A few days ago I read an article in the November 2012 Scientific American, by Don Lincoln of Fermilab, "The Inner Life of Quarks," that describes arguments that quarks and leptons are not themselves fundamental, but rather are made up of more fundamental objects named "preons." The fact that leptons and quarks come in three known "families", with a hierarchy of increasing mass across them, and where the members of heavier families decay rapidly into the equivalent members of the lightest family, suggests the more-massive families' members are just excited forms of the lightest. Since it is difficult to see how a truly fundamental object can have excited states, more fundamental constituents seem likely.
In the preon model described in the article, which is said to be only one of several that have been put forward, there are two different fundamental preons, termed the "plus (+)" and the "zero (0)", along with their antiparticles. The plus and its antiparticle have electrical charge, while the zero and its antiparticle do not.
The gluons that are the carriers of the strong force are also composite objects made of the same set of preons.
Lincoln writes and illustrates that the preon model does a good job of representing the known hierarchy of the various families of quarks and leptons and their associated bosonic force particles. But, according to the article, there is a fundamental problem with the preon model: because the masses of the leptons and quarks are already established, there is no room in it to accommodate the masses of force carrying particles needed to bind like-charged preons into the various charged quarks and leptons. For example, gluons in the Standard Model account for most of the proton mass, while the up and down quarks are quite light comparatively. Particles to bind preons with similar charges as quarks would need to be at least as massive as the gluons, and so would lead to larger quark masses than observed. This is where the anti-centrifugal force of the Thomas precession can help. It provides a mechanism for overcoming electrostatic repulsion that does not require mediation by massive force-carrying particles. It is simply a kinematical necessity of
charged particles and electrostatic forces existing in flat Minkowski spacetime.
The anti-centrifugal force of the Thomas precession and its apparent manifestation in Maxwell-Lorentz electrodynamics, as the magnetic force on a relativistic charge moving in the magnetic field created by a Coulomb-accelerating relativstic charge, and how Coulomb repulsion is overcome at extremely small interparticle separations, is described in my arxiv paper http://arxiv.org/abs/1108.4343. I often call this force the strong magnetic force.
Remarkably, application at the scale of the preon model solves a problem I have been having with trying to apply the strong magnetic force directly as binding ultra-relativstic quarks into nucleons without reference to gluons. This nucleon model is similar to the MIT Bag Model and so is not completely without precedent. However, apart from being directly contradictory to the now very well established Standard Model, I have not obtained that it is strong enough to bind as large an object as a nucleon. I get that the strong magnetic force overcomes Coulomb repulsion at a separation that is about one one-hundredth of the measured size of the proton. This would seem indeed to make it a better candidate to bind preons into quarks, than to bind quarks into nucleons. Even more remarkably, here it seems the strong magnetic force need not contradict any established physics, and its lack of need for force carrying particles is an essential characteristic for making the preon model work.
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