Questions tagged [quarks]

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

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1answer
117 views

Simple “toy-model”-like explanation of quark confinement (QCD) and accompanying math

I have a qualitative understanding of quantum chromodynamics within nucleons and between nucleons, but I do not understand the math behind some of the physics like quark confinement. What is the math ...
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1answer
81 views

Why protons are stable but Neutrons not?

just read something about standard model and find it very interesting, proton is made of there subatomic particle U,U,D and neutron have U,D,D . electromagnetic force between U,U,D wants to rip apart ...
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Has a 3D chart of nuclides ever been published or proposed $(N, Z, S)$? What information might it show?

Phys.org's 'Strange' glimpse into neutron stars and symmetry violation leads to the new Nature Physics Letter Measurement of the mass difference and the binding energy of the hypertriton and ...
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How is Einstein-Bose condensation supposed to stabilize d*(2380)?

A recent paper suggests a new dark matter candidate: Einstein-Bose condensates of the hexaquark/dibaryon d*(2380) ($uuuddd$). The nice thing about this theory is that it does not require any new ...
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Understanding interaction between two quarks

Two protons and two electrons repel each other as they have same charge. Protons and electrons attract each other since they are oppositely charged. A single proton is made up of two up and one down ...
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Why does the term $i\epsilon^{\alpha\mu\beta\nu}p_{\alpha}q_{\beta}$ vanish in the squared amplitude of the top decay?

I would like to calculate the squared of the amplitude of a top-decay $t-> Wb$. I know already the solution, but I can't get there: I get stuck with the Levi-Civita-Tensor on my way. Can you help ...
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39 views

Quark confinement mechanism

As far as I understood: Quark confinement states that observing individual quarks is not possible, color charged quarks are confined into hadrons. As we try to pull them apart, force between them ...
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1answer
44 views

What would the propagator of the Feynamn diagram for $\bar{q}q \to \gamma \gamma$ be?

I am trying to draw the Feynman diagram at tree-level for: $$\bar{q}q \to \gamma\gamma $$ but I don't seem to understand what sort of propagator fits this diagram? I have seen in some places that a ...
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What is quark 'confinement' in the context of Yang-Mills Theory?

In the context of Yang Mills Theory, what is quark confinement? Please try to explain as simple as possible (obviously without being too general)
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How do I show that the tensor product of $\mathbf{3} \otimes \mathbf{\bar{3}}=\mathbf{1} \oplus \mathbf{8}$? [duplicate]

It's often stated that the tensor product of the representations of $SU(3)$ satisfies $\mathbf{3} \otimes \mathbf{\bar{3}}=\mathbf{1} \oplus \mathbf{8}$, and that this implies that if flavour $SU(3)$ ...
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If quarks change colours constantly how are proton and neutron stable relatively?

Say for example a proton is composed of Up, Up and Down (valance) quarks and suppose the Down quark absorbs a gluon, Down quark must change colour in order to conserve colour charges but so must the ...
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51 views

Is there a neutral current interaction between an antineutrino and an anti-strange quark?

I'm doing some revision for an exam and was wondering what the Feynman diagram for a charged current interaction between an antistrange quark - residing in a proton - and an incoming antineutrino ...
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Can quark tunnel out and if so where do the energy used to form new meson come from? [closed]

If we give a quark enough energy to pull it out of a proton the energy can then creates more quarks but what happens if the quark quantum tunnel out, is it possible or the potential is simply too big ...
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Why is a quarkonium any different from a meson?

Quarkonium states are bound states of a quark-antiquark pair but so do the mesons. What is the difference between a quarkonium (e.g., charmonium, and bottomonium) and a meson then? Why use a separate ...
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Do Quarks violate the law of energy conservation?

Look, I am not too knowledgeable in this area, but all I know is the following. So please bare with me. Idea Since Quarks are always in pairs and are bonded together by the Strong Force and cannot ...
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1answer
82 views

What's the definition of $\bar\psi$ in QCD?

