Baryon Definition and 91 Threads

In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classified as fermions because they have half-integer spin.
The name "baryon", introduced by Abraham Pais, comes from the Greek word for "heavy" (βαρύς, barýs), because, at the time of their naming, most known elementary particles had lower masses than the baryons. Each baryon has a corresponding antiparticle (antibaryon) where their corresponding antiquarks replace quarks. For example, a proton is made of two up quarks and one down quark; and its corresponding antiparticle, the antiproton, is made of two up antiquarks and one down antiquark.
Because they are composed of quarks, baryons participate in the strong interaction, which is mediated by particles known as gluons. The most familiar baryons are protons and neutrons, both of which contain three quarks, and for this reason they are sometimes called triquarks. These particles make up most of the mass of the visible matter in the universe and compose the nucleus of every atom. (Electrons, the other major component of the atom, are members of a different family of particles called leptons; leptons do not interact via the strong force.) Exotic baryons containing five quarks, called pentaquarks, have also been discovered and studied.
A census of the Universe's baryons indicates that 10% of them could be found inside galaxies, 50 to 60% in the circumgalactic medium, and the remaining 30 to 40% could be located in the warm–hot intergalactic medium (WHIM).

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  1. 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?
  2. T

    What is Baryon Decuplet in Physics?

    Hello sir What is baryton decuplet
  3. Safinaz

    A How to find the value of the baryon asymmetry in this paper

    I'm trying to understand from this paper https://pdg.lbl.gov/2020/reviews/rpp2020-rev-bbang-nucleosynthesis.pdf What is the value of the baryon to photon ratio ##\eta=n_b/n_\gamma## as named in figure 24.1, but I can't get from the figure or the paper how ##\eta## is of order ##10^{-10}## Any...
  4. joneall

    A Why does D(1,1) representation of SU(3) give baryon octet?

    The question may be ambiguous but it's really simple. One says that the baryon octet is the D(1,1) representation of SU(3), but then uses the same one for mesons. D(1,1) means one quark and one antiquark, which corresponds perfectly to mesons. But how can it explain baryons? My information and...
  5. PeroK

    Insights A Beginner Physics Guide to Baryon Particles

    [url="https://www.physicsforums.com/insights/a-beginners-guide-to-baryons/"]Continue reading...
  6. lalo_u

    A Delta Baryon Quartet: Constructing from SU(2) Symmetry

    In ##SU(2)## symmetry, we can define a triplet as ##2\otimes 2^*=3\oplus 1## with a tensor representation like this: $$q_iq_j^*=\left(q_iq^j-\frac{1}{2}\delta_j^iq_kq^k\right)+\frac{1}{2}\delta_j^iq_kq^k.$$ The upper index denotes an anti-doublet and the traceless part in parentheses represents...
  7. Demystifier

    I Why do dark matter and baryon matter have different distributions?

    Dark matter is distributed in halos around visible galaxies, while baryon matter is distributed in spiral-shaped visible galaxies. Where does this difference come from?
  8. F

    A Exploring the Existence of Baryons with Positive Strangeness

    Hi all, I read on "Intoduction to Elementary Particle Physics" (A. Bettini) that baryons with positive strangeness cannot exist. I don't know what to conclude from this sentence: sigma-baryons have negative strangeness, since there's a sigma as valence quark. But these baryons have, of course...
  9. 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
  10. 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?
  11. Jimmy Ridley

    Conservation principles and particle-particle reactions

    Please can someone help explain these to me? I have completed a-d but I'm not how e works. I thought gamma was an exchange particle so should it then decay further?
  12. G

    I Conservation of Lepton and Baryon numbers

    I am considerably confused about conservation laws like lepton number (L), baryon number (B) and comparable. Unlike the conservation laws for energy, momentum, angular momentum and electric charge, the conservations of L and B are not rigorously covered in textbooks. So my questions -...
  13. C

    I Are resonances formed in the scattering of a baryon and a meson?

    Consider the following reaction of strong interaction (in a scattering process) $$n+\pi^+\to \Lambda_0+K^+\tag{1}$$ Then the particle ##\Lambda_0## formed decays with weak interaction $$\Lambda_0\to \pi^+ +p\tag{2}$$ For each decay process I measure the four momenta of ##K^+##, ##\pi^+##...
  14. C

    Solving for X's Baryon & Lepton Number

    Homework Statement Homework EquationsThe Attempt at a Solution I worked out that the baryon number of X is 0 and the lepton number is +1 which means x is a lepton. However, when I work out the charge of X, do I add W+ to the left hand side or right hand side of the equation? [/B]
  15. Buzz Bloom

    I Why is a statistical explanation for Baryon Asymmetry wrong?

