What is Quarks: Definition and 255 Discussions

A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly observable matter is composed of up quarks, down quarks and electrons. Owing to a phenomenon known as color confinement, quarks are never found in isolation; they can be found only within hadrons, which include baryons (such as protons and neutrons) and mesons, or in quark–gluon plasmas. For this reason, much of what is known about quarks has been drawn from observations of hadrons.
Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. They are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge.
There are six types, known as flavors, of quarks: up, down, charm, strange, top, and bottom. Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators). For every quark flavor there is a corresponding type of antiparticle, known as an antiquark, that differs from the quark only in that some of its properties (such as the electric charge) have equal magnitude but opposite sign.
The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until deep inelastic scattering experiments at the Stanford Linear Accelerator Center in 1968. Accelerator experiments have provided evidence for all six flavors. The top quark, first observed at Fermilab in 1995, was the last to be discovered.

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  1. M

    B The Force of protons and quarks?

    How much force will it required to pull a quark out of a proton, and how much for to pull a proton out of a atom ?
  2. ValeForce46

    B Kinetic energy of quarks in a baryon

    If we say that a proton has a kinetic energy of ##50## GeV, can we say that each of the three quarks that compose it have roughly a mean energy of ##\approx\frac{50}{3}=17## GeV? If not, what can we say about the energy of each individual quark inside a baryon with a known energy?
  3. Quantummanphoton

    Exploring the Possibility of Quarks as Transistors

    Instead of electron transistors why not go smaller particles like quarks?
  4. T

    Mass: Uniting Quarks & Antimatter in Unexpected Ways

    Mass behaves opposite that of other quantum numbers when combining matter (quarks) and antimatter. Why?
  5. T

    Can Left Handed Up Quarks Transform Into Right Handed Ones?

    Isospin must be transformable if it is the case. In which case there must be additional Bosons for doing the transformation.
  6. H

    B How hard have they banged on quarks, electrons, etc.?

    I think there are so far as we can tell particles of mass that are made up of quarks and leptons (electrons and what not). So far as we know those the fundamental particles of matter. Question - how hard have we banged on quarks/leptons to see if we can blow those up into smaller units? I...
  7. Cody Livengood

    B How do we know gluons exist?

    I understand how the existence of quarks is inferred from the three particle-emitting cones or jets and by the quarks’ ability to deflect particles passing through the composite particle, but I don’t see how the existence of gluons is conclusively demonstrated by this rather than just being an...
  8. V

    B How does exchange of elementary particles result in a force?

    Homework Statement:: I came across the following in an online article. I am unable to understand how these elementary particles cause a force to exist. "Each of the four forces results from the exchange of force-carrier particles.". Above statement is taken from...
  9. A

    A No CP-Violation for coinciding Quark-Masses

    Hello everyone, I know that if two of the quarks (e.g. strange & bottom) had coinciding masses, there would be no CP-violation in the standard model. Apparently the reason lies in the parameters of the CKM-matrix, but I don't understand how to show that. Can someone explain?
  10. bbbl67

    I Would higher-mass quarks result in smaller baryons?

    Would baryons not made with standard Up or Down quarks exhibit smaller radii than neutrons and protons? I'm thinking like for example how muons have much smaller orbitals than electrons, on the lepton side of things.
  11. Sphere

    B How did quarks appear in the Universe?

    Hello, from what I understood at the very beginning of the universe, the universe was too dense and too hot to allow matter (atoms) to exist, so at the very beginning, the universe was a kind of soup of quarks (components of protons and neutrons). What I was wondering is how quarks appeared in...
  12. ohwilleke

    A What New Experiments, If Any, Would Help Determine Light Quark Masses?

    The experimentally measured properties of protons and neutrons are known with exquisite detail. Our data is not quite as extremely precise, but still very good more other baryons and mesons with light quarks (u, d, and s) as valence quarks, such as pions and kaons. Yet, on a percentage basis...
  13. LCSphysicist

    I Current theory of composite quarks and leptons

    "M. Shupe [Phys. Lett. 86B, 87 (1979)] has proposed that all quarks and leptons are composed of two even more elementary constituents:" (Griffiths) I am redoing the book of elementary particles from Griffths, and this exercise has showed really interesting to me. How is the currently status of...
  14. D

    B Quarks, electrons, neutrinos, and photons?

    Can someone please explain the four classes of fundamental particles? (Just the basics) I came here because I never learned any chem or physics in school so please explain like I’m five :)
  15. N

    B Are quarks fundamental elements of matter?

    I would like to ask scientists or anybody: what do you think about qwarks, do you consider them to be the littiest parts of matter or that matter is cyclically or infinitaly smalling, like numbers, or that there are some smaller parts, which have not been observed, but they have an end in their...
  16. elcaro

    B Could atoms be formed from other quarks than up and down?