This is a two part question. What is the definition of $\bar\psi$ in QCD? In QED I know that $\bar\psi=\psi^\dagger\gamma^0$, but in QCD we also have flavor and/or color space. In particular, I'm ...
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Why do Fermions (quarks specifically) have transversity while Bosons (gluons specifically) don't? [duplicate]

I hope this question isn't naive or anything of the sort but I am relatively new to this topic and this is the first question I ask on here. The Collins asymmetry which is exclusively a quark-...
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43 views

How do gluons bind the quarks together within the hadrons and mesons?

I was trying to know about the strong nuclear force within the nucleus and the books and websites told me that it is the gluons which carry the force, and now I am curious how the gluons carry this ...
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Quark Chirality Constraints in Nucleons

SW Engr here educating myself on particle physics, apologies in advance for any phrasing errors. I tried the google machine to no avail. Q: If only left handed matter fermions experience the weak ...
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4answers
103 views

Where do the mass and volume of the two quarks go when they create a meson?

A quark and an antiquark are fermionic particles with mass. Where do this said mass go when they bind to create a meson? If there's annihilation at play, how do mesons even be in the first place? ...
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1answer
62 views

Why can the masses of the Higgs and top quark determine whether we live in a false vacuum?

I read in the paper linked below that the ground state of the universe depends on the potential of the Higgs field, particularly the graph of the Higgs potential with its minima and maxima. I think I ...
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1answer
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How do you reconcile quark masses with notion of confinement?

In trying to understand exactly what confinement means, I have been reading 't Hooft s original paper on 2D QCD at large $N$. In the paper he shows that the quark propagator pole is moved to infinity, ...
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Is there a reason, other than mass hierarchy, that we associate each quark generation with a particular lepton generation?

The Standard Model contains three generations of quarks, and three generations of leptons. We generally pair off these generations into the "light" generation ($e, \nu_e, u, d$), the "medium" ...
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Quark-antiquark plasma and Fermi-Dirac statistics

I'm attempting to work my way through the following set of question: a) A plasma consists of an equilibrium mixture at temperature $T$ of quarks, $q$, (massless,relativistic, spin $\frac{1}{2}$, ...
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81 views

Why do this meson state (consisting with $ u,s,d$) are acceptable by nature?

I am new in Particle Physics and try to understand "Quark-Antiquark States:Meson article in Quarks & Leptons by Halzen and Martin(p=46) Why do this meson states are are acceptable by nature $$A=\...
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What was above and below the QCD chiral symmetry breaking temperature?

Above a critical temperature in the Universe, there was probably a phase of unbroken approximate QCD chiral symmetry. Mathematically, the symmetry breaking is triggered when the operators $\bar{\psi}{\...
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Why aren't Delta and Omega particles stable?

Not only are they not stable their half-life is in the nanoseconds. Why are they so different from protons?
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Why don't hadrons form from quarks of all the same charge?

Why don't Hadrons ever form from quarks of all the same charge? For instance you never see 2 or 3 up quarks together with no down quarks or vice-versa.
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Quark Model Family

I have studied the baryon J=1/2 family.i did the $(Y,I_3) $ diagram and started from the highest weight $(\frac{1} {2} ,\frac{\sqrt{3} }{2}) $ which is the proton and used the operators $I_{+-} \ \ U_{...
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How would a quark star maintain degeneracy near the surface?

I'm still not exactly understanding how a quark star could possibly exist for more than a fraction of a second. Neutron stars are already hypothesized to have degenerate quark matter at their cores, ...
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Does quarks always pulls each other?

Pions consist of quark and antiquark and strong force keeps them together. So color charge and anticolor charge attracts each other. But in proton we have 3 quarks and they also attract each other. It ...
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1answer
135 views

Why do the $c$, $b$ & $t$ quarks have strong hypercharge?

From the $SU(3)$ flavour symmetry we have quantum numbers for the up, down and strange quark, associated with the Eigenvalues of the Gell-Mann matrices $\lambda_3$ and $\lambda_8$. Namely $\lambda_3$ ...
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1answer
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If a particle and its antiparticle annihilate upon contact, how do they form bound states?

