What is Hadron: Definition and 68 Discussions

In particle physics, a hadron (listen) (Greek: ἁδρός, hadrós; "stout, thick") is a subatomic composite particle made of two or more quarks held together by the strong force in a similar way as molecules are held together by the electromagnetic force. Most of the mass of ordinary matter comes from two hadrons: the proton and the neutron.
Hadrons are categorized into two families: baryons, made of an odd number of quarks – usually three quarks – and mesons, made of an even number of quarks – usually one quark and one antiquark. Protons and neutrons (which make the majority of the mass of an atom) are examples of baryons; pions are an example of a meson. "Exotic" hadrons, containing more than three valence quarks, have been discovered in recent years. A tetraquark state (an exotic meson), named the Z(4430)−, was discovered in 2007 by the Belle Collaboration and confirmed as a resonance in 2014 by the LHCb collaboration. Two pentaquark states (exotic baryons), named P+c(4380) and P+c(4450), were discovered in 2015 by the LHCb collaboration. There are several more exotic hadron candidates, and other colour-singlet quark combinations that may also exist.
Almost all "free" hadrons and antihadrons (meaning, in isolation and not bound within an atomic nucleus) are believed to be unstable and eventually decay (break down) into other particles. The only known exception relates to free protons, which are possibly stable, or at least, take immense amounts of time to decay (order of 1034+ years). Free neutrons are unstable and decay with a half-life of about 611 seconds. Their respective antiparticles are expected to follow the same pattern, but they are difficult to capture and study, because they immediately annihilate on contact with ordinary matter. "Bound" protons and neutrons, contained within an atomic nucleus, are generally considered stable. Experimentally, hadron physics is studied by colliding protons or nuclei of heavy elements such as lead or gold, and detecting the debris in the produced particle showers. In the natural environment, mesons such as pions are produced by the collisions of cosmic rays with the atmosphere.

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  1. ohwilleke

    I New Naming Rules for Exotic Hadrons at the LHC: LHCb Collaboration Paper (2022)

    The LHCb collaboration at the Large Hadron Collider has developed a new set of rules for naming composite particles bound by the strong force (i.e. hadrons) that are contemplated by existing rules for naming them. This has significant practical relevance to anyone dealing with high energy hadron...
  2. Urs Schreiber

    A Reference for Hadron mass & spin problem?

    I am looking for articles or books that would clearly and succinctly state the open problem of and issues with computing hadron masses and spins in QCD from first principles, preferably in relation to the open problem of confinement and the general open problem of non-perturbative QCD. Any...
  3. A

    A Could the 3D percolation model explain Regge-Trajectories?

    Regge-theory succesfully explains the latest LHC ##pp## elastic scattering experimental results and total cross-sections: https://arxiv.org/pdf/1711.03288 https://arxiv.org/abs/1808.08580 Three different Regge-trajectories are needed: one Reggeon, one (soft) Pomeron and one Odderon. The...
  4. A

    A A Universal picture of hadron interactions?

    As far as I know, the total cross-sections of the following hadron interactions are well described by a single Reggeon trajectory and a single Pomeron (soft Pomeron) trajectory. ##K^-p: (11.93s^{0.0808}+25.33s^{-0.4525})mb## ##K^+p:(11.93s^{0.0808}+7.58s^{-0.4525})mb## ##\bar...
  5. S

    I Specifically, why is the neutron heavier than the proton?

    Proton is made of 2 up, 1 down quarks Neutron is made of 2 down, 1 up quarks The up and down quark have different masses, which account for some of the mass difference. I've also read that hadron masses depend upon the interactions/dynamics inside the particle, not just the quarks contained...
  6. ohwilleke

    I Excited hadrons v. fundamental particles

    Mesons and baryons have both a ground state and excited states involving the same valence quarks but a higher mass (which can in principle be calculated from QCD). Fundamental fermions and bosons, however, do not appear to display this behavior. They have a ground state, and while there are...
  7. A

    B How fast are the the protons in the large Hadron collider?

