Harari Rishon Model
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Haim Harari is a physicist who made one of the earliest efforts to develop a preon model to explain the phenomena appearing in the Standard Model (SM) of particle physics. Persons unfamiliar with preons should read about them before trying to review this particular model. His 1979 model is set forth in brief below (with lower case denoting antiparticles). The model was later expanded and improved by Harari and his then student Nathan Seiberg, currently one of the leading string theorists.
An equivalent model to the original Harari proposal was proposed independently and simultaneously by Michael A. Shupe, both Harari's original paper and Shupe's being published consecutively in the same issue of the same journal, although Harari's paper was submitted earlier and the published version of Shupe's paper has been revised. The fact that Harari's name and terminology are remembered, while Shupe's are largely forgotten, can be viewed as something of an unfair historical accident.
[edit] The model
The model has two kinds of fundamental particles called rishons (which means "primary" in Hebrew). They are T ("Third", for charge 1/3 e or "Tohu" which means "unformed" in Hebrew Genesis) and V ("Vanishes", for charge zero, or "va-Vohu" which means "void" in Hebrew Genesis). All leptons and all flavours of quarks are three-rishon combinations. These groups of three rishons have spin 1/2. They are as follows:
- TTT = positron;
- VVV = electron neutrino;
- TTV, TVT and VTT = three colours of "up" (u) quarks;
- TVV, VTV and VVT = three colours of "down" (d) antiquarks.
Each rishon has antiparticles. Hence:
- ttt = electron;
- vvv = anti-electron neutrino;
- ttv, tvt, vtt = three colours of anti-u quarks;
- vvt, vtv, tvv = three colours of d quarks.
The W+ boson = TTTVVV; The W− boson = tttvvv.
Baryon number (B) and lepton number (L) are not conserved, but the quantity B-L is conserved. A baryon number violating process (proton decay) in the model would be U+U → d+positron which in rishon terms is: TTV+TTV → TVV+TTT.
Matter and anti-matter are equally abundant in nature in the theory.
Higher generation leptons and quarks are presumed to be excited states of first generation leptons and quarks. Mass is not explained.
In the expanded Harari-Seiberg version the Rishons possess color and Hypercolor, explaining why the only composites are the observed quarks and leptons.Under certain assumptions, it is possible to show that the model allows exactly for three generations of quarks and Leptons, a fact never explained.
Currently there is no evidence whatsoever for a substructure of quarks and leptons, but there is no profound reason why such substructure will not be revealed at shorter distances.
[edit] The Rishon Model in Popular Culture
Science fiction author Vonda McIntyre, in her novelizations of the scripts of the movies Star Trek II: The Wrath of Khan and Star Trek III: The Search for Spock suggested that the Genesis effect was a result of a newly-discovered rishon-like substructure to matter.
Science fiction author James P. Hogan in his novel Voyage from Yesteryear explicitly postulated a rishon-like model in the development of antimatter weapons.
[edit] References
- Harari, H.; A Schematic Model of Quarks and Leptons, Physics Letters B, Vol. 86, No. 1, pp. 83–86 (1979) [1]
- Shupe, M. A.; A Composite Model of Leptons and Quarks, Physics Letters B, Vol. 86, No. 1, pp. 87–92 (1979) [2]
