# Tag Info

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In QM most stuff boils down to particles. For example, electromagnetism is mediated by photons and EM radiation is literally just beams of photons. We should then have a couple of obvious candidates for strange and new kinds of radiation. The strong force is mediated by gluons and there are 8 types of gluons. At a larger scale (like with atomic nuclei) ...

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To add to the other answer: Your intuition is right in a way. The fact that the $W$ and $Z$ bosons are so heavy is the reason for the weakness of the interaction. For example, $\pi^+$ mesons can decay over the weak interaction, the process is described by the following Feynman diagram: According to the Feynman rules, the probability amplitude of such a ...

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When e.g. a neutron decays, there is no "real" W-boson inside, in the sense that it could be detected at every point. Instead, the decay of the neutron involves a "virtual" W-boson, a W-boson that only exists for a very short time. Quantum mechanics allows the energy conservation law to be violated by $\Delta E$ for a very short time $\Delta t$ as long as $\... 2 There is the statement in the video, "particles vibrate", and vibrations lead to the concept of frequency. The confusion comes because in fist quantization, the solutions of the Schroedinger and Dirac equations, the wavefunctions have a sinusoidal dependence, which lead to a probability density distribution for the particles, and the de Broglie wavelength ... 3 If a particle changes flavor, it's a charged-current weak decay. Example:$n\to pe\bar\nu$. If there's a neutrino in the final state, it's a weak interaction. Decay example:$\pi^+\to\mu^+\nu$. See also neutrino scattering. If parity isn't conserved, it's a weak interaction. Examples:$K^0 \to 2\pi$and$K^0 \to 3\pi$. Note that kaon decays and$K\...

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The gauge symmetry group associated to the SM is $SU\left(3\right)_{c}\times SU\left(2\right)_{L}\times U_{Y}\left(1\right)$. Then we can not build the lagrangian of the SM with terms of the form $m\bar{\psi}\psi$ because they are not gauge invariant. A term of this kind mix the right and left handed parts, which transforms differently. In order to give mass ...

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Some care is needed when talking about quantum fields because they are a mathematical formalism for describing the properties of particles, and it is unclear to what extent a quantum field can be regarded as a physical object. Many of us are guilty of sloppy terminology such as the energy of a quantum field or transfer of energy betweebn quantum fields. ...

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There are flavor changing weak interactions mediated by the charged $W^\pm$. In the cases you cite I would agree that flavor symmetry would not permit these interactions $uu\rightarrow cc$ etc.

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The forces entering the standard model all are symmetric, with zero mass exchange particles at high energies before symmetry breaking. It is one of the beauties of the standard model. Any proposed model for further complexity , preons etc has to predict phenomena which are outside the standard model and at the same time, incorporate the phenomena which ...

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The problem with "weak charges" is that electroweak symmetry is spontaneously broken. Before the symmetry breaking, electroweak symmetry is described by an $SU(2)_L \times U(1)_Y$ gauge group.This amounts to three charges: weak hypercharge $Y$ for $U(1)_Y$ and weak isospin (total isospin $T$ and third component $T_3$) for the $SU(2)_L$. Some examples of ...

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You're mixing a few things up here. When you say "three" for the strong force, you're counting the number of colors of quarks, but when you guess "three" for the weak force, you're counting the number of force carriers. These are two different things. For example, if you counted the number of gluons (the force carriers for the strong force), you'd get ...

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I would say two, which is pleasantly consistent with the $SU(2)$ structure of the weak force. One is the coupling strength with the $Z$ boson, and one is the weak isospin which is raised and lowered by the $W^\pm$.

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According to the CPT thoerem, the choice of positive parity for particles and negative parity for antiparticles is just as arbitrary as the choice of positive charge for protons and negative charge for electrons.

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I think the above picture with captioning below answers the question best, at least for me. Basically the green quark emits a green-antiblue gluon, turning it blue. This gluon is absorbed by the blue gluon, and it changes from blue to green, restoring the color symmetry and keeping the Baryon overall colorless. And it happens so fast that no overall Baryon ...

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No, not at all! The color of the quarks has no effect whatsoever. If you're studied intro physics, you know that a potential $V(x)$ is identical in every way to a potential $V(x) + V_0$ for some constant $V_0$. Now consider two hydrogen atoms, where I've set the potential at infinity to be $3 \text{ V}$ for one of them and $4 \text{ V}$ for the other. ...

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Hadrons come in 2 families: baryons and mesons. Both of them consist from colourless combinations of quarks. Mesons contain pairs of quarks of colour-anticolour and hadrons contain 3 quarks of different colours making them white in analogy with regular colour perception. You are right that quark can change its colour by interaction with gluons, but the ...

