Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [quarks]

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

0
votes
2answers
23 views

What happens if matter particle and antimatter particle both carry no charge were to collide elastically?

I read that particle carrying charge is able to interact with photon so that when electron and positron collides they may be converted into pure photons, then what about neutron-antineutron collision? ...
0
votes
1answer
34 views

How can pure leptonic interactions be mediated by the weak force?

$\mu^+ \rightarrow e^+ + \nu_e + \bar \nu_\mu$ Consider the above decay, it is given in my lecture notes as a weak force interaction. I thought the weak force was only involved when quarks change ...
0
votes
1answer
46 views

What are direct experimental evidences that quarks exist? [duplicate]

Now we have very established model of quarks explaining fundamental strong interaction. What are experimental proofs for existence of quarks and what is the name of physicist which made them?
3
votes
1answer
80 views

Most of the momentum of a proton is carried by the quarks

I saw this in wiki https://en.wikipedia.org/wiki/Antiproton#Modern_experiments_and_applications "the valence quarks in the proton, and the valence antiquarks in the antiproton, tend to carry the ...
1
vote
1answer
42 views

Why do we have 3 quantum colours?

I understand the need to invoke colour as another quantum state to explain the observation of uuu ddd and sss baryons. I just wanted to know if there was some other property which explains why we only ...
1
vote
1answer
34 views

How is the charge conserved at the up to anti-down vertex?

I can see how the charge is conserved in the overall diagram but I can not understand how it is conserved at the up to anti-down vertex.
2
votes
1answer
30 views

Is the (range of the) strong force the same for nucleons and quarks?

In high school, I learnt that the strong force held the nucleus together. It had a very short range and was repulsive at small separation distances to prevent the nucleons from collapsing. Now I am ...
5
votes
2answers
810 views

Can muons decay into quarks?

Muon decays are almost always written as $$\mu^- \rightarrow e^-+ \bar\nu_e +\nu_\mu.$$ The reason given on wikipedia is that one of the product neutrinos of muon decay must be a muon-type neutrino ...
4
votes
1answer
96 views

Why is the neutron magnetic moment negative?

I understand that the magnetic moment is due to the quarks, but specifically why is it negative? Is it due to the two down quarks or something?
10
votes
2answers
1k views

Besides the up and down quark, what other quarks are present in daily matter around us?

Protons and neutrons, which are found in everyday matter around us, compose of up and down quarks. Are the other two generations of quarks, i.e. $c,s,t,b$ quarks found in everyday matter around us? I ...
1
vote
0answers
18 views

Mass splitting for leptons and down quarks in $SU(5)$ model?

In the minimal $SU(5)$ GUT model, the masses of the leptons and the corresponding down-type quarks must be equal. i.e. $m_e=m_d$, $m_\mu=m_s$, $m_\tau=m_b$. Whereas this is approximately correct for ...
3
votes
1answer
65 views

What Does Up-Down Asymmetry Mean?

There is strong experimental evidence (reported on in the linked paper), from more than one high energy physics experiment, that up-down asymmetry is present in the decays of certain charmed baryons. ...
0
votes
2answers
61 views

Can someone explain the $ttH$ Coupling?

IS the $ttH$ an actual particle? If so, how can it form? I though the life of the top quark was way to short to form a particle. If it is not a particle, what is meant by coupling.
0
votes
1answer
43 views

Does an antiparticle leave a different (from the normal particle) mark in a bubble chamber experiment

Experimentalists usually have experiments where they scatter particles superheated transparent liquid, thus checking for the particle's traces. These particles can be for example quarks, and ...
2
votes
0answers
52 views

Strange Quark Matter

I am watching a video on neutron stars. The video is discussing the collision of 2 neutron (quark) stars and the ejection of strangelets. That if one of these strangelets comes into contact with ...
0
votes
0answers
34 views

How many quark flavor quantum numbers are really needed?

Several authors I've consulted recently use six separate flavor quantum numbers for the six observed flavors of quarks when constructing their QCD Lagrangians That seems excessive when three "family" ...
0
votes
0answers
13 views

Measurement of spin asymmetries in semi-inclusive deeply inelastic scattering (SIDIS)

I have been reading several papers regarding the spin asymmetries for SIDIS. One thing I was trying to understand is the method of extraction of symmetries. When I read the single spin asymmetries, ...
1
vote
1answer
51 views

How can weak interactions not conserve strangeness if the SM always conserves energy?

I have read these questions: Weak Interaction and Strangeness transformation Weak decay iff or if strangeness changes? Understanding type of force interaction in particle decays The decay of the ...
2
votes
1answer
40 views

How would the structure function of protons be different if quarks had spin 0?

I saw this question in a practice exam. I know that the structure functions are not linearly independent but that $F_2(x)=2xF_1(x)$ when the energy is in the order of GeV. The question asks what ...
1
vote
0answers
44 views

Computing the decay width for Top quark decaying to bottom quark and W boson

I have been trying to calculate the decay width for the $t \rightarrow bW^+$ decay. After having done this numerous times, I can not figure out how the result $$\Gamma = \frac{g^2m_t^3}{64\pi m_W^2}\...
6
votes
2answers
98 views

Why is the up quark is lighter than the down quark, while top is heavier than bottom?