I am reading about some old discoveries in particle physics and early collider experiments from Perkin's Introduction to High Energy Physics. However, I didn't get the answers to all my questions. If ...
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79 views

How experiments differentiate between valence quarks and sea quarks

The picture that baryon consist of three quarks and mesons consist of a quark,anti-quark pair is inaccurate.However this simple picture is enough to explain many properties of the hadrons as mentioned ...
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$SU(3)$ $U$ and $V$ spin normalization

As we know the $SU(3)$ algebra can be written in terms of $3$ dependent $SU(2)$ algebras viz $(T_+,T_-,T_3),(U_+,U_-,U_3)$ and $(V_+,V_-,V_3)$. There action on a standard state is $\mid T_3,Y\rangle$ ...
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1answer
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Could electric dipoles within hadrons provide an alternate explanation for strong force? [closed]

We all know that hadrons such as proton and neutrons are made up of quarks and not all of the quarks have the same charge. This would suggest that they have a positive and negative side. In the case ...
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1answer
143 views

Why do we still call the electron charge the elementary (EM) charge?

The electron is an elementary particle, part of the SM, pointlike, with no substructure, or spatial extent. Its intrinsic properties include its EM charge, which we still call the elementary charge. ...
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How can electrons and quarks be composite?

There are theories suggesting that the electrons and quarks are not elementary particles, but instead are composite particles of two or more yet undiscovered elementary particles. However ...
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Why is color change between quarks without consequence?

As always I will preface this question with the fact that I only have a high school education, so I may be overlooking something, or unaware of something that is inherent to the question. That being ...
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1answer
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Why did scientists find fractional particles in the experiment of particle collision?

Quarks can’t be isolated because of the quark confinement. Then why did physics observe particles with fractional charge coming out in the experiment of deep inelastic scattering? Gluons are the ...
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Deriving relation between pole and running quark masses

How do I compute quark self energy and use it in order to derive detailed relation between pole and running quark mass? If I do it for one loop, I should use this for running mass: $\mu^2\times\...
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Alternative symmetric spin + flavor part of a proton?

I have a doubt about the proton's quark structure. All sources I've read agree that the following is the quark structure of the spin-up proton (this one is from Griffiths' Introduction to Elementary ...
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A bilinear form or a dot product $X \cdot Y$ of emission X and absorpion Y of a vector boson W in the context of transformation of quark flavors

The reason for this question is related to the fact that I think something is missing when an absorpion and emission of a (intermediate) vector boson $W$ in the context of transformation of quark ...
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Why do quarks flip chirality when exchanging an instanton?

Quarks are elementary particles, part of the SM. There are a lot of different questions and answers on this site about chirality, I did not find a really good description, so I will use this wiki ...
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Hadronization in a collider

Say, in a collision, do the quarks need to first hadronize to pions? Or is there a probability that they can hadronize directly to heavier particles like the charm quarks.(quark-anti-quark pair) The ...
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Is there any time dilation in between quarks or nucleons?

Mass curves spacetime creating a gravitational gradient/time dilation, and mass is mostly energy when considering the miniscule mass of the quarks themselves. This implies that the dilation is caused ...
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How are the structure functions in Deep inelastic scattering measured?

I've been reading lots of different textbooks on the parton model and deep inelastic scattering and the discovery of quarks, and most of the time whenever I see a plot, it's about the measurement of ...
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3answers
173 views

When are W-bosons emitted?

According to this Wikipedia page W-bosons are involved in beta decay. According to Wikipedia, this occurs when a down quark turns into an up quark and also emits a W− boson. When this happens in a ...
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A question about quarks and quantum chromodynamics

Penrose writes the following on pg 648 of his book "Road to Reality" How can we treat quarks as real particles, if they have the wrong spin-statistics relation? The way that this problem is dealt ...
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1answer
143 views

Why is it that the Callan-Gross relation predicts that quark has spin 1/2?

I'm studying deep inelastic scattering, and currently at the part where they say the Callan-Gross relation: $$F_1 (x) = \frac{1}{2x} F_x (x)$$ where $F_1$ and $F_2$ are the dimensionless structure ...

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