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OK, since my name was taken in vain I suppose I am obliged to clarify my comment further. My invitation was to contrast charge oscillations to strangeness oscillations in the $K^0-\bar{K}^0$ system, not to use the latter to argue for the former. The finally mutated question I am addressing is “Why are there no charge oscillations and superpositions of ...

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If you take an electron and a proton there is a strong electromagnetic force between them because the electron has a charge of $-e$ and the proton has a charge of $+e$. However suppose you combine the electron and proton into a hydrogen atom. The hydrogen atom has a net charge of zero so there is no strong electromagnetic force between two hydrogen atoms. ...

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This is related to the so-called "colour charge" carried by particles involved in strong interaction. Although at first it was proposed to allow same quarks exist inside the baryons (despite Pauli exclusion principle), it is also used to describe the ability of hadrons to be free of confinement — only colourless particles (or white) can be free. This is not ...

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It is not true that scale invariance requires strong interactions. After all, free scalar field theory is scale invariant (and so is classical electromagnetism). In high energy interactions approximate scale invariance emerges because asymptotic freedom implies that free field theory is indeed a useful starting point. QCD is subtle because we cannot study ...

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Typically, we solve a partial differential equation (analytically if we can, but often we can only do numerical calculations), where in the input of the problem we put the known quantities Physics started with observations of nature, and mathematics developed which could model the observations and measurements and predict future set ups. Beginning with ...

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There is a clear mistake in what he says : the mass does not come from the interaction with the higgs particles in it self. In essence, for the mass due to the Higgs mechanism, the Lagrangian contains originally massless particles. This is due to the requirement of gauge symmetry. Mass terms are not gauge invariant. The higgs mechanism is a dynamical ...

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In a few words, as Luke Pritchett writes, the Higgs mechanism provides us description of particles mass without breaking of the unitarity, i.e., breaking gauge symmetry explicitly. It is interesting fact that even if You start from electroweak theory in the broken phase and don't know about Higgs boson, $W/Z$-boson and existense of hidden gauge invariance (i....

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Because "spontaneous symmetry breaking" does not actually break any symmetries. This is a pretty important principle that is not always adequately taught. In spontaneous symmetry breaking the symmetry in question is always a full symmetry of the theory. The difference between a spontaneously broken symmetry and an unbroken symmetry is just in how the ...

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Who forbids me to think that the particles are not equipped with a primitive form of identity that arises intelligently to your measurements and you can not behave as a quality? "arises intelligently" is not in the physics domain. It is metaphysics, this assigning intelligence to particles, and there exist such metaphysical "theories" but their ...

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The use of the term mediator in this question appears to refer to gauge bosons. These couple to fermions or other particles that have their coupling charge. In the case of QCD gluons, the gauge particle of force, has color charge and couples to itself. This Higgs boson or field is not of this nature. The elementary idea is that the Higgs field consists of ...

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Yes but with lots of subtleties to be described in (2). The main questions to be settled are: whether we count just the fields (configuration space) or fields and their derivatives (phase space) whether we count the fermions along with bosons, or separately (I will count them separately), and whether we double the number for them because the Standard Model ...

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@Michael Brown is right. The SM has 12 exactly conserved charges. All local invariances, a fortiori also imply global invariances, if you ignore (for the sake of argument) the spacetime variability of transformation parameters/angles. So SU(3) has 8, not 3 conserved charges, RG, BG, .... The group has 8 generators. Likewise, SU(2) has 3, not 2 conserved ...

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Of the Higgs for Waldegrave analogies, Tom Kibble's is by far the best (celebrity or a rumor of a celebrity crossing a crowded room of media people), but there are several inconsistencies in this analogy. For one thing, these are bosons, and that means, among other things, that it is possible for the bosons themselves to occupy the same space at the same ...

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Representation of $SU(2)$ is pseudo-real. Which means, if $\mathbf{[2]}$ and $\mathbf{[\bar{2}]}$ are the fundamental and anti-fundamental representation of $SU(2)$, then there exists an anti-symmetric matrix $\cal{C}$, which connect both of them, as $\cal{C}\mathbf{[2]}\cal{C}^{-1}=\mathbf{[\bar{2}]}$. Another way of saying this, both $\mathbf{[2]}$ and \$\...

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The CKM, PMNS matrices are mathematically absolutely analogous, except that the values and even hierarchies of all the parameters are entirely different in the two cases. (Also, we don't know whether right-handed neutrinos exist and whether the effective Majorana masses may be derived from Dirac masses or something else.) But both matrices may be reduced to ...

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