All Questions
Tagged with particle-physics quantum-chromodynamics
209 questions
1
vote
1
answer
43
views
Confinement energy scale and boosts
Imagine a reference system where a certain proton is standing still in front of us. We measure its energy and we realize it's very low, so that the strong coupling constant $\alpha_s$ is pretty high ...
- 11
0
votes
0
answers
24
views
Hard Process and Parton Shower in QCD
I'm studying QCD for the first time and quite stuck in a few terminologies.
What are the "hard process" and "soft process" in QCD? What are the fundamental differences between ...
0
votes
1
answer
57
views
What is the difference in the interaction between quarks in $\Sigma$ and $\Lambda$ baryons?
$\Sigma^0$ and $\Lambda^0$ consist of $uds$. $\Sigma^+_c$ and $\Lambda^+_c$ consist of $udc$. $\Sigma^0_b$ and $\Lambda^0_b$ consist of $udb$. There is probably something similar for $udt$. They have ...
- 226
0
votes
1
answer
84
views
Reference to applications of QCD
Applications of QED are discussed in many textbooks (computation of various cross sections, Lamb shift).
I am looking for a reference to a discussion of applications of QCD.
0
votes
0
answers
41
views
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
97
views
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 ...
- 4,366
1
vote
0
answers
59
views
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
vote
1
answer
33
views
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
vote
1
answer
146
views
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:
...
- 335
1
vote
2
answers
229
views
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
...
- 405
0
votes
2
answers
104
views
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
3
votes
0
answers
73
views
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
votes
1
answer
76
views
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
2
votes
0
answers
53
views
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 ...
- 8,971
-1
votes
1
answer
183
views
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