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A New Level of Structure

SEP 01, 1985
In the standard model of matter, there are five stages of compositeness—molecules, atoms, nuclei, nucleons, and quarks and leptons—but we are beginning to see regularities at the fifth layer that may point to a deeper, sixth level of structure.
O. W. Greenberg

The history of the physics of the small is in great measure the story of the discovery of new levels of structure, each associated with the development of a new set of experimental tools, and ultimately with a new discipline. We have repeatedly categorized some set of particles as the elementary constituents of matter, only to discover later that these should properly be considered as composed of yet‐more‐fundamental particles. Discounting the prescientific view of matter as composed of Air, Fire, Earth, and Water, five levels of structure have been discovered so far, as shown in table 1. Most readers of this article are probably familiar with the evidence for each level of structure; a good review of this evidence can be found in reference 1.

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References

  1. 1. S. Weinberg, The Discovery of Subatomic Particles, Freeman, New York (1983).

  2. 2. L. Lyons, Prog. Part. Nucl. Phys. 10, 227 (1983).https://doi.org/PPNPDB

  3. 3. M. E. Peskin, in Proc. 10th Intl. Symp. Lepton‐Photon Interactions at High Energy, W. Pfeil, ed., Univ. Bonn, Bonn, FRG (1981), p. 880.

  4. 4. R. D. Peccei, ECFA‐CERN Workshop on Feasibility of Hadron Colliders in the LEP Tunnel, CERN, Geneva (1984), p. 329.

  5. 5. O. W. Greenberg, R. N. Mohapatra, S. Nussinov, Phys. Lett. 148B, 465 (1984).https://doi.org/PYLBAJ

  6. 6. J. Wess, J. Bagger, Supersymmetry and Supergravity, Princeton U.P., Princeton, N.J. (1983).

  7. 7. B. Schrempp, F. Schrempp, DESY preprint 84/055, May 1984.

More about the authors

O. W. Greenberg, University of Maryland, College Park.

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This Content Appeared In
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Volume 38, Number 9

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