Skip to main content
78 votes

Why are all quarks and leptons of this universe the same?

Fairy Physics It is entirely possible to construct a theory of the universe which states: "All effects are caused by fairies. Each effect has its own fairy, and every fairy is unique. When two ...
Lawnmower Man's user avatar
57 votes

Why the charge of the proton does not transfer to the neutron in the nuclei?

A proton can exchange charge with the neutron via a process called "pion exchange". In this process, the proton with quark content $uud$ sends a positive pion $u\bar{d}$ over to the neutron $...
Xerxes's user avatar
  • 967
49 votes

Why the charge of the proton does not transfer to the neutron in the nuclei?

If I put a red billiard ball and a blue billiard ball in a bag, leave them for a while, and then draw one out, I will find I am holding a red ball or a blue ball. Never a purple ball. At the level of ...
gandalf61's user avatar
  • 53.9k
44 votes
Accepted

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? Some strong pieces of evidence for the quark model of the proton and the neutron, not stated in another answer, are ...
ohwilleke's user avatar
  • 3,903
39 votes
Accepted

Proton: 2 up, 1 down quark, Neutron: 2 down, 1 up, how can Neutron: proton + electron?

A neutron is not "a proton and an electron". A neutron is not composed of a proton and an electron inside of the neutron. In quantum mechanics, particles can appear and disappear or change into other ...
Johnathan Gross's user avatar
35 votes
Accepted

How (or when) do gluons change the color of a quark?

The idea that baryons contain three quarks is a significant oversimplification wrong. It works for some purposes, but in this case it causes way more confusion than it's worth. So you should stop ...
David Z's user avatar
  • 76.5k
33 votes

What is the experimental evidence that the nucleons are made up of three quarks?

Note that the original SU(3) quark model was entirely mathematical (The Eightfold Way) and was a brilliant way to explain the observed spectra of baryons and meson. The whimsically named quarks were ...
JEB's user avatar
  • 33.7k
33 votes
Accepted

Why so much kinetic energy inside a proton?

The simplistic answer is that a proton is very small. The quarks are not free, but are confined to a small region. By the uncertainty principle a small uncertainty in the position of the quarks ...
Dale's user avatar
  • 100k
29 votes
Accepted

Do the quark types differ from each other in ways other than charge and mass?

Yep, quarks of different flavours exhibit important differences in their properties. As we know, quarks participate to all known interactions – but the details of how this happens matter. Let's start ...
Martino's user avatar
  • 977
26 votes
Accepted

Why is the charmed eta meson its own antiparticle, but the neutral kaon is not?

Mesons are not elementary, they are composed of quarks. So take a look at their quark content. The charmed eta meson consists of a charm and an anti-charm quark, denoted $c\overline{c}$. An anti ...
lemon's user avatar
  • 13.2k
22 votes
Accepted

Are there any Baryons that have quark-antiquark combinations?

No, a three-quark baryon can not be be made out of two quarks and one anti-quark (and vice versa) as this would necessarily give the particle color. Each quark carries one of three colors (red, blue, ...
edh's user avatar
  • 346
22 votes

Why are all quarks and leptons of this universe the same?

We know that the spectral lines in the spectrum of a binary star shift one way and then the other and this is correlated with its position in its orbit around its companion. Clearly, the constituents ...
gandalf61's user avatar
  • 53.9k
21 votes

Proton: 2 up, 1 down quark, Neutron: 2 down, 1 up, how can Neutron: proton + electron?

A neutron isn't a proton and an electron. The reaction involved in beta decay is $$n \to p + e^- + \bar{\nu}_e$$ where $\bar{\nu}_e$ is an electron anti-neutrino. But even that doesn't mean a ...
dmckee --- ex-moderator kitten's user avatar
21 votes

Is a 6-quark particle viable?

