Questions tagged [quarks]

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

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What contributes most to the mass of the proton?

i'm a bit confused about the origin of the mass of the proton (or other hadrons). It is said that it stems from the renormalization of the current quarks, which have about 1/100 of the mass of the ...
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Symmetric and Antisymmetric states for 3 Quarks

I think we suppose to have 27 states if we are talking about three quarks. can anyone explain to me how to identify the symmetric states and antisymmetric ones ? or even a keyword in which I use it to ...
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How are the constituent quark masses determined?

I was wondering how the constituent quark masses are determined (in wikipedia they claim $m_{u/d,const}\approx 350 $ MeV), but how is this in practise determined or estimated? I could not find any ...
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Why does isospin symmetry survive chiral symmetry breaking?

In QCD there is a breaking of chiral symmetry such that, for the lightest quarks only, we have $$\langle \overline{u} u \rangle = \langle \overline{d} d \rangle = \mathrm{const.}$$ where the constant ...
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Why is there a $u$ in the middle of the feynman diagram for a quark and an antiquark annihilating?

There is a feynman diagram in chapter 2 of Griffiths Introduction to elementary particles, where a pair annihilation is taking place. I am confused as before it was written that internal lines are ...
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Could the values of the CKM matrix be determined from the quark masses?

It seems like the values of the CKM matrix are somewhat related to the masses of the quarks. For example, the heavier the quark the less likely it is to change into another quark in a weak interaction....
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Why can't $uus$ and $uds$ quark content have $I = 1$ Isospin?

Well, I know the isospin singlet with $I=0$ and isospin triplet with $I = 1$. But for $I = 0$, why it must be $uds$ quark content rather than other assembly like $uus$ or $dds$? $ud$ can have $I = 0$ ...
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CKM Matrix Magnitude Question - Top to Bottom Greater than One?

In the CKM Matrix article on Wikipedia, the "standard" parameters for each matrix element are written with combinations of sines, cosines, and a complex exponential of 4 angle values. Using ...
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What is a polarized/unpolarized parton?

In QCD physics, certain partonic distributions like Generalized Parton Distributions (GPDs) and Transverse Momentum Distributions (TMDs) are defined for the case where the parton is either unpolarized,...
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Which hadrons were present after the phase transition from the post-Big Bang QGP?

This question relates to the "hadron epoch" (after the initial quark-gluon plasma, but before the end of baryogenesis). My understanding is that the phase transition that ends the quark-...
SgtJohn74's user avatar
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Why, in QCD, are quarks in the fundamental representation of $SU(3)$?

QCD is built from the notion that Dirac's Lagrangian should be invariant under gauge colour transformations. Here, quarks are elements of $\psi_{\alpha,f,c}(x)$, where $\alpha$, $f$ and $c$ stand for ...
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Justifying the identification of eight gluons with the ${\bf 8}$ from ${\bf 3}\otimes{\bf 3}^*$

When we combine the fundamental ${\bf 3}$ and antifundamental ${\bf 3}^*$ of color $SU(3)$ of QCD i.e. single quark of three colors and a single antiquark of 3 anticolors, nine states are obtained. ...
Solidification's user avatar
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Comprehensive references to learn about the flavor $SU(3)$ model of hadron classification

What are some comprehensive references to learn about the flavor $SU(3)$ model of hadron classification based on group theory? Textbooks, Lecture notes, videos anything will do. I need to learn this. ...
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Can a sea quark swap places with a valence quark within a proton?

I understand that a proton is composed of three valence quarks and a very large number of sea quarks that briefly come into existence and then annihilate as quark-antiquark pairs. Is it possible for ...
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Would a black hole's event horizon split up a hadron into it's constituant quarks? Therefore creating free quarks?

As a thought experiment, say, for the sake of simplicity, we have a meson. This meson, which is traveling near light speed, is traveling towards a black hole. And skirts the event horizon in such a ...
Colonizor48's user avatar
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Color vectors for antiquarks

For a single quark, the colour vectors are given by $$r=\begin{pmatrix} 1 \\ 0 \\0 \end{pmatrix} \qquad g=\begin{pmatrix} 0 \\ 1 \\ 0 \end{pmatrix} \qquad b=\begin{pmatrix} 0 \\ 0 \\ 1 \end{pmatrix}$$ ...
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Why are vector mesons heavier than pseudoscalar mesons?