Up, charm and top seem to be similar in terms of electric charge (+2/3e) while down, strange and bottom have also same charge (-1/3e). In the second and third family, positively charged quark has ...
0
votes
3answers
74 views

Can a quark quantum tunnel outside a nucleus?

I read that a particle wavefunction can extend over a thin barrier and there is a probability of finding it over the barrier even though it doesn't have the necessary energy, what about quark?
1
vote
1answer
47 views

How and why is the pentaquark stable if it consists of 4 quarks and an antiquark?

If matter and antimatter annihilate each other, why is the pentaquark stable since quarks are matter and the antiquark is antimatter?
1
vote
0answers
38 views

How does hexagonal boundary arise in $SU(3)$ representation?

I am having trouble trying to understand the hexagonal boundary in $t_3$ and $y$ representation of $SU (3)$. I tried to work it out like we did in $SU \left( 2 \right)$ but got not luck. Could someone ...
0
votes
0answers
36 views

Why are mesons only made of a quark-antiquark pair? [duplicate]

Why can't we have a meson made of two quarks, why does there have to be the antiquark too?
4
votes
1answer
99 views

How do we know that gluons have no electric charge?

Since the W boson carries electric charge and there is no a priori reason that massless electrically charged bosons cannot exist, I'm wondering if the lack of gluon electric charge has been confirmed ...
0
votes
3answers
92 views

Why is the proton (uud) lighter than the $Δ^0$ (uud) baryon?

Neutron has quark composition udd with spin $\frac 12$. $\Delta^0$ baryon has quark composition udd with spin $3 \over 2$. On Wikipedia it says that $\Delta$ baryons have mass of approximately $1232 ...
3
votes
1answer
64 views

How can matter and anti-matter coexist in a meson?

Whilst learning about the nature of subatomic particles, I came along a pion zero meson. What really stumbled me was that the quark configuration of the particles was up and anti-up or down and anti-...
0
votes
1answer
57 views

If a particle decay has quark annihilation will it always emit a photon?

From what I can gather the decay $\pi^0 \rightarrow \gamma \gamma $ emits two photons because $\pi^0 $ has quark content $(u\bar u-d\bar d)/\sqrt{2} $, and the $u$ annihilates with $\bar u$, and $d$ ...
3
votes
3answers
82 views

How do leptons differ from one another?

All the leptons that I have come across have their native (matter) charges of -1 relative to the charge of an electron. Since they are all fundamental and are not made up of quarks, you can't ...
0
votes
0answers
17 views

If the combinations, in the context of particles which have identical interactions, are not orthogonal to each other?

I read from here If there are two or more particles which have identical interactions, then they may be interchanged without affecting the physics. Any (complex) linear combination of these two ...
0
votes
0answers
57 views

Quark flow diagram for $\rho^0 \rightarrow \pi^0+\gamma$

So $\pi^0=\frac{1}{\sqrt{2}}(u\bar{u}-d\bar{d})$ and $\rho^0=\frac{1}{\sqrt{2}}(u\bar{u}-d\bar{d})$ except with a higher angular momentum, this angular momentum is taken by the photon. How do I ...
0
votes
3answers
118 views

Difference between $W^-$ and $\pi^-$

Maybe it's a very naif question, but what is the difference between a $W^-$ and a $\pi^-$? I mean they both change a $d$ into a $u$ right? $d \rightarrow u W^- \quad \text{and} \quad d \rightarrow ...
0
votes
3answers
168 views

Why do quarks and gluons have colour?

I asked a question here a few days ago and got some fantastic answers so I'm going to continue. Let me preface this by saying I know quarks do not actually have 'colour', but colour is some sort of ...
-1
votes
2answers
42 views

Naive question about lepton/quark energy states

I understand there are 3 energy states for quarks and leptons (electron, muon, tauon... Up, charm, top etc.) And we have 3 forces (not including gravity, em, strong and weak). This naively seems ...
3
votes
2answers
85 views

How are composite hadron fields related to elementary quark fields?

(This question is related to: A pedagogical exposition of the hadron physics?) I'm a mathematician who has been trying to learn quantum field theory for a while. I've gone through large parts of ...
3
votes
2answers
130 views

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 ...
0
votes
1answer
27 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 ...
2
votes
1answer
55 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 ...
-1
votes
1answer
30 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.
2
votes
0answers
31 views

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 ...
1
vote
1answer
44 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 ...
5
votes
1answer
129 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 ...
2
votes
2answers
160 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)...
1
vote
1answer
71 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?
1
vote
1answer
111 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 ...
1
vote
1answer
81 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 ...
1
vote
1answer
54 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?
1
vote
1answer
187 views

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 ${\...
5
votes
1answer
148 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 ...