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

learn more… | top users | synonyms (1)

33
votes
4answers
13k views

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 ...
10
votes
2answers
2k views

About free quarks and confinement

I simply know that a single free quark does not exist. What is the reason that we can not get a free quark? If we can't get a free quark then what is single-top-quark?
68
votes
8answers
27k views

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 ...
12
votes
4answers
28k views

What are quarks made of?

So atoms are formed from protons and neutrons, which are formed from quarks. But where do these quarks come from? What makes them?
7
votes
2answers
686 views

How quark electric charge directly have been measured?

How quarks electric charge directly have been measured when quarks never directly observed in isolation? (Due to a phenomenon known as color confinement.)
19
votes
4answers
7k 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. ...
5
votes
1answer
426 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 ...
5
votes
2answers
859 views

Quarks in a hadron- where does the mass come from

We know that the sum of the masses of the quarks in a proton is approximately $9.4^{+1.9}_{-1.3}~\text{MeV}/c^2$, whereas the mass of a proton is $\approx931~\text{MeV}/c^2$. This extra mass is ...
1
vote
1answer
7k views

Why isn't Hydrogen's electron pulled into the nucleus? [duplicate]

Possible Duplicate: Why do electrons occupy the space around nuclei, and not collide with them? Why don’t electrons crash into the nuclei they “orbit”? From what I learned in chemistry, the ...
10
votes
2answers
1k views

Neutrino oscillations versus CMK quark mixing

I wish to describe in simple but correct terms the analogy between the Cabibbo–Kobayashi–Maskawa (CMK) and Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrices. The CMK matrix describes the rotation ...
9
votes
3answers
4k 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 ...
2
votes
1answer
3k views

Quark Radius Upper Bound

If quarks had internal structure (contradicting current beliefs), what is the lowest upper bound on their "radius" based on current experimental results? If possible, I'd prefer to only consider ...
25
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 ...
14
votes
4answers
1k 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, ...
6
votes
2answers
267 views

Why do quarks tend to bond in groups of three?

Why do quarks tend to bond in groups of three? I understand why they might in bond in groups of three to create a net charge of zero (i.e. neutrons), but I don't understand why they form protons and ...
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, ...
-11
votes
2answers
2k views

Could the fractional model of Quarks electric charge turn out to be false? [closed]

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, +...
8
votes
1answer
785 views

Do color-neutral gluons exist?

If I'm correct a quark can change color by emitting a gluon. For example a blue up quark $u_b$ can change into a red up quark by emitting a gluon: $$u_b \longrightarrow u_r + g_{b\overline{r}}$$ (Here,...
6
votes
1answer
131 views

Can coherent superpositions of a neutron and antineutron exist?

In my recent post I learned that electric charge is always conserved in contrast to strangeness quantum number, which limits the types of Hadrons that can be build. Furthermore, also different masses ...
3
votes
2answers
79 views

Why do particle physicists use the $h\rightarrow{\gamma\gamma}$ decay mode rather than $h\rightarrow{b\bar{b}}$?

Just wondering, the $h\rightarrow{\gamma\gamma}$ decay mode is often quoted as being most sensitive to measuring the mass of the Higgs particle, why isn't the $h\rightarrow{b\bar{b}}$ decay channel ...
6
votes
1answer
2k views

Why are there 3 quarks in a proton? [closed]

A few quark related questions (I don't know much about them other than that there are 2 flavors concerning protons and neutrons). Why are there 3 quarks in a proton or neutron? Why not 2 or 4? Is ...
5
votes
1answer
273 views

Is there a tb meson?

I was wandering around the particle date group page for meson and couldn't find a meson for top-bottom, which from symmetry you would expect. Q1: Is this because it hasn't been found? Q2: There is ...
5
votes
1answer
1k views

How does Delta baryon decay conserve angular momentum?

I'm a chemist so bear with me: I understand the Delta baryons $\Delta^{+}$ and $\Delta^{0}$ to be in some sense spin (and isospin) quartet states of the proton and neutron. These can decay straight ...
0
votes
1answer
38 views

Quark, antiquark pair doubts [closed]

When Quark, antiuquark pair is created by high energy photons, they glue togheter as mésons or another pair is created to combine they, totalizing four particles?
13
votes
1answer
1k views

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?
12
votes
3answers
4k 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. ...
7
votes
2answers
259 views

Could a tetraquark $q \bar{q} q \bar{q}$ be colorless?

CERN just posted this article where it informs that it was found an hadron which cannot be classified within the traditional quark model. What other models are there to explain this result? Or is it ...
4
votes
2answers
261 views

How can a pion have a mass, given it's a “field mediator” and created/destroyed continuously?