From the hyperfine calculation we find that the mass of the vector mesons are heavier than pseudoscalar meson, as the following proves. The magnetic moment is proportional to the spin and inversely ...
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Octet and decuplet baryon wavefunction

I read the octet and decuplet baryons symmetric and anti-symmetric wavefunction from 'Riazzudin and Fiazzudin's book. But I am little confused about the wavefunction of neutral sigma and Lambda baryon....
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Mass of $B$ Meson

This is a question from Griffith's Introduction to Elementary Particles, Chapter 2: The upsilon meson, $b\bar b$, is the bottom-quark analog to the $\psi$, $c\bar c$. Its mass is 9460 MeV/$c^2$ and ...
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How do I numerically compute the interquark potential from the correlation function of Polyakov Loops?

I know that the potential can be calculated in the following way: $$ aV(r) =-\ln(<\sum_{\textbf{x}} (P(\textbf{x}+R)P^{\dagger}(\textbf{x}))>)/N_T. $$ Now, suppone I have some procudure to ...
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Is there something special about the $b$ quark?

I have seen many papers about measurements related to $b$ quarks, for example the forward-backward asymmetry of the $b$ quark or the decay width of $Z$ to $b \bar b$ pairs, but not so many for the ...
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Baryon wavefunctions

The textbook I am currently using states that when all quarks have the same flavor, there are no $J=1/2$ baryon wavefunctions for the ground state $l=0$. Is this an experimental result or is there a ...
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'Elementary' particles (electrons) vs non-elementary particles (protons) regarding relativistic mass

Is there a possible slight difference between protons and electrons behaviour while they are accelerated at speeds that cause relativistic changes to their mass. Why am I asking that? Because for a ...
Krešimir Bradvica's user avatar
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$J=1/2$ and $J=3/2$ Baryons with $uds$ quarks

Why are there two different $J = \frac{1}{2}$ baryons with quark content $uds$ (the $\Lambda_{0}$ and $\Sigma_{0}$) but only one $J = \frac{3}{2}$ baryon (the $Σ_{*,0}$) with the same quark content? I ...
Archie C's user avatar
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Matter-antimatter conversion in quarks

If in beta plus decay, regular matter such as the up quark can decay into a positron, I have to wonder under high pressure, could it be possible for a quark to decay into the antiquark of its opposite?...
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Relation between (Anti-) Quark-Gluon-Quark Correlators

I'm having trouble in understanding the derivation for the realtion between Antiquark-Gluon-Quark and Quark-Gluon-Quark correlators given in a PhD thesis which I sadly can't find a link of to share ...
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Quark structure of Baryons

I was studying Particle Physics then suddenly I came up with a question that why only Baryons are made up of three quarks, at first I thought to to conserve Baryon number which is $\frac{1}{3}$ for ...
Bishal Sarkar's user avatar
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Could a fourth family of quarks and leptons account for dark matter?

In the early universe, could a family of quarks and leptons have formed an electrically neutral particle that is dark matter?
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What is the interaction between electrons and the electromagnetic field to give them charge?

*What is the interaction between a particle, like an electron, with the electromagnetic field that causes that particle to be charged? for example. If the positive charge of a proton comes from the ...
Jackson Wallace's user avatar
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How can a meson beam be created?

I was reading this thread where the answer states that to use deep inelastic scattering on mesons, we have to "generate a meson beam (which is a bit of a trick in and of itself) and direct it ...
Jungwoon Song's user avatar
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How do scientists attempt to break quark confinement?

From what I understand, when energy is supplied to quarks, it elongates the gluon tube and when enough energy is put in, new quarks are formed, keeping quark confinement. However, I am inquisitive ...
Jungwoon Song's user avatar
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How Does QCD Explain Nuclear Fission?

This question is brief and simple. As a layman, it is my understanding that QCD (Quantum Chromodynamics) explains the nuclear force as a "residual" force, mediated by pions (mesons), which ...
muldrowhanif's user avatar
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Interaction between an electron and an antiproton

I have read in many sources that particles and their respective antiparticles annihilate, but a particle and another particle's antiparticle (for example, an electron and an antiproton) do not. ...
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Does loss of momentum in quarks account for mass defect?

