The quark model postulates that the hadrons such as protons and neutrons have an inner structure; quarks.

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How and why the phrase “quark force increases with distance”?

I have seen that phrase "force between quarks increases with distance" at many resources, some even relatively credible (albeit written for general audience). What is the reason behind that, when ...
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164 views

The Makeup of the Pentaquark

Why is it that when they have the artist's rendition of the Pentaquark it shows two downs, two ups, and one anti-strange quark? Is this or is this just for show? Follow up to this question: if this ...
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52 views

How do quarks have no spatial extent?

I found an answer to a question I had and that is that quarks have no spatial extent. But how is that possible? Everything has to have some spatial extent; to keep continuing on and on, right?
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144 views

Pentaquark spin prediction

Is there a straightforward way to see what the spin of the recently-discovered pentaquark states should be, from the representation theory of $SU(3)\times SU(2)\subset SU(6)$? I can see that from the ...
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33 views

How many combination can quarks form?

How many different combinations can quarks produce? E.g. 2 up quarks + 1 down quark = proton. Is this value going to be infinite?
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heavy quark pair spin states

Apparently, heavy quark pair can have "axial-vector" spin state, "vector" spin state, and two different "tensor" spin states. Can anyone explain to me what they are and why this is the case? Thank ...
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55 views

Is there a theoretic temperature where single quarks might become individually stable?

This question is what lead me to ask this. Strong force between quarks that are out of causal contact and my understanding of the standard model is that the answer is no - but the standard model ...
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58 views

Strong force between quarks that are out of causal contact

This is a rather artificial scenario, but it has been bugging me lately. Background Due to the confinement in QCD, quarks are bound in color-neutral configurations. Any attempt to separate a quark ...
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60 views

Particle Physics Decay Question - Eta Prime Decay Parity/Angular Momentum Conservation

I was hoping someone could clarify why the following decay does not occur: $ \eta ^{'0} \rightarrow \pi ^{0} + \rho ^{0}$ The quark compositions and spin parity are as followed: $ \eta ^{'0} : ...
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1answer
70 views

What is the motion of quarks inside nucleons? [duplicate]

Nucleons consist of quarks which are charged particles. Proton has the quark content of uud and neutron of udd. So, it may be visualized that the down quark always remain between the up quarks inside ...
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9 views

Averaged energy of quark in proton

I need to evaluate scattering cross section $pp \to ...$, where $p$ corresponds to proton and dots denote any final state; more precisely (for a given question), I need to know cross section of $qq ...
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22 views

Quark decay implies particle decay?

For example, since $$s\rightarrow u+\overline{v_e}+e^{-}$$, then sticking a $\overline{u}$ next to the quarks ($s$ and $u$) we get $$s\overline{u}\rightarrow u\overline{u}+\overline{v_e}+e^{-}$$, ...
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Is there a quark conservation law?

The section on particle interactions in my revision guide says that only the weak interaction can change quark types, e.g. when a neutron changes to a proton the down quarks in the neutron are changed ...
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54 views

How to tell if a particle interaction is strong/weak?

Problem: Prove that the reaction $p+p\rightarrow p+K^+$ is impossible, where $p=\text{proton}$, $K^+=\text{kaon}$. (Side question: Is there a specific name for a positive Kaon, just like a "positive ...
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Do quarks violate quantization of charge?

Does existence of various kinds of quarks like up, down, strange, charm, top, bottom violate the quantisation of charge or just redefine it as up quark have charge +2/3 and have -1/3. Or do things get ...
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1answer
41 views

Are all ground state protons the exact same mass and have the same number of elementary particles?

I have read that it is a misconception that a proton only has 3 quarks (2 up and one down). In reality, it seems there are many, many ("zillions" is the number I saw quoted) quarks in a proton. Do ...
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34 views

Is it possible to make use of the gluon field's energy to use is applications?

As we know most of the mass of the proton comes from the energy caused due to the interactions of the quarks with the gluon fields (reference link of this statement ...
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50 views

Where does the mass of particle that is decaying go?

The particle of a heavy quark (such a s a bottom quark) into either an up or down is an actually change I'm mass (if I know what I'm talking about, which I don't think I do, but that's what this is ...
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348 views

Is color charge a quantum mechanical observable?

If I had 2 pions that were identical, except one was comprised of a red and anti-red, and the other was comprised of a green and anti-green, would I be able to perform an experiment that distinguishes ...
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106 views

Ratio of electrons and protons in Universe

What is the relation between amount of electrons and protons in Universe? I expect that the Universe should not be charged, so the estimation is 1:1. But then, why there should be the same amount of ...
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1answer
80 views

Why does gg fusion dominate over q qbar annihilation at the LHC?

The cross section of top quark pair production is dominated at the LHC by gluon-gluon fusion, whereas at Tevatron, quark-antiquark annihilation is more prevalent. Why is this? I know the fundamental ...
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49 views

The Internal Structure of A Nucleon [duplicate]

Just like, in a Bohr model, the atom has a particular structure, what is it like inside of a nucleon? Like, are there particular ways the quarks are arranged, and what about the binding energy that ...
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1answer
40 views

Parameterization of an arbitrary element of $U(2)_L \times U(2)_R$ (Chiral symmetry with two quarks)

When you write down the Lagrangian for two quarks : \begin{equation} \mathcal{L}_\text{QCD}^0 = -\frac{1}{4} G_{\mu\nu}^a G^{a\mu\nu}+ \bar\Psi i \gamma^\mu D_\mu \Psi \end{equation} you find an ...
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116 views

Why do the quarks constantly change colors?

