All Questions
Tagged with standard-model quarks
324
questions
-1
votes
0
answers
13
views
Jet events and Deeep Inelastic Scattering (Scaling Behavior) at the same time?
I am a philosopher of physics, so I already apologize for potential ignorance. I have also graduated in physics, but I now analyze problems on another level and also forgot some of the mathematical ...
0
votes
2
answers
116
views
Why does the up and anti-up quark combine into a pion and not a photon?
im currently studying a level particle physics and im confused about this. Particle annihilation occours when a particle meets its corresponding particle, converting their mass energy into two photons,...
- 3
0
votes
1
answer
60
views
Why is isospin utilized in determining the branching fraction of $K_1(1270)\to K\pi\pi$ final states?
The branching fraction of $\mathcal{B}_{K_1 \rightarrow K^{+} \pi^{+}\pi^{-}}$ is determined by $$\mathcal{B}_{K_1 \rightarrow K^{+} \pi^{+}\pi^{-}}=\frac{1}{3} \times \mathcal{B}_{K_1 \rightarrow K \...
- 17
0
votes
0
answers
31
views
Understading dimensions in quark bilinears
I have encountered myself with the following definition for $\pi$-fields as quark bilinears:
$$
\pi^a = i\bar{q}\tau^a \gamma_5 q \ ,\quad\text{with }\ q = \left(\begin{array}{c}u\\d\end{array}\right) ...
- 601
3
votes
1
answer
104
views
Why can't we insist that the strong interactions must preserve $CP$?
I'm having some trouble wrapping my head around the strong $CP$ problem. I know that the non-trivial vacuum structure of QCD induces the topological theta term in the strong sector of the SM, which is ...
1
vote
1
answer
98
views
Quark condensate and VEV of $\pi^0$
In David Tong's lectures on the Standard Model I saw that there is a quark condensate, which is just a Vacuum Expectation Value (VEV) of the $\bar{q}_{Li}\, q_{Ri}$ operator,
$$
\left< \bar{q}_{Li}...
- 1,611
1
vote
1
answer
81
views
Quark Combination of Hadrons
I am trying to understand the different combinations of quarks in a hadron. I have seen that the positive pion is written as $\pi^{+}=u\bar{d}$, but I have not seen it written in the opposite order. ...
- 35
3
votes
1
answer
70
views
Isospin doublet and quark content from contraction of quarks
Let's introduce a quark $SU(2)$ doublet. We are in the $m_u \approx m_d$ limit. So we have
$$
q = \begin{pmatrix}
u\\
d
\end{pmatrix}.
$$
Then we can construct the Nucleonic field
$$
N := q q q = \...
- 1,611
1
vote
1
answer
118
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:
...
- 325
1
vote
0
answers
49
views
How are $\pi$ Mesons Created in the Residual Strong Interaction?
Watching this episode of PBS Space Time, they run an animation of how pi mesons are exchanged by nucleons as the residual strong interaction to overcome proton electromagnetic repulsion.
https://youtu....
- 23
4
votes
0
answers
64
views
How can a proton be stable if binding energy *increases* it's mass? [duplicate]
A hydrogen atom weighs 13.6eV less than a proton + electron. This missing energy, which is tiny compared to the rest mass of almost a GeV, was carried off by a photon when the atom formed.
Nuclei show ...
- 6,531
18
votes
3
answers
2k
views
Charge distribution of a proton
I've been studying high-school level physics and I noticed that protons are composed of up-up-down quarks. It is known that fields can be non-uniform due to geometries: Earth's gravity field is not ...
- 183
1
vote
1
answer
71
views
Quark charges - parton-distribution function - factor 5/18
I got the following from Thomson’s Modern Particle Physics and some other sources.
The factor 5/18 distinguishing electron-DIS and neutrino scattering experiments is a basic proof for quarks and their ...
- 95
3
votes
0
answers
67
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 ...
0
votes
1
answer
116
views
Lagrangian for quarks and pions
I need to understand how starting from the free Lagrangian
$$
\mathscr{L} = \bar{q}(i \not\partial - \hat{m})q
$$
and based on the chiral angle associated with the pion field and the quark field ...
- 21