I'm trying to conceptualize the mechanism of which the quarks of the baryons and mesons themselves lose energy due to binding energy. Traditionally, mass defect is explained as the net energy released ...
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Is there any way to think of Quarks in a baryon with Clebsch-Gordan coefficients?

I'm wondering if this idea is as un-natural as it feels in my head. My understanding of CGC's is that I have various fractional spin states like: $$ \text{particle 1:} \ |j_1=\frac12, m_2=\frac12,-\...
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Are all elementary particles consequential?

Apologies if the title is misleading. Really what I'm curious about is if every elementary has a point, at least in what we know. I know the different types of quarks are important of course, as they ...
SCPirate's user avatar
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How to write a naive Dirac matrix for Lattice QCD?

I'm trying to write down the naive Dirac matrix (with fermion doubling) for a LQCD simulation with one quark, for now. I initialized the $SU(3)$ gauge field and the quark field. The quak field has 4 ...
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How do I rule out the decay $dss \to n + \pi^{-1}$?

I recently saw a question: A baryon has quark structure $dss$ and it decays via the weak interaction. Which of the following is a possible decay product? $\Lambda^0+\pi^{-1}$ $n + \pi^{-1}$ $\Lambda^...
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How to use Cabbibo matrix to infer the corect $\sin/\cos$ factor in weak interactions involving quarks?

If we have the fact that $|u> --> |d'>$ and $|c> --> |s'>$ are the only allowed transitions for 2-family charged current weak interactions, and we can relate the mass eigenstates |d&...
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Superposition of charge states in the Neutral Pion

The quarks of neutral pions don't exist in a pure flavour state, and instead are described as a superposition of up-antiup with down-antidown: $\frac{u\bar{u}-d\bar{d}}{\sqrt{2}}$ However up and down ...
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Yukawa coupling to the top quark and superstring theories

Can superstring theory give a good reason of why the Yukawa coupling to the top quark is almost "natural" while the remaining leptons and quarks have negligible couplings to the Higgs? I ...
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Why $\pi^+$ meson possible combinations of quarks is only three?

I am a starter at nuclear and particles physics. I am reading particles and nuclei an introduction to the physical concepts. There was a paragraph about Colour-neutral particles and how only ...
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Construction of the wave function of $D$ mesons

The $D^{\ast+}$ meson can decay as $D^0+\pi^+$ or as $D^++\pi^0$. It is a vector meson, therefore having $J^P=1^-$. Furthermore, $D^+$ is made of $c\overline d$ and $D^0$ of $c\overline u$. The ...
Giovanni Gravili's user avatar
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2 answers
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Why are protons/neutrons spin-$\frac{1}{2}$ when they are made up of three valence quarks (also spin-$\frac{1}{2}$)?

If we take the composite angular momentum of the three valence quarks, we should have a proton/neutron spin angular momentum of, $$S=\{ \frac{1}{2},\frac{3}{2} \}$$ using the general rule for adding ...
Adrien Amour's user avatar
2 votes
1 answer
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Do Neutron stars have free quarks?

Do Neutron stars have free quarks? Also Can Quark Stars be formed also due to this reason? Because of Asymptotic freedom high energy causes quarks to be free but according to the mass-energy ...
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3 answers
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Do protons have a shape?

They are often assumed to be balls and spheres in high school textbooks and exams and I had never questioned this until somebody complained to me that modern physicists are obsessed with balls. Do ...
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How many multiquark stable (or metastable) and observable states are there in QCD and the SM?

I was wondering about the last news about multiquark resonances. We get some tetraquark and pentaquark states...But, why to stop there? Could we have long-lived enough hexaquarks, heptaquarks, ...
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$W$ coupling to excited quarks

Can a $W$ couple to both left-handed and right-handed excited quarks? I think this paper says that is true of the $W’$ (https://doi.org/10.1016/j.physletb.2011.03.066). And I think this article says ...
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Virtual Quarks Inside the Proton

I just watched a video that claims that the standard 2U and 1D quark inside a proton is too simplistic. Basically the quarks inside are virtual quarks, that are constantly changing. There are times ...
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Detection of quarks, gluons and color charges in quark-gluon plasma?

Due to quark confinement and color charge neutrality, individual quarks and gluons are non-observable under ordinary circumstances. However, under extreme temperature achieved by colliding Pb+Pb ...
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