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

learn more… | top users | synonyms (1)

1
vote
1answer
13 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} : ...
12
votes
3answers
2k views

What does it mean that the neutral pion is a mixture of quarks?

The quark composition of the neutral pion ($\pi^0$) is $\frac{u\bar{u} - d\bar{d}}{\sqrt{2}}$. What does this actually mean? I think it's bizarre that a particle doesn't have a definite composition. ...
0
votes
0answers
48 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 ...
1
vote
1answer
52 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 ...
0
votes
0answers
7 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 ...
3
votes
2answers
140 views

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 ...
0
votes
1answer
20 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 $$s\overline{u}\rightarrow u\overline{u}+\overline{v_e}+e^{-}$$, ...
1
vote
1answer
27 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 ...
4
votes
3answers
1k views

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 ...
8
votes
3answers
2k views

Why do quarks have a fractional charge?

I am aware that evidence exists that strongly suggests the existence of quarks and do not doubt it. It is just simply really weird to me that they can have a fractional charge. While other ...
3
votes
1answer
67 views

String breaking in QCD

I have trouble understanding string breaking in QCD. I have read an article on arxiv (http://arxiv.org/abs/hep-lat/0505012), and I still don't understand what truly happens. My understanding of ...
1
vote
1answer
31 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 ...
0
votes
1answer
28 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 ...
1
vote
2answers
41 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 ...
13
votes
4answers
855 views

Origin of lepton/quark generations?

What theoretical explanations exist for the fact that there are three generations of leptons and quarks? I'm not so much asking why there are exactly 3 generations, but rather what makes electron, ...
5
votes
1answer
60 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 ...
5
votes
1answer
334 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 ...
2
votes
1answer
66 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 ...
4
votes
2answers
180 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?
2
votes
2answers
266 views

How does flux tubes between quarks bind them together?

If you have, say, a proton it has gluon field fluctuations around it. Those flux tubes between the quarks suppresses the gluon field fluctuations and create a true vacuum between them(correct me if ...
1
vote
1answer
534 views

What was the first discovery of the delta baryon $\Delta^{++}$?

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, ...
2
votes
1answer
35 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 ...
1
vote
1answer
99 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 ...
6
votes
2answers
167 views

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 ...
1
vote
3answers
115 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. ...
4
votes
2answers
110 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) ...
0
votes
1answer
97 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.
1
vote
1answer
64 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?
0
votes
1answer
53 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 ...
1
vote
0answers
26 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 ...
1
vote
0answers
20 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 ...
2
votes
5answers
602 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 ...
1
vote
0answers
118 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 ...
1
vote
0answers
34 views

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 ...
2
votes
0answers
22 views

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 ...
22
votes
4answers
2k views

Could the Periodic Table have been done using group theory?

These three questions are phrased as alternative-history questions, but my real intent is to understand better how well different modeling approaches fit the phenomena they are used to describe; see 1 ...
5
votes
4answers
1k views

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, ...
2
votes
2answers
319 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 ...
2
votes
1answer
66 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 ...
13
votes
2answers
3k views

Is it pions or gluons that mediate the strong force between nucleons?

From my recent experience teaching high school students I've found that they are taught that the strong force between nucleons is mediated by virtual-pion exchange, whereas between quarks it's gluons. ...
1
vote
1answer
103 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 ...
2
votes
2answers
51 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?
0
votes
1answer
109 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 ...
3
votes
0answers
50 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 ...
3
votes
2answers
652 views

Why there are no uuu and ddd baryons with spin 1/2?

What is preventing $Δ^{++}$ and $Δ^-$ baryons from going to a lower-energy state with spin 1/2 similar to that of protons and neutrons? I don't think the Pauli exclusion principle can prevent it ...
0
votes
1answer
41 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 ...
0
votes
1answer
42 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' ...
1
vote
0answers
61 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: ...
2
votes
1answer
85 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?
0
votes
1answer
48 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 ...