    Is it possible - perhaps in a different universe with different physical constant and vacuum energy - that atoms can be formed from strange/charm or top/bottom quarks?
  17. Sheldon73

    B What is made up of all the rest quarks?

    The proton and neutron are composed of up and down quarks. What is made up of all the rest quarks?
  18. W

    B Electrons, quarks and gluons made from something or nothing?

    Most articles said electrons, quarks and gluons are indivisible thus have no compositions unlike the other particles. So, does that means electrons, quarks and gluons are composed of nothing and these elementary particles are indeed 100% void?
  19. N

    Prerequisites for studying Quarks and Leptons (Halzen and Martin)

    I study physics on my own and just ended up Griffiths' book on Quantum Mechanics. Is this level of QM enough to be able to study Halzen and Martin's Quarks and Leptons book on particle physics? I planned on studying it while studying Sakurai QM, but I just wanted to be sure that I could at least...
  20. K

    I The spin of quarks in an H dibaryon

    I have some difficulties interpreting an exercise. It states that the dibaryon H is made of uuddss, with total spin zero, and relative angular momentum 0 as well. It then proceeds to use that the spin of every pair of particles uu, dd, and ss is equal to 1. Why is that the case? It seems obvious...
  21. bbbl67

    I Strange quarks, Strange stars and Strangelets?

    So various articles and videos suggest that if a piece of strange matter, or a strangelet, were to touch the Earth, the entire Earth would eventually get converted into strange matter too. Now, from what I've read strange quarks have a half-life of ##10^{-10}## s, so I can't see how it would...
  22. M

    I Higgs decay to 2 top quarks

    Hello! I haven't really seen a feynman diagram with a higgs boson decaying to a top-anti top quark pair. The mass of a top pair is much higher than the Higgs mass on shell, but is there any reason why we can't have a Higgs boson (very) off-shell decay to 2 top quarks. The probability of that...
  23. A

    I Have we observed asymptotically free quarks?

    At high energies, quarks behave like single particles, due to the asymptotic freedom in QCD. Have we observed these free quarks yet in experiment? Does the freedom energy match the theoretical models?
  24. bilzebor

    A Difference between generations of quarks

    hello, in the model of quarks, each of them is described by a flavor, but the quantum number for the first generation of quarks is the same (the isospin) for the up (1/2) and down (-1/2) quark. For the other generation though it is a distinct number (s,charm,...) for each quark. From what I...
  25. Attu

    B Quarks -- real world problem

    quantum field physics gives us real good understanding different kinds of forces. i got interested in this topic when i was reading a textbook . and i found interesting how for quantum chromodynamics there are eight types of quarks and all have different effects. but in the book it was not...
  26. N

    I Color state of quarks in quark-gluon plasma

    Hi, I have been taught that quarks don't exist individually on their own, as they has with be with at least another antiquark to form a colorless state. But in the quark-gluon plasma, do we have individual quarks in a color state or do they still, somehow, are in a color-neutral state? Thanks!
  27. MacGyver Megh

    B The electromagnetic force of quarks

    If an up quark has 2/3 of positive charge and down quark has 1/3 of negative charge then why don't they add together by their electromagnetic force?
  28. Anthony Beckwith

    B Quarks and Antiquarks in a baryon

    If Quarks and Antiquarks are bound together and don't appear individually why does baryon have 3 quarks but no antiquarks? Again apologies if this is obvious and or novice. Thanks Anthony
  29. K

    I Understanding the W Decay Branching Ratio to Quarks & Gluons

    Hello! In Modern Particle Physics by Mark Thomson, in the Electroweak Unification chapter, pg. 412 he talks about the branching ration of the W decay to quarks. And for this he includes both the ##W\to q \bar{q'}## and ##W\to q \bar{q'}g## i.e. the state with a gluon and 2 quarks in the final...
  30. H

    How to present the charges of quarks with the following Nc?

    I have already known the cross sections can be presented like this. σ(e+e- -> hadrons)∝ Σ eq^2 & σ(e+e- -> μ+μ- ) ∝ e^2, where eq is the charge of a certain quark(u, d, s, c or b) But I don't know the relationship between Nc and eq. (This is my first time to post a thread. I don't know how to...
  31. J

    I Why are all quarks considered fundamental?

    Summary: If 5 of the quarks can eventually decay into the up (plus other stuff), why are they still considered fundamental? I can't decide if I'm just misinterpreting the word fundamental in this particular usage or if there is something about the non-up quarks that makes them fundamental even...
  32. Zeynel

    I What is a realistic image of quarks?