    Hi, I was asking how fast is the fastest Hadron ever moved in the large Hadron collider.And most importantly how do they calculate it? Do the calculate it mathematically or with a detector?
  8. P

    B Quark/Gluon Ensemble In Hadron

    I know the PF rules regarding using only peer reviewed texts, but in this case, it's the only source I have access to and I'm not trying to promote the content in any way, really I'm just trying to understand if it is actually saying what it seems to be. https://arxiv.org/pdf/1303.3752...
  9. D

    Stargazing Programable telescope that will point to any spot on Earth?

    Is there a programmable telescope that will point to any spot on Earth from my location that I could simply plug in the latitude and longitude and it would point at the location anywhere on Earth. For instance, if I wanted it to point at the LHC (Large Hadron Collider), could I just plug in the...
  10. B

    A R value in electron positron annihilation

    In the calculation of R=σ(e+e-→hadrons)/σ(e+e-→μ+μ-) from BaBar experimental data at a center of mass energy of √s≈10 GeV i obtain R=5. Theoretically I should get a value of R=10/3. I know it has something to do with the resonances of ϒ mesons shown in the plot attached, but I don't know how to...
  11. P

    B Bose–Einstein condensate and Hadron Collider

    Just out of curiosity I was wondering what would happen if a Bose-Einstein condensate were placed in a Hadron Collider. Is it even possible?
  12. 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?
  13. R

    I What is the weak isospin of hadrons?

    What are the weak isospins (T3 values) of various hadrons, including the proton, neutron, mesons, hyperons and other hadrons? How is the weak isospin calculated for any hadron? Published sources provide T3 only for fundamental fermions, that is, quarks and leptons. In the fundamental bosonic...
  14. Beanyboy

    B Is the Large Hadron Collider large?

    Or, is that that the hadrons are large? Or, are they both large? What exactly is the adjective "large" qualifying please? I do know that the tunnel is very large indeed, and that this is the most sophisticated machine ever built.
  15. K

    I Has Large Hadron Collider shown Higgs conformal invariance

    the higgs naturalness problems has several solutions 1- natural susy 2- technicolor 3- extra dimensions 4- conformal invariance Large Hadron Collider has to date strongly disfavored susy, technicolor, extra dimensions. it is highly unlikely susy is the answer to the higgs hierarchy problem...
  16. danihel

    Do hadron particles have half-life?

    Hi, i heard that as the universe will expand and the energy will grow sparse, in the end the matter itself will turn into radiation that will loose energy. So i wanted to ask, can a proton decay? and is it the same phenomenon as radioactive decay? Does it mean that even hydrogen (with no...
  17. K

    Is a Small Space Hadron Collider More Efficient than a Large One?

    It's to my understanding that the Large Hadron Collider is so 'large' due to the fact E=MC^2 and that when the accelerated particles approach the speed of light their mass increases logarithmic to a near infinite mass, meaning the magnetic force applied to the particle, to stop it from touching...
  18. terra

    Non-leptonic hadron decays: preferred paths?

    My background of some introductory courses in particle physics has left me with severe shortcomings. Say we start from a hadron, which decays purely to other hadrons. My question is this: through which interaction does the process take place? Is there a preferred interaction, and why/why not...
  19. U

    Production of Z boson - Cross Section

    Homework Statement Calculate the ratio ##R = \frac{\sigma_{had}}{\sigma_{\mu+\mu-}}## for energy around ##10~GeV##. At sufficiently high energies, the ##e^+e^- \rightarrow \mu^+ \mu^-## reaction can proceed via the ##Z^0## boson. Assuming vertex factors for EM and weak interaction are the same...
  20. U

    Special H boson with very high cross section?

    Homework Statement (a) Explain the results. (b) Why is the cross section much higher? Suggest the dominant decay product pair.[/B] Homework EquationsThe Attempt at a Solution [/B] Part(a) For a centre of mass energy of ##170GeV##, you produce pairs of oppositely charged ##W^{\pm},W^{\mp}##...
  21. U

    Psi Meson Decay Modes: Spin, Parity, Quark Content & More

    Homework Statement (a) Explain spin and parity of mesons (b) State their quark content (c) Draw a feynman diagram of J/psi decay (d) Why doesn't ##\chi## undergo leptonic decay? (e) What is the minimum centre of mass? [/B] Homework EquationsThe Attempt at a Solution Part(a)[/B] Spin is...
  22. Math Amateur

    MHB What Will the Restarted Large Hadron Collider Uncover About Dark Matter?

