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Questions tagged [quarks]

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

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

There are three generations of quarks and two types in generation. Their interaction through the strong force constructs hadrons. The study of the strong interaction of quarks and gluons belongs to , and of course, the (which includes QCD).

Quarks are .

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What's inside a proton?

What constitutes protons? When I see pictures, I can't understand. Protons are made of quarks, but some say that they are made of 99% empty space. Also, in this illustration from Wikipedia, what's between the quarks?
MyFavouritePhysicistIsNewtax
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Why do electron and proton have the same but opposite electric charge?

What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of photon field, but is this explanation enough? Do…
Newman
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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. They are not, however, taught anything about…
qftme
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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?
Solidification
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Is there any current technology that depends upon a deep understanding of quarks?

I think the title about says it all. If someone asks me "What good is the Theory of General Relativity?" (or what did Einstein do that was so great, or whatever) My pat answer is, "You use GPS right? Well, GPS requires knowing the location (in…
John
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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 below for more discussion of that point. Short…
Terry Bollinger
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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" generation ($\mu, \nu_\mu, c, s$), and the "heavy"…
Michael Seifert
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How (or when) do gluons change the color of a quark?

I know a baryon is only stable when it contains a quark of each color. And as far as I know, the gluon essentially changes the color of a quark and moves onto the next, and this is what holds the particles together. But in the process of the gluon…
Vedvart1
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Why isn't there a second baryon octet?

Let's temporarily ignore spin. If 3 denotes the standard representation of $SU(3)_F$, 1 the trivial rep, 8 the adjoint rep and 10 the symmetric cube, then it's well-known that $$ 3 \otimes 3 \otimes 3 = 1 \oplus 8 \oplus 8 \oplus 10.$$ Interpreting…
Evans
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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 elementary particles, such as the electron, carry an…
Christopher S
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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. There's a difference of 2 MeV between the quark…
Kasper
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How to determine the mass of a quark?

As far as I know quarks are never found in isolation, so how can we determine their rest mass?
pipsi
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Proton: 2 up, 1 down quark, Neutron: 2 down, 1 up, how can Neutron: proton + electron?

I imagine that there is a pretty simple answer to my question, but I have just never gotten it straight. If a proton is comprised of two up quarks and a down, and neutrons are comprised of two down and an up, how can a neutron be a proton and…
M. Lumsdaine
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How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content?

Title says it all: How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content? Doesn't this make them the same baryon?
spraff
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Neutrino oscillations versus CKM quark mixing

I wish to describe in simple but correct terms the analogy between the Cabibbo–Kobayashi–Maskawa (CKM) and Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrices. The CKM matrix describes the rotation between weak interaction eigenmodes and the flavour…
Slaviks
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