-trivial one-dimensional representation of $\mathrm{U}(1)$ on a scalar field $\mathbb{R}^4\to\mathbb{R}$, but on complex fields $\mathbb{R}^4\to\mathbb{C}$, we have the one-dimensional "phase" representations by $$\phi\mapsto\mathrm{e}^{e\mathrm{i}\chi}\phi$$ for $e\in\mathbb{Z},\chi\in\mathfrak{u}(1)\cong\mathbb{R}$ for $\mathrm{U}(1)$ ...

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What is meant by fractional scaling dimension is exactly what is says: Given a dilatation $x\mapsto\lambda x$, the field/operator $\mathcal{O}(x)$ behaves as $$\mathcal{O}(\lambda x) = \lambda^h\mathcal{O}(x)$$ with $h\in\mathbb{R}$ a possibly fractional or even irrational number. The prime example of quantum field theories in which a fractional scaling ...

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First of all some clarifications to make sure we are on the same page. The phrase "$A_\nu$ is local" is slightly misleading as it implies that A is only defined in some (small) neighborhood of the total manifold/space. This is not true. A is defined everywhere on the manifold. The correct expression is that "the theory is invariant under a local symmetry" ie ...

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HyperLuminal asked: "Does that mean that electrons are infinitely stable?" Think about Dirac's model of an electron, which includes left and right handed contributions. Now add the (Nobel-worthy) Brout-Englert-Higgs idea, that the left-handed bit interacts with a condensate of weak hypercharge, while the right-handed bit does not. This suggests a ...

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This can be explained by thinking about the coupling of fermions to the $SU(2)$ weak gauge field. Let's recap what we know Weyl fermions necessarily appear in two complex representations of the Lorentz group $L$ and $R$. Only fermions in the $L$ representation of the Lorentz group couple to the $SU(2)$ gauge field. CPT is a symmetry of the theory. Now ...

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An experimentalist's answer to: What is the difference between the Higgs Boson particle and an electron moving through the Higgs field? Our experiments found a large number of resonances and particles which fitted beautifully into SU(3) representations, separated by their quantum numbers and occupying unique niches in the representations. The ...

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The statement is true for decays, where lifetimes can be measured. It is not true for interactions though. A suicidal electron meeting a positron has a good probability to disappear, together with the positron, into two gamma rays, at low energies. Electron-positron annihilation It is intriguing that this is not true for neutrinos. If an electron ...

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This is not exactly true. It is believed that net charge is conserved, but there is a weak process called electron capture, where an electron is captured by a nucleus, (usually from an inner "orbital" so there is a spectroscopic signature), a neutrino is emitted and a proton changes to a neutron. So therefore your textbook is wrong!

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Imagine you are an electron. You have decided you have lived long enough, and wish to decay. What are your options, here? Gell-Mann said that in particle physics, "whatever is not forbidden is mandatory," so if we can identify something you can decay to, you should do that. We'll go to your own rest frame--any decay you can do has to occur in all reference ...

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