    Large Hadron Collider is restarting ... wonder what will be discovered ... particles somehow related to dark matter ... and other wonders ... Cern restarts Large Hadron Collider with mission to make scientific history | Science | The Guardian Peter
  23. greasehoot

    Formula for the vibration rate of an atom?

    Just a general inquiry, and not for any personal gain and or theory, I would like to know if anyone has developed a formula for measuring the vibrational rate of an atom.
  24. K

    Entangled Particles and the Hadron Collider?

    If one was to entangle two particles and either send the two particles at each other, or send one of the entangled particles and observe the other; what do you think might happen? If there are any problems with getting an entangled particle into the Hadron Collider, please say so.
  25. T

    What would happen if I was standing in the LHC

    What would happen if I was standing in the LHC and I was hit by a (one) proton traveling at 99.999991% the speed of light. Would the collision burn a hole in me? or would it simply be going so fast that it passes through me without interacting with the particles in my body?
  26. wolfspirit

    Hadron interaction via strong yet k mesons decay through weak

    Hi, I have been getting a little confused; the textbook (and from what i can see on-line) are saying that Hadrons only interact through the strong interaction (along with the electromagnetic force if charged Q) and yet K Mesons decay through the weak interaction. If my understanding is correct...
  27. G

    How are the masses of hadrons calculated from their constituent quarks?

    How is the mass of hadrons calculated from constituent quarks? It seems classically it should come from three parts: (p2+m2)1/2 for each constituent quark with rest mass m, plus interactions between the quarks, which would be electromagnetic Coloumb 1/R potential between any two of the three...
  28. J

    How to determine the force in hadron decays

    I was wondering if someone could explain to me how you determine how a Baryon/Meson decays, meaning Strong decay, Weak decay, and Electromagnetic decay. Or if you could simply link me to a chart with a list of all of the forces they use to decay (if such a thing exists, I can't find one) it...
  29. S

    Build a Model Hadron Collider at Home!

    Hi guys, I have the idea of putting together a model collider that fires two smashable objects (eggs or whatever) at each other and show a high speed camera footage of the objects hitting each other - this is all as an analogy of what the hadron collider does at CERN. Any ideas what I...
  30. H

    Why We Study Hadron Physics: Exploring the Decay Constant of Mesons

    Dear all; why we study hadron physics? For instance different people calculates the decay constant of mesons using different methods and they get approximately the same result, the difference is too small. So why not people they apply the same mathematical method?
  31. J

    LHC Sim: Hydrogen Atoms & Quark Charges

    I was on the LHC simulator and the collisions of the Hydrogen atoms were confusing. Why were some uniform in direction while some spinning erratically in a cork screw pattern? Does that behavior have anything to do with the positive or negative charges of the Quarks in the nucleus?
  32. howabout1337

    Do the Large Hadron Collider take earth's rotational speed?

    so according to wiki: protons have a Lorentz factor of about 7,500 and move at about 0.999999991 c, or about 3 metres per second slower than the speed of light (c) If we consider speed of Earth's rotation or speed at which two galaxies approach each other (collision or otherwise)?
  33. S

    Exploring the Inertial and Rest Mass of Quarks and Gluons in Hadrons

    Quarks are imprisoned in hadrons, and have large binding and kinetic energies at all times. Ditto about gluons. How can inertial mass of quarks inside hadrons be measured? Also, how is it proven that gluons are massless? What effects would happen if gluons had rest mass, as much as up to a...
  34. Q

    When were hadron jets first discovered?

