Quantum-ChromoDynamics (QCD) is the quantum field theory believed to describe the strong nuclear force.

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How do we know that nuclear physics corresponds to low energy QCD?

One often hears the phrase "most of nuclear physics is in the low energy regime of QCD, where strong coupling constant is large ...", with the following diagram being invoked: How does one know ...
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Reasons for choosing $SU(3)$ as the color group vs. $SO(4)$

What are the reasons that $SU(3)$ is used for QCD? Why wouldn't the simpler & smaller group $SO(4)$ make a better candidate?
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How to compute this loop integral? [closed]

I have a gauge boson that splits into two scalars and the loop is closed by a gauge boson as shown in the picture. The incoming boson has $\mu$ index while the boson that runs in the loop has momentum ...
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The counting of all possible baryons quark combinations

I would like to ask how do you count the number of possible quark combination that could possibly exist in a baryon. I know certain spin symmetry or orbital momentum symmetry have to be conserved. But ...
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174 views

Is There Any Difference Between Strong Quarks Force and Strong Nuclear Force?

the spectrum of quarkonium and the comparison with positronium potential for the strong force is: $V(r) = - \frac{4}{3} \frac{\alpha_s(r) \hbar c}{r} + kr$ (where the constant $k$ determines the ...
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Has the mass of longitudinal and perpendicular spin 1 mesons been measured separately?

This might be a silly question. When the mass of a spin 1 meson is measured, is there a way to check whether it is the same for all polarizations? Is such a meson mass the same for longitudinal and ...
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Axion domain walls and QCD phase transition

Now it is known that QCD phase transition corresponds to crossover. This it seems that no topological defects is produced during phase transition. Do axion domain walls arise during QCD phase ...
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22 views

What tell us know that Parton distributions and Fragmentation function are non-perturbative part of QCD?

I read some document I see Parton distributions and Fragmentation function are non-perturbative part of QCD. Have document tell about that?.
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Why is shown three-gluon diagram a two-loop diagram?

Why is this QCD diagram a two-loop and not a three-loop diagram? Thanks for your help!
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How to count completely symmetric wavefunctions can be made by 6 (u, d, s, $\bar{u},\bar{d},\bar{s}$) quarks to form Baryons (i.e., 3 particle state)?

(Excluding antisymmetric part i.e., colour part) Peskin said 6 (particles + Anti-Particles) "guys" make (6(i.e., total "guys") x7x8)/(3x2)= 56 total symmetric state. How? There are 10 (decuplate) ...
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Hadron Annihilation - what happens with the constituents

When a Hadron and its antimatter equivalent annihilate, what happens to the QCD "soup" (for lack of an appropriate term) from each? Eg, the valence quarks in a proton - antiproton event, to they pair ...
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Can we just replace the finite part of $Z_m$ in a renormalization scheme at leading order

Suppose that we have to determine the finite part of $Z_m$ how it differs from common schemes, but we are free to choose the other renormalization constants in QCD (at Leading order). Could we make ...
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Problem in the derivation of the Ward identities

This is a follow up to my previous Phys.SE question. The last equation in that question is $$-a\frac{1}{k^2+i\eta}k^{\lambda}i\Pi_{\lambda\rho}(k)iD^{\rho\nu}(k)=0$$ which we can further simplify as ...
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Computing the ratio of unpolarized QED and QCD cross section

How is the last equality of the equation $$ \frac{\sigma_{QCD}}{\sigma_{QED}}=\frac{1}{3*3}(tr T^a T^b)^2=\frac{2}{9} $$ derived, where $T^{a,b}$ are the basis matrices of SU(3)?
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33 views

Reference for the non-perturbative origin of the baryon masses

I'm looking for nice introductions to the non-perturbative generation of the baryon masses.
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Isospin and Energy

I would to know if there is a correlation between isospin and energy. Consider for example the $\eta$ meson ($I =0$) and the pions($I=1$). The $\eta$ turns out to be much heavier then the pions ...
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Yan - Drell process

I'm looking for more information about Yan - Drell process but didn't manage to find a good place to learn from (still looking for one). I understood that this process can help us to understand the ...
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Reduced graphs and pinch-singular surfaces

I am reading a book on perturbative QCD by John Collins. In Chapter 5, the terms reduced graph and pinch-singular surface are used for the analysis of mass singularities. However, their meanings are ...
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The ridge at LHC

One of the results obtained by LHC is the following diagram for p-Pb collisions: I would like to understand what is actually depicted in the figure, what should we expect based on theoretical ...
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480 views

Pion Decay and Fractional electric Charge disappeared, why?

Since the charged pions decay into two particles, a muon and a muon neutrino Fractional electric Charge disappeared, why? The decay proceeds by the weak interaction $W^{+}$ and can be visualized in ...
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Cramer's rule, Origin of Quarks Fractional electric charge? [closed]

In linear algebra, Cramer's rule is an explicit formula for the solution of a system of linear equations with as many equations as unknowns. 2u+1d=1 1u+2d=0 $$a_1d+b_1u=c_1$$ $$a_2d+b_2u=c_2$$ ...
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Could the fractional model of Quarks electric charge turn out to be false? [closed]

The delta baryons (also called delta resonances) are a family of subatomic hadron particles which have the symbols $\Delta^{++}$, $\Delta^{+}$, $\Delta^{0}$, and $\Delta^{−}$ and electric charges +2, ...