    I apologize if this is not the correct forum for this thread. I have tried to find a discussion regarding this question on the Internet without any success. The Wikipedia discussion https://en.wikipedia.org/wiki/Baryon_asymmetry makes no mention of any statistical explanation, so I understand...
  16. Kajagoogooooooo

    I Majorana neutrinos, sphaleron reactions, baryon asymmetry

    I`ve spent some time reading about the baryon asymmetry and the Sakharov`s conditions, and there some things I didn't exactly get: 1. Interactions out of thermal equilibrium: isn't it trivial? our universe is expanding so, of course, it out of equilibrium. 2. CP violation: I`ve read that Cronin...
  17. Kajagoogooooooo

    I Baryon asymmetry of the universe

    I don't understand why CP violation is insufficient to explain the observed baryon asymmetry? in every article I find it says: "we know its insufficient..." without an explanation. I will be glad for an explanation and for articles that deal with this issue. And how do you solve it using the...
  18. 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...
  19. C

    Can charged baryons flow induce magnetic field?

    We all think that electric current is the electrons flow without mass transfer in conductor, i.e. charged lepton flow. But charged baryons flow can also deemed as "electric" current, e.g. ionic current. My question is that charged baryons flow can induce magnetic field? Same amperes, then same B...
  20. stevendaryl

    I Baryon number nonconservation in the early universe

    It is said that the imbalance of matter versus antimatter in the present universe implies CP violations at very high energy. It seems to me that it most directly implies baryon number nonconservation: If we assume (and I'm not exactly sure why this is a necessary assumption) that immediately...
  21. S

    I Feynman Diagram for Double Charm Baryon

    This Feynman diagram accompanied the announcement on the public LHCb site. How would you describe the origins of the up and down quark anti-quark pairs that that contribute to the decay of the ##\Xi_{cc}^{++}##?
  22. V

    Parity violation in lambda baryon decay

    Homework Statement In the weak decay of the lambda baryon to a proton and pion, parity is not conserved, allowing for s and p waves in the orbital wave function of the pion-proton system. Using non-relativistic wavefunctions, find the angular distribution of the protons relative to the...
  23. T

    I Semileptonic Lambda baryon decay suppression

    Hi there, I'm currently studying the decay modes of the Lambda baryon (uds). According to literature, the decay mode with leptons (e.g. Lambda -> p + e- + anti ve) is suppressed against the decay modes with pions (e.g. Lambda -> p + pi-) by a factor of about 10^-4. I was looking for the reason...
  24. C

    I Is baryon antisymmetry always true?

    The baryon wavefunction is comprised of the direct product of contributions forming different Hilbert spaces such that $$|\Psi \rangle = |\text{spin} \rangle \otimes |\text{flavour}\rangle \otimes | \text{colour}\rangle \otimes |\text{space}\rangle. $$ The necessity for a colour degree of...
  25. Eric Putney

    I Can a (uuu) baryon exist? If so, why wouldn't protons decay

    Is this some sort of issue with color or another quantity that needs to be conserved?
  26. E

    What is the maximum energy of the Λ particle after the Σ0 baryon decay?

    Homework Statement A Σ0 baryon, traveling with an energy of 2 GeV, decays electromagnetically into a Λ and a photon. What condition results in the Λ carrying the maximum possible energy after the decay? Sketch how the decay appears in this case, and calculate this energy. Explain your...
  27. Doctor Strange

    I Is BAO a standing or moving wave?

    The sound horizon is the distance that a wave of plasma can move from the end of Inflation to Recombination (roughly 300,000 years). In several papers and talks, this is described as a moving wave (see https://www.youtube.com/watch?v=JSqIBRbQmb0 at the 23 minute mark). The velocity of the wave...
  28. Chronos

    B Evidence for CP violation in the baryon sector

    This paper; https: //arxiv.org/abs/1609.05216, Measurement of matter-antimatter differences in beauty baryon decays, provides the first evidence for CP violation in the baryon sector. This potentially explains a longstanding mystery - why the universe became dominated by matter while anti matter...
  29. M

    I Gravitational acceleration and the baryon distribution

    <<Mentor note: Moved from this thread>> I read this article http://thedaily.case.edu/rotating-galaxies-distribution-normal-matter-precisely-determines-gravitational-acceleration/ It claims that the rotation of galaxies can be explained without a need for dark matter. I not an educated...
  30. X

    I Find Lambda Baryon Decays Cross Section Ratio

    I've been asked to find the ratio between the cross sections of the two folowing decais: Using the CKM matrix and the feynman diagrams for both decays, I reach the conclusion that the Ratio is exactly 1. However, consulting this document...
  31. Xico Sim

    I Obtaining the decuplet of baryon states from one state

    Hi, guys. If you are given one state of the baryon decuplet (the upper-right state ##\Deltaˆ{++}=uuu##, for instance), you can use the ladder operators to get the other states of the decuplet. When I apply ##T_-## to uuu and normalizing, I get ##\frac{1}{\sqrt{3}}(duu+udu+uud)##. However, in...
  32. Garlic

    A Why doesn't pdg baryon list show quark compositions?

    Why doesn't pdg baryons list show the quark compositions and electrical charges? For example, there is only one roper resonance entry, but there are two roper resonances with different quark compositions (although they have the same mass), why not list all the variations?
  33. C

    What Are the Symmetry and Orthogonality Properties of Baryon Decuplet States?

