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Questions tagged [quarks]

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

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Spaghettification on quarks?

Imagine a nucleon falls into a black hole, I would expect the gravitational force acting on each quark to be drastically different but due colour confinement wouldn't there more pairs of quarks being ...
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1answer
21 views

Muon neutrino interacting with nucleon's quarks

I'm considering the muon neutrino/anti-quark interaction with the nucleons of ice in the IceCube experiment. The purpose is to decide which antiquarks are $\bar{q}$ and $\bar{q}'$. I have the ...
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1answer
51 views

How do quarks keep themselves apart?

I was chatting with user Dan Yand regarding my recent question about colour charges, it was mentioned in the comment section that particles with colour charges attract each other like or unlike hence ...
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1answer
28 views

How does electron “orbit” nucleon unless 3 coloured charges act like positive charge?

Do quark(s) emit(s) electromagnetic wave otherwise how do(es) electron(s) form an orbital? Can colour charges somehow mimic electric charge? Btw I know quarks interact via strong nuclear force.
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How many anti/quarks can be squeezed inside a nucleon without upsetting exclusion principle?

I read about a nucleon with 3 Strange quarks which clearly violates PEP, however this was soon resolved by introducing colour charges. Then I read about colour confinement where surplus energy can be ...
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1answer
26 views

Muon neutrino and down quark interaction diagram

My questions concerns the IceCube experiment, in particular, the interaction between muon neutrino and the down quark. I've drawn the following Feynman diagrams: Are both diagrams correct? Can I say ...
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1answer
119 views

Temperature-dependence of quark potential in Abelian lattice gauge theory

I am working with Kapusta's "Finite-Temperature Field Theory" textbook, and am working through the first part of chapter 10. When building the correlator of the two quarks a distance $R$ apart in the ...
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2answers
137 views

If quarks can't be isolated in the first place, how did they become confined in the early universe?

On one hand, we know that quarks cannot exist in isolation. This is because the energy required to dissociate a quark-antiquark pair in a meson (or quarks in a hadron) will create a mesons (or hadrons)...
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1answer
54 views

Do antiquarks cancel quarks out?

I heard that antiquarks are just like antimatter. Does that mean that they cancel quarks out? If so, does that mean that there are more quarks than antiquarks?
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1answer
88 views

Commutator of a quark current

In Quantum Chromodynamics, when we take the limit in which the u, d and s quarks have no mass, there exists a global symmetry $G \equiv SU(3)_L \otimes SU(3)_R$ in flavour space. The corresponding ...
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1answer
65 views

Is a nucleus a collection of quarks or a collection of neutrons and protons? [duplicate]

I do not much about particle physics. But people say that neutron and proton are composed of quarks, and in turn a nucleus is composed of neutrons and protons. Therefore, the question is, is this ...
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1answer
50 views

The production of $b$ ($b$ bar) quarks

I have a question, please if there anyone helps me to understarnd how we distinguish the production pair of quarks $b$ ($b$ bar) it comes from a QCD background or comes from higgs decay?
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1answer
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A question about isospin of pion and kaon

In Ch.18 of the textbook An Introduction to Quantum Field Theory by Peskin and Schroeder, on P.611 when discussing QCD renormalization of the weak interaction, two operators ${\cal O}^{1/2}$ and ${\...
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1answer
109 views

Is the electroweak $SU(2)$ gauge symmetry an exact symmetry in Standard Model before spontaneous symmetry breaking?

In Standard model, components of a $SU(2)$ doublet (for example $u$ and $d$) have different masses. This means there is no $SU(2)$ symmetry, but I think it is okay because the $SU(2)$ symmetry is ...
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1answer
810 views

Is it a coincidence that quarks have exactly -1/3 or 2/3 the electron's charge? [duplicate]

I have read these questions: Why do quarks have a fractional charge? Is there an explanation for the 3:2:1 ratio between the electron, up and down quark electric charges? Hypercharge for $U(1)$ ...
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1answer
61 views

Coefficients of Color Potential in Quarks [duplicate]

I was wondering if there was a relation between the fractional coefficients $$2/3, 1/3$$ obtained when calculating color potential for quarks and the value of electric charge for the up and down quark....
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What is the experimental evidence that the nucleons are made up of three quarks?

