All Questions
Tagged with quantum-chromodynamics color-charge
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Is color charge internal symmetry or global symmetry?
I was told the color charge in the standard model could not be observed directly. This sounded like the gauge field $\vec A$ in the electromagnetism. However, it is a discrete charge and does have ...
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$SU(3)$ color charge
Is the color charge the Noether charge due to the "global" $SU(3)$ symmetry of the QCD Lagrangian, or is it due to the "local" symmetry of the QCD Lagrangian?
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Colour Factor in QCD Pair Annihilation
My question occurred when I was reading Introduction to Elementary Particles by David J. Griffiths. In chapter 8, part 8.5, he is calculating the colour factor of quark-antiquark annihilation.
My ...
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When can colour charge indices be equated?
I'm currently studying QFT and QCD for the first time and I have a question about the colour charge indices given below. I was asked the following question:
(a) Derive the Feynman rule for the 3-...
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What does conservation of color charge mean for mixed states in QCD?
In quantum chromodynamics, in an interaction in which a quark and an anti-quark exchange a gluon, the color charge must be conserved. When we are talking about base states like $r\bar{b}$ it seems ...
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Is colour the conserved charge of global $SU(3)$ color symmetry?
Consider the Lagrangian consisting of three Dirac fields
$$ \mathcal{L} = \sum_{a=1}^3 \bar{\psi}_a ( i \gamma^\mu \partial_\mu - m ) \psi_a$$
where $a$ is an internal index labelling the colour ...
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Quantum Chromodynamics and Group Theory
I know nothing of QCD, but I was watching this youtube video and pondered on whether the additive structure described is a group, and if so, which is it?
As of now, I know the group must contain the ...
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Justifying the identification of eight gluons with the ${\bf 8}$ from ${\bf 3}\otimes{\bf 3}^*$
When we combine the fundamental ${\bf 3}$ and antifundamental ${\bf 3}^*$ of color $SU(3)$ of QCD i.e. single quark of three colors and a single antiquark of 3 anticolors, nine states are obtained. ...
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Can black holes have colour charge? [duplicate]
Does the no hair's theorem take into account all the elementary particles and forces, and in particular can a black hole have color charge?
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Why $\pi^+$ meson possible combinations of quarks is only three?
I am a starter at nuclear and particles physics. I am reading particles and nuclei an introduction to the physical concepts. There was a paragraph about Colour-neutral particles and how only ...
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How can I describe, in QFT, Weyl spinors coupled to a strong version of the gluon gauge field?
Let's assume a massless Weyl-spinor field. My aim is to let them interact by a gluon-like gauge-field, which has a bigger much bigger coupling, color charge, than the standard color interaction.
This ...
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Is the concept of bicolored gluons mathematically precise/meaningful? Please explain
Each flavour of quark carries a colour quantum number: red, green or blue. I know what it means mathematically. But elementary textbooks (e.g, particle physics by Griffiths) also say that gluons are ...
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Quantum chromodynamics - why are there no $rrb$ or $ggr$ terms?
$$\Psi_{colour}^{qqq} = \frac{1}{\sqrt{6}}(rgb + gbr + brg -grb - rbg - bgr)$$
My lecturer stated that there cannot be any $rrb$ or $ggr$ terms in the expression above. I would like to understand what ...
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If a spin singlet cannot change, how can it interact with electromagnetism?
Let's say there's a Hydrogen atom in a spin triplet state.
$$ | \downarrow\downarrow \rangle$$
Now let's say a photon with spin 1 came along abs was absorbed by the atom. We don't know if the proton ...
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A gluon can have nine independent, bicolored states. How are some of the additions of these individual states, like $r\bar{r}+g\bar{g}+b\bar{b}$?
This came from the 25th page of the following pdf: http://www.gammaexplorer.com/wp-content/uploads/2014/03/Quarks-and-Leptons-An-Introductory-Course-in-Modern-Particle-Physics.pdf
Sorry if I am asking ...