    Homework Statement Consider composite states of three quarks, that transform as 3 ⊗ 3 ⊗ 3. The action of the corresponding raising and lowering operators on a typical state in this tensor product representation is $$I_+^{3 ⊗ 3 ⊗ 3} = I_+^3 \otimes \text{Id} \otimes \text{Id} + \text{perms}$$...
  34. C

    How do I determine if a certain nuclear decay is allowed?

    Hi, I am struggling with a question where they want me to determine whether or not three different decay are allowed. From what I have understood all decays must follow a set of conservation law. These laws are: 1 Conservation of Baryon number 2 Conservation of Lepton number 3 Conservation of...
  35. G

    Why Does Increased Baryon Loading Shift Power Spectrum to Higher Multipoles?

    About the power spectrum: if increased the number of baryons the frequency of the oscillation reduced.I want to ask why this fact moves the power spectrum to higher multipoles and no to smaller?smaller frequency doesn't mean longer wavelength and thus smaller multipoles?
  36. Andrea M.

    How do baryons transform under chiral transformations?

    I'm trying to understand how to construct effective lagrangians for the hadrons. I understand the procedure for the mesons but I get stuck on baryons. In particular I don't understand how the baryons should transform under a chiral transformation. I mean for the mesons it was easy because they...
  37. Garlic

    Omega Baryon Decay: Why Create Unnecessary Particles?

    Hello, Why is there a decay mode of omega baryon that creates unnecessary particles? sss -> uds + u(bar)s and why not just sss -> dss ?
  38. N

    In M-theory, is a baryon a D4 brane with three strings?

    I've read in a few string theory documents that have 10d spacetime that a baryon is a D4 brane with three strings (each being a quark), but what about in M theory?
  39. L

    Law of baryon conservation questions

    I am unclear about this law of the conservation of baryons; does it mean that the number of leptons can change OR the number of baryons but not both? Also, does it mean that no experimental evidence shows that baryons can decay into mesons. Can someone state clearly the law of conservation of...
  40. wolram

    Baryon oscillation peak a cosmological standard ruler

    This came up in the arxivs and had me thinking can this be true? arXiv:1506.05478 [pdf, ps, other] Is the baryon acoustic oscillation peak a cosmological standard ruler? Boudewijn F. Roukema, Thomas Buchert, Hirokazu Fujii, Jan J. Ostrowski Comments: 4 pages, 2 figures Subjects: Cosmology and...
  41. K

    Baryon number conservation in early universe when T<m

    When temperature of the universe falls below nucleon mass ##T<<1## GeV, the number densities of nucleons (proton and neutron) which are in kinetic equilibrium can be obtained as ##n_i=g_i (\frac{m_i T}{2\pi})^{3/2} e^{\frac{\mu_i-m_i}{T}}##. Since baryon number should be conserved, then I...
  42. X

    So why does baryon octet have the extra spin?

    baryon decuplet and octet have same quark content, but has spin 1/2 and 3/2. So what gives octet the extra spin?
  43. wolram

    How can BAO and SN constraints be compared for measuring dark energy?

    How do BAO help us measure dark energy? thank you for all the help PF members give in the cosmology forum.
  44. G

    Baryon Asymmetry explained by MWI

    I did some cursory searching, and I couldn't find this idea being discussed, so I thought it would be a good idea to bring it up here. Is there any reason why a valid explanation for baryon asymmetry isn't that we happen to live in a world branch where there was a significant asymmetry in the...
  45. A

    Why Mesons Can't Be Made of 2 Quarks Alone

    As far as I know a Baryon is made of three Quarks (eg uud, udd etc) and a Meson of two Quarks, a Quark/Antiquark pair. As I am not a student / scholar in Physics but very deeply interested in this field, I couldn't find any explanation, why a Meson is omly made up by a Quark/Antiquark pair. What...
  46. U

    Quick question on Baryon spin states

    Things I don't understand: What do they mean by "two spin-1/2 doublets and a spin-3/2 quadruplet"? Why do they use the two flavours "+2/3e and -1/3e" ?
  47. D

    Baryon acoustic oscillations and sound horizon

    I'm having some trouble understand this correctly, so I was hoping someone could enlighten me a bit :) Okay, so in the early Universe most of the hydrogen and helium was formed, and then kept in equilibrium, and ionized via photons. So we have a plasma of baryonic matter, including dark matter...
  48. Z

    Could Excited Baryon decay into omega meson and baryon?

    Excited baryon could decay into photon and ground state baryon,but could it decay into omega meson and ground state baryon?Could you introduce me some articles about it,experimental or theoretical?
  49. zubair

    Having trouble combing through PDG's site

    Hey Folks, I wanted to put together a single spreadsheet of subatomic particles (e-, ν, b, t, π Ξ, Σ, Δ, etc.) and their properties that have been measured (mass, mean lifetime, valence quark content, charge, spin, parity, etc.). I have been looking through the PDG website for some way to...
  50. S

    Possible Explanation for Baryon Asymmetry

    The reason why there is far more matter than anti-matter in our universe is because we are going forward in time. But if we reverse the direction of time anti-matter will become more prominent and I believe that at singularity there is a balance between both of them. The interaction between them...
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