Rishon Model

The Harari–Shupe preon model (also known as rishon model, RM) is the earliest effort to develop a preon model to explain the phenomena appearing in the Standard Model (SM) of particle physics. It was first developed by Haim Harari and Michael A. Shupe (independently of each other), and later expanded by Harari and his then-student Nathan Seiberg.

The model has two kinds of fundamental particles called rishons (which means "primary" in Hebrew). They are T ("Third" since it has an electric charge of +⅓ e, or Tohu which means "unformed" in Hebrew Genesis) and V ("Vanishes", since it is electrically neutral, or Vohu which means "void" in Hebrew Genesis). All leptons and all flavours of quarks are three-rishon ordered triplets. These groups of three rishons have spin-½. They are as follows:

Each rishon has a corresponding antiparticle. Hence:

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 (such as proton decay) in the model would be
 u  +  u  →  d  +  e⁺
/|\   /|\   /|\   /|\
TTV + TTV → TVV + TTT

In the expanded Harari–Seiberg version [1] 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.

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