What is the experimental evidence that the nucleons are made up of three quarks? What is the point of saying that nucleons are made of quarks when there are also gluons inside it?
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1answer
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what happens to positrons after pair production

what happens to positrons after pair production? There are two possible outcomes, but which one is true or most probable? The particle antiparticle pair have enough kinetic energy to overcome the ...
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2answers
119 views

When/ how were/are quarks formed?

We know that all particles can eventually be converted into energy. We know also that electrons were and still are formed by pair production from a 1MeV photon. Do physicists have yet any idea how ...
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1answer
95 views

Rho and Omega meson mixing

I am new to particle physics. So this might seem to be a trivial question. I read about $\omega$ and $\phi$ meson states being written in terms of octet and singlet state. In the same way, can $\...
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4answers
238 views

How can infinite density exist?

Thinking in mind, infinite density is where there is no space between particles correct me here if i'm wrong. Inside a blackhole at the core. So if there are 2 particles touching each other Then ...
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1answer
32 views

Fundamental and antifundamental representations, and hilbrt spaces

I am studying quarks $u$, $d$ and $s$. I know they can be represented by 3-vectors: We also have the antiquarks that are represented by the same 3-vectors: The difference between them is that when ...
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0answers
55 views

Wave function of two identical quarks

I'm asked to discuss what the ground state wave functions of $qq'Q$ would look like (a combination of two quarks and some spin 0 particle $Q$ which transforms like a singlet under flavor $SU(3)_F$ and ...
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1answer
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A question about the notation of the Standard model

The ${\rm SU(2)_L}$ doublets, for example, the left-handed quark doublets $Q_{iL}\equiv(u_{iL}, d_{iL})^T$ are assigned quantum numbers $(\textbf{3},\textbf{2})_{+1/6}$, which means $Q_{iL}$ are ...
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1answer
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What is meant by “the symmetry of an interaction”?

My understanding of a symmetry is this: apply an operation (e. g. parity inversion) to a system. If it behaves the same afterwards, it is symmetric under that operation. Now, quite often I see ...
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1answer
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How does Bhabha scattering imply the existence of quark/lepton substructure?

In the 1983 journal article New Tests for Quark and Lepton Substructure which covers some science and mathematics behind quark and lepton composition (theoretical). It says: Bhabha-scattering ...
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1answer
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Pulling quarks from one another creates a new pair of quarks? [duplicate]

It is said that the force between two quarks increases as they are pulled apart which is ultimately resisted by the strong nuclear force. Correct me if I'm wrong, but my physics teacher once said ...
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1answer
47 views

Deep inelastic scattering

Quarks can not observed directly in isolation so that they only can exist in the form of colorless hadron. So we may suggest some questions like "Is quark actually exist?", "Is it just mathematical ...
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Pion and quark mass

I would like to know why $$m^2_{\pi} \sim m_q$$ where $m_q = (m_u + m_d)/2$? Which values should I use to see that? I have used values from PDG and I do not see this equivalence. Could someone help me ...
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2answers
152 views

What makes strange quarks stranger than any other quark?

Back in the 1950s, physicists noticed that certain heavy particles (sigma baryons, lambda baryons, & K mesons) have significantly longer lifetimes than physicists originally predicted just based ...
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2answers
930 views

Is the Lagrangian in the Standard Model exact or approximate?

We say that the Standard Model has $SU(3)_{C} \otimes SU(2)_{L} \otimes U(1)_{Y}$ symmetries. However, the $SU(2)_{L}$ symmetry of the doublet ($u, d$) is not exact because $u$ and $d$ have different ...
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1answer
162 views

How did the three quarks ($u, d, s$) acquire different masses?

If the three quarks $u, d, s$ had the same mass, they would have an $SU(3)$ flavor symmetry ($u, d, s$). This symmetry is broken because these three quarks have acquired different masses through ...
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1answer
92 views

Why do the right-handed up quark and down quark not form an $SU(2)$ doublet?

The left-handed up quark and down quark are an $SU(2)$ doublet $(u, d)_{L}$. Why do their right-handed counterparts, right-handed up quark and down quark, not form an $SU(2)$ doublet $(u, d)_{R}$?
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Are There Reasonable Definitions Of The Pole Masses Of Light Quarks?

