What are the difficulties of the rishon model?

[Prishon]

The risbon model model was inveted by Harari in 1981. It is a theory that lies beyond the standard model and explains the existence of quarks and leptons on the basis of jusr 2 elementary particles, the T- and V-rishon (heuristically that is, like the quark model did once for the plethora of hadrons and mesons).

But what are its drawbacks? Apart from the trivial answer that it is not proven. Though the muon g2 is a strong hint that the muon consists of three anti T-rishons (and for example, the up quark consists of two T-rishons and one V-rishon). The mass of the neutrino is another hint of compositeness (together with the seesaw mechanism, another possibility to account for neutrino mass).

 

[ohwilleke]

The risbon model model was inveted by Harari in 1981. It is a theory that lies beyond the standard model and explains the existence of quarks and leptons on the basis of jusr 2 elementary particles, the T- and V-rishon (heuristically that is, like the quark model did once for the plethora of hadrons and mesons).

But what are its drawbacks? Apart from the trivial answer that it is not proven. Though the muon g2 is a strong hint that the muon consists of three anti T-rishons (and for example, the up quark consists of two T-rishons and one V-rishon). The mass of the neutrino is another hint of compositeness (together with the seesaw mechanism, another possibility to account for neutrino mass).

The main problems are that experimental data is so far inconsistent with a composite nature for quarks and leptons up to a very high energy scale (24 TeV or more by the most strict exclusion), and with very low electric (as opposed to magnetic) dipole moments (consistent with zero) of quarks and leptons. The rishon model also doesn't account for the fact that we observe three generations of Standard model fermions. The experimental bounds in quark and lepton compositeness are summarized at the Particle Data Group. These limits are explained in a related review article.

See also the discussions of experimental barriers including the mass paradox in this discussion of preons more generally. In a nutshell, the Heisenberg uncertainty principle would indicate uncertainty in the fundamental particle masses much greater than observed if indeed they were composite particles that are at least as small as experimental observations require.

Also, muon g-2 proves no such thing. Indeed, there are two completing theoretical calculations of muon g-2's expected value, one of which incorporates more experimental measurements, and the other of which is more fully from first principles calculations by the BMW group, and the later is perfectly consistent with the experimental measurements of muon g-2 which would suggest that there is no muon g-2 anomaly to explain.

Further, to the best of my knowledge, there have been no efforts to describe a rishon model in terms of muon g-2 or composite leptons.

The mass of the neutrino is strong evidence that the pre-massive neutrino Standard Model was missing something. It is not evidence of compositeness in particular. None of the leading theories seeking to explain the source of neutrino mass resort to a composite neutrino model.

 

[Prishon]

That is not an answer to my question. I know all data can be explained in the standard framework. But also in the rishon framework. And it even offers an explanation for the three families of quarks and leptons. I asked for difficulties in the model itself. I once asked Harari on the internet but can't remember. He is now out of reach. I think energy and chirality play a role. In 2017 the theory was reanimated. Do you know something of this model?

 

[Prishon]

There is nothing that compositeness forbids. There is no experimental evidence yet. But that was the same for the quark model when it was introduced in 1961. Only at the end of that decade the experimental proof was accbepted. Feynman spoke of his partons. He never liked quarks. Professor Cosmas Zachos heard him being mad at quarks. But there were difficulties with quarks. They couldn't be observed directly. What are the difficulties with this already 40 years (!) old model? Theoretical difficulties obviously. What about potential and kinetic energies at that small distances? Can a very strong force hold three masskess particles together?( the rishons are quark-like because they carry hypercolor, a strong variant of the color charge).

 

[PeterDonis]

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