The deuteron (or $^{2}$H nucleus) is a color-neutral bound state of three $u$ quarks and three $d$ quarks. Because six quarks can combine to make a color-neutral state, this six-quark state is ...
Buzz's user avatar
  • 16.1k
20 votes
Accepted

In which experiment did protons seem to consist of infinite amount of quarks?

Thanks for finding this amazing historical video. He's talking about the deep inelastic scattering electron proton experiment at SLAC. This showed evidence that high energy electrons scattered off ...
RogerJBarlow's user avatar
  • 10.1k
20 votes
Accepted

Why the charge of the proton does not transfer to the neutron in the nuclei?

Good question! First, the motion of charge between macroscopic objects is defined by classical physics, specifically classical electrodynamics or classical Maxwell's equations to be specific. Nature ...
joseph h's user avatar
  • 29.4k
20 votes

Do the quark types differ from each other in ways other than charge and mass?

If the six flavors ($d,u,s,c,b,t$) all had the same mass and charge, they'd all still be distinguishable in the sense that the model still includes observables that (if measured) would detect one ...
Chiral Anomaly's user avatar
19 votes

Are there any Baryons that have quark-antiquark combinations?

Pentaquarks contain three quarks and a quark-antiquark pair, and they are baryons, since baryons are defined as having an odd number of valence quarks.
interoception's user avatar
19 votes

Do protons have a shape?

Lots of experiments to determine the shape of the proton have been performed, beginning in the 1950's. The answer to "what is the shape of a proton" depends on what energy you use to probe ...
niels nielsen's user avatar
19 votes

Why so much kinetic energy inside a proton?

I'm sure the word 'quantum' will begin to show up around here, but the question that bugs me is, would it be possible, theoretically, to take the components of a proton, and very carefully place them ...
naturallyInconsistent's user avatar
18 votes
Accepted

$SU(3)_F$ flavour symmetry and $SU(2)$ isospin symmetry

Both SU(3) flavor and SU(2) isospin are approximate symmetries of the Standard Model at low energies. Consider physics below the proton mass, where we can talk about the pions and kaons that are the ...
Henry Deith's user avatar
  • 1,116
18 votes
Accepted

Can muons decay into quarks?

No, muons can't decay into quarks because quarks are confined; the final product cannot be quarks, but rather composite particles made of quarks, such as mesons and baryons. The lightest mesons are ...
knzhou's user avatar
  • 102k
18 votes
Accepted

Why is the mass of the proton such a precise value?

You say: a zillion gluons and quarks and anti-quarks self annihilating and popping into existence and while this is a very common way to describe the interior of a hadron like a proton it is ...
John Rennie's user avatar
18 votes

Is a 6-quark particle viable?

In principle, a hadron with any number of quarks can be formed provided that the overall color is neutral. However, hadrons with more than three quarks (observed in particle accelerators) are unstable$...
joseph h's user avatar
  • 29.4k
18 votes

Charge distribution of a proton

If quarks had been little point charges with definite positions, then their electric fields would have added up to a non-uniform electric field. But due to quantum mechanics their positions are ...
Anders Sandberg's user avatar
16 votes

Why isn't there a second baryon octet?

These two Figures are excerpt of a page in : A Modern Introduction to Particle Physics, by Fayyazuddin & Riazuddin, 2nd Edition 2000. The first shows the well-known octet of the mixed ...
Frobenius's user avatar
  • 15.8k
16 votes
Accepted

How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content?

The isospin is different. $I=0$ for the $\Lambda^0$ and $I=1$ for the $\Sigma^{0}$. This makes the $\Lambda^0$ an isospin singlet state but the $\Sigma^0$ is part of an isospin triplet. There are ...
ProfRob's user avatar
  • 131k
16 votes
Accepted

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

The charges of the quarks must be simple fractions of the electron charge $e$, because otherwise there would be a breakdown of charge conservation in quantum corrections. The fractions do not need to ...
Buzz's user avatar
  • 16.1k

Only top scored, non community-wiki answers of a minimum length are eligible