All Questions
Tagged with quantum-chromodynamics particle-physics
208
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QCD parton shower hard scale
Currently I'm studying parton showers from QCD and I'm having trouble with understanding how the hard scale $Q$ is related to the virtuality and energy of the parent parton. The Sudakov factor $\Delta(...
- 291
-4
votes
1
answer
81
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Yang-Mills mass gap caused by gluonballs or because dark matter WIMPs?
Yang-Mills quantum field theory predicts the existence of the lightest massive Bosonic (i.e. integer spin) particle.
This massive Boson will be much lighter than the $W$ and $Z$ Boson and therefore ...
- 4,170
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0
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52
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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 ...
- 81
1
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1
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What is the meaning of dynamically generated states in particle physics?
In hadron spectroscopy, a structure may be interpreted as various "configurations", such as conventional quark-antiquark states, tetraquarks, hybrid states, dynamically generated states or ...
1
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1
answer
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Do all antiquarks carry and anti-color charge, or can they carry RGB color charges as well?
I know there are antiquarks with anticolor charges. Are there also antiquarks that instead carry color charges?
Basically, which of these lists describes the types of quarks that there are:
List one:
...
- 325
1
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2
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172
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Why are two gluons needed for Feynman diagram?
Why do we need two gluons for the decay $$\pi^-+ p\rightarrow\pi^-+n+\pi^+\:\:?$$
If we have always the gluon $$\frac{1}{\sqrt{2}}(r\bar{r}-g\bar{g})$$ it should be possible with only one gluon
...
- 494
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2
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74
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Difference between $ SU(3)$ and $ SU(3)_c $ group
I am reading quark model. I don't understand what's the meaning of a color $SU(3)$ or $SU(3)_c$ group and how it differs from a general $SU(3)$ group. Please elaborate.
- 377
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When do pairs of quarks form jets vs mesons?
For certain processes with low momentum transfer, such as the Kaon decay shown below, quarks will form bound states of mesons.
Whereas for higher momentum-transfer processes, such as the decay of an ...
2
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1
answer
71
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How relevant is the electric charge of quarks within hadrons?
Given that each quark flavor has a particular electric charge (i.e., either +2/3 or -1/3): how do these charges effect the internal dynamics of hadrons? Do the attractive and repulsive effects of ...
- 307
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47
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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 ...
- 1
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When to consider and when not to consider the loop contributions from light quarks?
Consider the following Lagrangian:
$$
\tag 1 \mathcal{L} = \frac{\partial_{\mu}a(x)}{f}\sum_{q}\bar{q}\gamma^{\mu}\gamma_{5}q
$$
This is a Lagrangian of the axion-like particles (ALPs) $a$ interacting ...
- 8,891
-1
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1
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153
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Why is the electromagnetic force not an emergent property of the strong force? [closed]
Two up quarks in a proton lead to an imbalance, which results in the proton having the ability to attract electrons. Two down quarks in a neutron lead to balance in the electromagnetic force, leading ...
- 29
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139
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Integral of the square of the spectral density in a quantum field theory
The quantity of interest is
$$
\int_0^\infty dE \, \rho(E)^2
$$
where $\rho(E)$ is the spectral density in a Quantum Field Theory. I am wondering whether
it has any physical meaning, and
it can be ...
- 1
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76
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Spin and rotation of gluon field components
The gluon field has 4 spacetime components: $A_\mu = (A_0, A_1, A_2, A_3)$, like the electromagnetic field.
Firstly, how to find each component of the gluon field?
And how to perform a rotation on ...
- 67
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31
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Comprehensive references to learn about the flavor $SU(3)$ model of hadron classification
What are some comprehensive references to learn about the flavor $SU(3)$ model of hadron classification based on group theory? Textbooks, Lecture notes, videos anything will do. I need to learn this. ...