For the heavy quarks and charged leptons, the "pole mass" of a fundamental particle is its mass (which varies as a function of energy scale in the Standard Model) when the energy scale it is evaluated ...
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What is the symmetry of the doublet ($u$, $d$)?

The up quark $u$ and down quark $d$ form a doublet ($u$, $d$). I know that they have a SU(2) symmetry. However, they also have a U(1) symmetry because they are regarded as two states of the same type ...
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1answer
30 views

Is a quark‘s constituent mass affected by the chiral limit?

The up- and down quark’s constituent mass is usually taken to be around $300\,\text{MeV}\approx \tfrac{1}{3} m_\text{proton}$. Is this quantity affected by the chiral limit, where we let the quarks’ ...
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1answer
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How many elementary particles are contained in a molecule of $H_2O$?

I was wondering about how many elementary particles form up one molecule of $H_2O$. What I thought of is the following: Hydrogen : 0 neutrons, 1 electron, 1 proton; electron is elementary and proton ...
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1answer
51 views

A fourth (sterile) neutrino existence and quark generations

Would the existence of a fourth (sterile) neutrino imply the existence of a fourth generation of quarks and a fourth lepton, beyond electrons, muons and tau particles?
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1answer
216 views

Most trivial neutral pion decay

Literature states neutral pion decay by QED cannot occur directly because the pion is uncharged. However, I cannot see why Photons are not allowed to interact with the Quarks directly. Please ...
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76 views

Prove that the singlet state of 3 quark flavors is fully antisymmetric

I have three quark flavors, according to group theory: $$3\otimes3\otimes3=10\oplus8\oplus8\oplus1$$ I have to show that the 1 is antisymmentric. My idea would be to try to construct the states ...
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1answer
67 views

QCD from chirally segregated, gauged $SU(3)_L \times SU(3)_R$?

There are already theory papers out there in which color $SU(3)_C$ is actually the diagonal subgroup of multiple $SU(3)$ factors. But due to a comment by @zooby, a new twist on this idea occurred to ...
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Can quark-lepton mass be partially generated by Higgs?

In the Standard Model, quark-lepton masses are also generated by their couplings with the Higgs particle as the W, Z vector bosons are. Their masses are different because the Yukawwa couplings are ...
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1answer
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In inelastic scattering does the exchange photon interact with sea quarks?

In deep inelastic scattering between electon and proton, the electron emits a photon that interacts with a quark of the proton, which absorbs it. Then, in a second time, the quark interacts with the ...
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1answer
54 views

Do we actually know the charges of quarks? [duplicate]

It is well known that quarks have a charge of either 2/3e or -1/3e depending on quark. What is the evidence behind that? Did someone simply write $q_u+q_u+q_d=q_{proton}=1e$ and $q_u+q_d+q_d=q_{...
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1answer
130 views

Can we find a free gluon?

I have read these questions: Quark intrinsic angular momentum and the Proton Spin Crisis About free quarks and confinement https://en.wikipedia.org/wiki/Gluon And it made me curious. I understand ...
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1answer
47 views

Difference between boundedness (electrons around nuclei) and color confinement (quarks)

I have read these questions: How does the orbiting of electrons around nuclei START? Bound electrons don't move, right? Do different orbitals overlap in multielectron atom? What is the ...
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1answer
32 views

How does it make sense to talk about, for instance, quarks traveling at near lightspeed while confined to a volume as small as a proton?

How does it make sense to talk about, for instance, quarks traveling at near lightspeed while confined to a volume as small as a proton? The distances are so small, and the speed so high, that the ...
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Parton model: relation between $F_2(x)$ at fixed $Q^2$ and differential cross section as function of $x$

Consider deep inelastic scattering of electron on proton and parton model: $F_2(x)$ as a function of Bjorken $x$ at fixed $Q^2$ goes as in the following graph. The differential cross section is: $$\...
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0answers
37 views

What elements would be created by bombarding quark matter with neutrons?

Assuming we managed to find or create either Strange Quark Matter or UpDown Quark Matter, I've read the suggestion that it would be stable, but that bombarding it with neutrons would cause it to break ...
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1answer
52 views

Quark Transitions and Convservation of Energy

My question is essentially: How is conservation of energy held in quark transitions? Several quark transitions seem to break energy conservation, such as $$ d \rightarrow c W^{-}$$ $$d \rightarrow t ...