Maybe some of my assumptions here are basically wrong, but isn't it true that pion is the "mediator" for the strong force field. the quantum field theory basically says that there are no fields, ...
2
votes
5answers
869 views

Could Quark model turn out to be false?

Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks ...
9
votes
2answers
2k views

What IS Color Charge?

This question has been asked twice already, with very detailed answers. After reading those answers, I am left with one more question: what is color charge? It has nothing to do with colored light, ...
8
votes
1answer
251 views

Upper Mass Limit of Quark Stars

While there is no confirmation that quark stars exist, is there any theoretical limit analogous to (but different from) the Tolman–Oppenheimer–Volkoff limit for neutron stars? In other words, what is ...
5
votes
2answers
231 views

Dirac magnetic monopoles and quark fractional electric charge quantization

When applying the Dirac quantization rule for electric and magnetic charge, I assume one is considering unit electric charges such as electrons. How does the Dirac quantization rule apply for the ...
4
votes
2answers
226 views

Can quarks be considered real and elementary?

In our current theories all hadrons are made up of quarks and gluons. This view reduces considerably the big family of hadrons by providing a very logical structure in which all quantum properties ...
4
votes
1answer
362 views

Why isn't the quark charge taken as primitive?

Why are electrons taken implicitly to be the elementary charge? It would save a lot of fractions in particle physics problems.
5
votes
1answer
161 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 ...
4
votes
1answer
231 views

Electron Charge is 150%?

Is there a theory for why the charge of an electron is precisely 50% larger (magnitude) than a quark's? I have usually thought of this the other way around: the charge of a quark being 2/3 (or -2/3) ...
1
vote
1answer
56 views

Changing, or static, quark color composition within a proton?

Consider say the proton. It is seems to be universally stated that a proton is "composed of three quarks, 2 up and a down, and you must have the three different 'colors'". So, you can have blue-up, ...
1
vote
1answer
225 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 ...
1
vote
2answers
96 views

Quarks are now considered to be fundamentals, but so were atoms some time ago. So the way we see is only limited by our technological advances? [duplicate]

After watching this FuseSchool - Global Education episode, I cannot stop thinking how can something not have a substructure, how it cannot be split? http://www.youtube.com/watch?v=nlv06lSAC7c
1
vote
3answers
724 views

Anti-neutrons, anti-quarks, isospin: What is observed and what is derived?

I would be a little more restrained with the existence of antineutrons. First at all - if I understood right - the existence of antiquarks is hypothetical. If one not agree with this please refer to ...
9
votes
2answers
484 views

Possible implications of Tetraquark/Quark Quartet

Today on Nature's website appeared a news about the discovery of a quark quartet (formed from two quarks and two antiquarks). They say that this particle containing four quarks is confirmed. This is ...
7
votes
1answer
88 views

Strong force between quarks that are out of causal contact

This is a rather artificial scenario, but it has been bugging me lately. Background Due to the confinement in QCD, quarks are bound in color-neutral configurations. Any attempt to separate a quark ...
5
votes
3answers
244 views

The Makeup of the Pentaquark

Why is it that when they have the artist's rendition of the Pentaquark it shows two downs, two ups, and one anti-strange quark? Is this or is this just for show? Follow up to this question: if this ...
3
votes
0answers
58 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 ...
2
votes
1answer
64 views

Evidence for standard model description of neutrons

as I don't know too much about experiments I have the following question concerning the evidence about the quark constituents in neutrons. After a quick google investigation I found some sentences ...
0
votes
1answer
1k views

What is the relationship between the Higgs field and quarks?

I have some difficulty considering the relative size of each and the meaning behind the shape of Higgs boson. I ask relating to the structures of both the Higgs field and quarks. How is it that the ...
0
votes
1answer
42 views

Spatial configuration of quarks?

Is there anything known about the spatial configuration of the quarks within a proton of pion? Or are they just considered to be two or three overlapping points?
0
votes
1answer
79 views

What maximum energy can be stored in a gluon field flux tube

Question is as clear as stated in title. What is the maximum energy that can be stored in a gluon field flux tube without production of an quark anti-quark pair? And how much it usually store in a ...
0
votes
1answer
102 views

If one is talking about antineutron production, what is the charge exchange?

In this question was given the antineutron production in the way $$ p + \bar{p} \rightarrow n + \bar{n}. $$ Internet search gives one source only where the charge exchange is mentioned. They talk ...
-2
votes
1answer
605 views

Why aren't quarks free? [duplicate]

According to latest modern theory on subatomic particles, electrons and protons are further divided into quarks, having fractional charges. My question is, why can't they exist independently? and ...