B Non-Conservation, Cold Dark Matter and Subpreon Model

Now we have, as simple elements of Nature, leptons, quarks, electromagnetic interactions, strong interactions based on the three colors, weak interactions due to the weak boson exchange and gravity. A main task of the present-day particle physics is to find internal relations among such simple elements and to disclose a more profound essence of Nature. In order to connect known interactions, it is almost certain that one mu~t introduce new interactions. If leptons and quarks are taken fundamental as in the GUT approach, it necessarily restricts properties of newly introduced interactions severely because the interactions acting among leptons and quarks are required to satisfy special properties. In the GUT approach, all interaction must be like QCD and a possible choice is only what gauge group is taken. On the other hand, if we take a composite model of leptons and quarks (namely pre on models), new interactions can be taken more flexibly because properties of preons are not so restricted. This flexibility would be fruitful to clarify an essence of Nature.· This point is one of virtues of preon models. We believe that one of the key phenomena to consider physics in the preon world is the very existence of lepton and quark with their unique properties. It will be especially important to find a way by which we can explain naturally the facts that the electric charges of them are very different from each other and that quarks with abnormal charges have a color quantum number. The author has recently proposed a preon modeP) along this line of thought by introducing preons with charge e/2 as well as the preonic charge which is identified with the magnetic charge. This model has some interesting features. Among them, the following may be of fundamental importance. (1) It is an inevitable consequence that particles with an abnormal electric charge couple with other exact gauge fields. This nicely explains the existence of another exact gauge symmetry (namely QCD) besides QED and gives the reason why quarks have a color quantum number. (2) The quark charge e/3 is a natural consequence of the charge of preon (=e/2) and the number of the color (=3).