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History of particle discovery

  1. Jul 23, 2008 #1
    Hi everbody,

    I am currently learning about the quark model in more detail, how the multipletts are constructed and so on. However, I wonder what particles were really found in that time? I found a list somewhere in the net stating:

    1937: [tex]\mu[/tex]
    1946: [tex]K^0,\bar K^0[/tex]
    1947: [tex]\pi^-, \pi^+, K^+, K^-[/tex]
    1949: [tex]\pi^0[/tex]
    1951: [tex]\Lambda[/tex]
    1952: [tex]\Xi^-[/tex]
    1953: [tex]\Sigma^-[/tex], [tex]\Sigma^+[/tex]
    1955: [tex]\bar p[/tex]n
    1956: [tex]\Sigma^0[/tex], [tex]\nu_e[/tex]
    1959: [tex]\Xi^0[/tex]
    1961: [tex]\eta[/tex]
    1962: [tex]\nu_\mu[/tex]
    1964: [tex]\Omega^-[/tex]

    But then, in this list there are e.g. no Delta-Baryons but it is always said that Gell-Mann knew about them in order to fill the dekuplett. Also, what about the rho-mesons, the omega and such? Is there any reference out there where the dates of discovery are written?

    Thanks for your help!
    Last edited by a moderator: Jul 23, 2008
  2. jcsd
  3. Jul 24, 2008 #2
    It's a good question now that I think about more seriously. I was going to tell you that, obviously, the original references are in the Particle Data Group book. However, they say " Most of the results published before 1975 were last included in our 1982 edition". Then, when do you consider the publication as an official discovery becomes problematic. Everybody expected the [itex]\Delta[/itex] from quark models. The current reference (Nucl. Phys. A300 (1978) 321) quotes Nucl. Phys. B58 (1973) 378 as providing "some evidence for a slight violation of charge independence". So I guess the only way to make up one's mind is to look at them one by one...
  4. Jul 25, 2008 #3

    Vanadium 50

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    This can't be true. The Delta would have been discovered in the very early 1950's, between 1951 (completion of the Chicago Cyclotron) and 1954 (Fermi's death). Quark theory didn't exist until 1964.
  5. Jul 25, 2008 #4
    I'm puzzled. I'm just saying, once people had constructed quark models of hadrons, they expected a delta resonance. Am I crazy !?
  6. Jul 25, 2008 #5
    I think I understand :smile:
    The Chicago group published a hint of the first ever resonance now called [itex]\Delta^0[/tex] in 1954. What I was saying is that now PDG refers to a more robust measurement from like 1979, which can be called direct observation. But yes, this hint of [itex]\Delta^0[/tex] was part of the motivation for the quark model itself. Once the quark model accepted, nobody had any doubt that this hint of resonance was true.

    So in the end, it's best to look up the original references in any case.
  7. Jul 25, 2008 #6

    Vanadium 50

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    I'm saying the Delta(1232) predates this by a decade.
  8. Jul 25, 2008 #7

    Vanadium 50

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    I don't think this is right. My copy of Frauenfelder and Henley from 1974 has several pages on the Delta. It wouldn't have this if it weren't directly discovered until 5 years later. They also reproduce the PDG tables from 1973, and the Delta is listed as a 4-star resonance - "good, clear and unmistakable".

    By 1979, there was charm, bottom, jets, QCD, and UA1/UA2 were just over the horizon.
  9. Jul 25, 2008 #8
    I already quoted :
    In the printed version I have right here (2006, to be updated in a couple of weeks?), they say results from before 1977 are obsolete. I can't get the 1982 edition right now. Why did they dismiss previous results if they were already 4 stars, explain me... I also already said
    and I have the plot from 1954 right before my eyes.

    In any case, they had the quark model from the mid 60' so there was certainly not any much more discussion about the existence of the [itex]\Delta[/tex]. Only after did they understand that the quark model is not the end of the story.

    I think this is getting pretty dull at this point. The original question was "where to find those dates altogether". I can only point to the PDG with the earliest possible reference, and start from there for digging. Please provide a better, up-to-date reference with historical references.
  10. Jul 26, 2008 #9


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    Keith A. Brueckner
    Department of Physics, Indiana University, Bloomington, Indiana

    Received 17 December 1951

    The scattering (including charge exchange) of π- mesons in hydrogen rises from 18 millibarns at 60 Mev to a broad plateau of about 60 millibarns at 200 Mev, and is smaller than the π+ scattering at 60 Mev in the ratio of 0.63±0.09. The general features of the π- scattering, except for the high energy plateau, are given qualitatively by pseudoscalar theory with pseudovector coupling in the weak coupling limit; the ratio of π- to π+ scattering predicted by this theory in the weak coupling limit is, however, 1.67, which is much higher than the experimental result. A phenomenological theory of the scattering is developed by using the methods of Wigner and Eisenbud and imposing the restrictions of charge symmetry. By using the qualitative assignment of the resonance levels parameters as given by weak and strong coupling theory, satisfactory agreement with experiment is obtained. It is concluded that the apparently anomalous features of the scattering can be interpreted to be an indication of a resonant meson-nucleon interaction corresponding to a nucleon isobar with spin 3 / 2, isotopic spin 3 / 2, and with an excitation of 277 Mev.

    ©1952 The American Physical Society

    URL: http://link.aps.org/abstract/PR/v86/p106
    DOI: 10.1103/PhysRev.86.106
  11. Jul 26, 2008 #10


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    I need to find my copy of Frauenfelder and Henley. :grumpy: I think there were hints of a baryon/nucleon resonance in the early 50's. I guess the question is when the resonance was recognized as [itex]\Delta[/itex], and when it was realized that fractional charges were involved.

    Here's my contribution:

    M. Gell-Mann, The Eightfold Way: A Theory of Strong Interaction Symmetry, March 15, 1961

    Murray Gell-Mann, Symmetries of Baryons and Mesons, Phys. Rev. 125, 1067 - 1084 (1962)

    Gell-Mann announced the quark in 1963, but was thinking about it earlier.

    Origin of the word 'quark'
    Murray Gell-Mann, physicist, assigned the name "quark" to the fundamental constituents of the nucleon back in 1963. Further details are found in his book The Quark and the Jaguar published in paperback in 1995.
    The Quark and the Jaguar
    From Page 180:

    Phys. Rev. Lett. 17, 789 - 793 (1966)
    Production of the Nucleon Isobars 1236, 1410, 1518, and 1688 MeV in Proton-Proton Collisions at 2.85, 4.55, 6.06, and 7.88 GeV/c
    I. M. Blair and A. E. Taylor
    Atomic Energy Research Establishment, Harwell, England

    W. S. Chapman, P. I. P. Kalmus, J. Litt *, M. C. Miller, D. B. Scott, and H. J. Sherman
    Queen Mary College, London, England

    A. Astbury and T. G. Walker
    Rutherford High Energy Laboratory, Chilton, Berkshire, England

    Received 11 August 1966; revised 14 September 1966
    See also -
    M. Gell-Mann, Phys. Lett. 8, 214 (1964); G. Zweig, CERN report No. 8182 TH 401 (1964).


    Higher Symmetry Schemes for Strong Interactions
    L. Van Hove
    Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 288, No. 1413 (Oct. 26, 1965), pp. 156-160

    See - A study of the fractional charge content of the cosmic radiation

    Update: Delta: the first pion nucleon resonance - its discovery and applications; Nagle, D.; October 26, 1999; LALP--84-27; ACC0011
    Last edited by a moderator: May 3, 2017
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