    In this CERN video quarks are represented as spheres. Is this how quarks look like. I thought they were fluctuations in the quantum field.
  33. Q

    B Neutral pion quark composition help

    Hi guys, Merry Christmas to you all! I wanted to know whether a neutral pion can be made up of a strange quark and an anti-strange quark. I know that the kaon is the only strange meson and all variations contain an s quark but wouldn't the strangeness be zero in an s quark/anti-s quark pair as...
  34. B

    A Spin direction of quarks in a baryon

    If all three quarks in a baryon have the same flavor, they all spin the same direction, causing the baryon to have 3/2 spin. In a proton, do both up-quarks spin in the same direction (with the down-quark spinning opposite)? Or can the two up-quarks spin in opposite directions?
  35. DarMM

    A How can quarks exist if they are confined?

    Moderator's note: this thread is a spin-off from https://www.physicsforums.com/threads/self-interference-in-double-slit-experiments.952744/ According to nonperturbative QCD, quarks and gluons don't exist and in nonperturbative QED with two spinors (e.g. proton and electron) hydrogen isn't...
  36. HEPlover

    A Are valence quarks real physical entities?

    Im carefully studying Deep Inelastic Scattering and I have the doubt if valence quarks are real physical entities or if they are just a way we can think hadrons are built. I understand that inside hadron we have the Parton Distribution Functions that say that there are an infinite number of...
  37. T

    I Higgs Boson decay to two Quarks Detected

    https://phys.org/news/2018-08-long-sought-higgs-boson.html
  38. L

    I Are dark matter quarks displaced by visible matter?

    Are strongly interacting dark matter quarks displaced by visible matter? Chiral Gravitational Waves and Baryon Superfluid Dark Matter We develop a unified model of darkgenesis and baryogenesis involving strongly interacting dark quarks
  39. R

    A Electron charge vs quark charge

    I have been trying to understand some of the basic differences in the fundamental nature of leptons and quarks. One article on this issue compares leptons and quarks as "oranges vs apples" to which I basically agree except for one aspect. How can the charges of the quarks be 1/3 or 2/3 the...
  40. F

    I Exploring the Three Generations of Quarks and Their Properties

    I understand there are three generations of quarks, which have the same charge but different mass. My question is, in a single generation how many different kinds of quarks are there. For example, in the first generation there are the up quark and down quark, each of which has an antiquark. So...
  41. H

    I Is the strong nuclear force stronger than the weak force?

    I've heard that the weak nuclear force is stronger than the electromagnetic force at distances of 10^-18 m. I've also heard that the strong force becomes repulsive at a distance of 0.7 fm. So if two quarks got to a distance of <<10^-18 m which force would win, the strong force or the weak force?
  42. bbbl67

    I Is the Melting Quarks Experiment a Scam?

    Okay, I've been seeing the following story circulating around various websites. I get the feeling that it's a scam, but I don't want to prejudge it. So I thought I'd ask the various experts about what they think of it...
  43. M

    A Attractive strong force, isospin and hypercharges

    In the electromagnetic interaction, opposite electric charges q attract each other. In the strong nuclear force, the proton p(uud) is attracted to p(uud) and the neutron n(udd), and n(udd) is attracted to p(uud) and n(udd). Both neutrons and protons have a hypercharge Y=+1, and 3rd...
  44. R

    I W Boson and different generations of quarks

    Can a W Boson convert an up quark into a down quark of the same generation? Where can I find a resource to understand what all the possibilities are for an up quark converting into other quarks of same or other generations?
  45. mpolo

    B Energy of Up & Down Quarks in Joules: What Are They?

    I am using a program that requires the energy of the up quark and down quark be given in Joules. I tried to find these values on the internet but could not find these values. Can someone please tell me what is the energy of the Up and Down Quark in Joules?
  46. K

    B Are there Hadrons with more than three quarks?

    As far as I know there are Mesons (quark-Antiquark pair) and Baryons (three quarks). But are there Hadrons which contain more than 3 Quarks?
  47. mpolo

    B How did we measure the mass of Quarks?

    I have searched the Internet and I have not found a simple layman's explanation other than this. We observe their decay products of quarks and that is what the mass is reconstructed from. Is this correct? If so I would like to have that confirmed. I am just looking for a simple direct...
  48. P

    I Can all the Quarks be found in the Sun?

    so, I was told that only Up and Down are stable Quarks in the nucleus, and the others are only explained by observations in particular decay.
  49. zinq

    B Does every elementary particle eventually decay into quarks?

    Everything in the universe that has a beginning seems to also have an end. Stars, galaxies, molecules, atoms. But what about elementary particles? In case of heat death would it become a uniform quark soup?
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