In a hadron the quarks constantly change colors.They,then exchange gluons to remain color neutral.For example a red quark becomes blue by emitting a red and anti blue gluon and then the blue quark ...
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138 views

Quark anti-quark pair creation. Do we need a gluon?

What is the difference between these diagrams? Is the presence of the gluon taken for granted in the second one? and EDIT: I just zoomed into the picture, it is not a single quark state. ...
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189 views

What do quarks look like?

I've heard everything from zero-dimensional points, to squares, and I would love to know what they really look like, or if they have any physical shape.
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70 views

Where does the mass of a nucleon originate in an atom?

The mass of the three quarks in the nucleons make up only about one to two percent of the mass of the nucleons. What makes up the other 98 percent?
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57 views

Can the density of quarks be more than density of black hole? [duplicate]

I have found this list of densities here: http://wiki.chemprime.chemeddl.org/index.php/Density_of_Black_Holes and I am looking for the density of quarks but I have not found it. I was wondering if ...
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130 views

SU(3) antiquark triplet transformation

I'm reading a rather elementary particle physics text, Modern Particle Physics by Thomson. He is staying away from the heavy group theoretic stuff. He derives the transformation law for an SU(2) ...
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27 views

How to calculate U-spin for baryons

I am trying to calculate U-spin for sigma baryons. I don't know why U-spin for (sigma+) and (sigma-) and (sigma*+) is 1/2 but for (sigma*-) is 3/2? I know that (sigma+) and (sigma-) are octet and ...
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24 views

How to calculate D0->K+K- decay with QCD factorization?

I am studying the decay of D0->K+K- and I calculated the result of Branching Ratio by Naive QCD and I wrote all the equations for amplitude and branching Ration and Hamiltonian and... for this decay ...
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5answers
609 views

On the foundations of quantum physics

Quantum physics has to be validated by experiments. But experiments are to be interpreted in the context of quantum physics. Isn'it like a snake biting its own tail? For example, using a scanning ...
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What is the physical meaning of U- and V-spin?

$SU(3)$ group has three $SU(2)$ subgroups. The first one (with generators $\lambda_{1}, \lambda_{2}, \lambda_{3}$ of corresponding algebra) is called I-spin, the second one (with generators ...
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Has the formation of a new quark pair as we separate two quarks been observed or is it only a prediction? [duplicate]

Because of quark confinement we know that as we try to separate quarks appart the energy required will increase, but if the force is strong enough (I do not know if possible in the lab, but at least ...
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126 views

Simplify QCD Lagrangian

How we can derive the electric charge of the field theory for each field? For example lets say that we have the u-quarks (3-colors) and electron that we know that has charge -e) free Lagrangian ...
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4answers
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What are Quarks made of and will they ever decay to this? [duplicate]

What is it that quarks are actually made of? Will they decay into this substance? As the up and down quarks are the lightest type of quark do they not decay? I was thinking that if this could happen, ...
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2answers
448 views

Is a quark bomb possible?

I am wondering about the possibility of making a bomb out of the binding energy of quarks inside hadrons. I know that about confinement and all that, but I wonder if there is a way to harness this ...
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1answer
74 views

What does the mass of a quark mean?

The mass of an electron includes the mass of the electric field it creates. If electrons have a radius, it's known to be small enough that the mass of the electric field would be more than the total ...
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1answer
177 views

What's inside a quark? [duplicate]

What particles make up a quark? We all know quarks (3, uud) make up a proton. I read on Wikipedia they are called "hadrons" ,but how do they work? Is the collection wave functions of the components ...
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Quarks falling in a black hole?

All I know about quarks is that they make up protons and neutrons and you can't really pull a quark pair apart, you just end up with 2 quark pairs because of all the energy you added becomes 2 new ...
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55 views

At what energy do up and down quarks unbind?

At what energy do up and down quarks unbind? Google does not seem to have a clear answer. Could someone please represent this mathematically?
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1answer
155 views

What would be the best way to explain color confinement in quarks? [duplicate]

To someone who is not so experienced in advanced physics, how do you explain or teach them why something as complex as color confinement prevents us from being able to see or prove that there are any ...
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51 views

How could we find preons?

If I understand correctly, scientists were able to find strong evidence for the existence of quarks by using deep inelastic scattering. If quarks (hypothetically) are composed of preons, could we use ...
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1answer
48 views

What underlying structure/framework defines the charge of an antiparticle or regular particle (specifically a proton)? [duplicate]

I can't seem to find an answer to this. For a given configuration, say for a Hydrogen atom: the proton has properties which give it a positive charge. This is a known truth. Now lets take Hydrogen's ...
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1answer
46 views

Unitarity of CKM matrix?

The CKM matrix is known to be unitary. Now, is it just found experimentally? Is the following idea correct? We know that the weak force eigenstate $ \left( \begin{array}{c} d' \\ s' \\ b' ...
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68 views

Origin of CP violation in CKM matrix?

I have already seen this question but I am not very familiar with the group theoretical framework of the Standard Model and was hoping for a more diluted answer. So I have come across this slide: ...
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204 views

Origin of quark masses

Does all the mass of the quarks in the standard model come from the Higgs sector or is there also a contribution to quark masses due to QCD chiral symmetry breaking?
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95 views

Why does the $Z$ boson not change quark flavour?

Is it just an observation from Particle Accelerators data? I was trying to understand what is it that mathematically stops the $Z$ boson from changing quark flavour, if it is known?
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57 views

Gluons, the Weak Force, or both?

I've recently been reading about how the Weak Force holds quarks together to make protons and neutrons. But before learning about that specifically, I found out about Quark-Gluon Plasma, leading me to ...
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Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?

I would be a little more restrained with the existence of antineutrons. First at all - if I understood right - the existence of antiquarks is hypothetical. If one not agree with this please refer to ...