    Hey guys! I have a quick question! When were hadron jets first dicvovered? I would appreciate a year and month if possible:smile:
  35. M

    Reason for dipole and quadrupole magnets in the Large Hadron Collider

    According to Wikipedia, the source of all knowledge, the LHC contains some 1,232 dipole magnets with an additional 392 quadrupole magnets. What is the difference in function between the two types of magnets? How might the effects of magnetic field gradients contribute to the differences...
  36. J

    Understanding IR Divergences in Hadron Colliders

    Hi @ all, I have a question about IR divergences at hadron colliders. I can see that there are also IR divergences in loop diagrams such as the vertex correction and so on... I also see the IR ones in the real gluon/quark/ or photon emission... so that for example the gluon is soft or...
  37. E

    Hadron Mass, MC^2 and Gravity

    I cam across this statement in Wikipedia: Note that the mass of a hadron has very little to do with the mass of its valence quarks; rather, due to mass–energy equivalence, most of the mass comes from the large amount of energy associated with the strong interaction. I find it somewhat...
  38. D

    The Hadron collider shooting particles at JUST under speed of light.

    Hi just a quick question, why do they choose to collide the ions at just under the speed of light? what would happen if they were shot at the speed of light or higher?
  39. B

    Hadron Cross Section Calculation

    Hi all, I'm trying to understand the solution to a problem from a textbook. We're asked to find the proportionality constant for $$\frac{d\sigma_{\rm elastic}}{dq^2}\propto e^{bt},$$ where q is the momentum transfer in a scattering process, defined in elastic scattering as...
  40. S

    Large Hadron Collider - can it re-create the early universe?

    One of the aims of the Large Hadron Collider is that it may be able to re-create conditions in the early universe and therefore produce the quark-gluon plasma that appeared microseconds after the universe's birth. However a fundamental difference between the universe now (in which the...
  41. P

    Who discovered the Hadron and when?What properties does the Hardron

    Who discovered the Hadron and when? What properties does the Hardron have? What are all the interesting facts about the hadron?
  42. L

    Hadron collider substance used

    Q.) what substance is used for the hadron collider, the metal? I presume a metal compound of some sort but was wondering which and would it have to withstand high temperatures or are the electromagnets used kept at low temperatures due to better effieciency?
  43. E

    Hadron Resonance Gas: Exploring QCD Data & Thermodynamic Model

    Recently I saw a talk stating that the hadron resonance gas model, which is basically all the known hadrons put together as ideal gases, describes lattice QCD "data" really well. Like in this paper: http://arxiv.org/abs/hep-ph/0303108 In this paper Fig. 1 is what I am looking at. I tried that...
  44. Z

    Large Hadron Collider - Few Questions

    Can anyone explain a bit how does the LHC uses magnetic filed to accelerate protons? And why does it use protons for the collision? Couldn't they have used electrons?
  45. B

    Explore the Large Hadron Collider (LHC)

    Large Hadron Collider! Hello again...I'm back! Now I got another amazing physics investigation :D This assignment is due next week and it's about the Large Hadron Collider (LHC) The task requires me to write the research of its development and application, purpose, use of fields in and the...
  46. Loren Booda

    Fitzgerald contraction for a proton in the Large Hadron Collider

    By what factor would the radius parallel to the direction of travel contract for a 7 TeV proton, relative to an antiparallel 7 TeV proton, in the Large Hadron Collider?
  47. maverick280857

    Understanding Hadron Structure through Electron-Positron Collisions

    Hi, Halzen and Martin, on page 18 of their book, describe the resolution of hadron structure using virtual photons obtained by annihilating e+ and e- beams. In Figure 1.11(b), isn't the positron arrow shown wrongly? It seems to be moving forward in time. (Or maybe I'm just being picky...
  48. M

    The Large Hadron Collider - Where is the particle?

    Ok, apologies if my understanding is limited or even wrong but I know I'll learn something from your replies even if my question turns out to be idiotic! Relativity gives us length contraction as we approach the speed of light but quantum mechanics gives us uncertainty as to a particles...
  49. P

    How do GM tubes detect charged particles in a hadron collider?

    1) Why do the electrodes in a linear accelerator get progressively longer? 2) What is a synchrotron? what is it used for? 3) How does a Geiger-Muller (GM) tube work? 4) How are particles detected in a hadron collider?
  50. B

    Large Hadron Collider questions

    I watched some interesting videos on the Large Hadron Collider (LHC) and it raised a whole ton of questions. If my questions do not make any sense, perhaps the video itself, though clever and catchy, is not credible. ( http://technology.todaysbigthing.com/2008/09/11 +...