Abstract
There are several reasons for taking into account the possibility that quarks and leptons are composite particles1. We recall the recent discoveries of new quarks and leptons and their apparent organization in families. Furthermore, quarks and leptons must be intimately connected, as shown for instance by the fact that |Q(electron)| = Q(proton). The emerging picutre is one in which quarks and leptons are indeed composite particles made up of the same elementary entities. Many models have been proposed so far2, but none of them can be considered completely satisfying. Another reason to consider quarks and leptons as composite particles has been pointed out by ‘t Hooft 3,4 As it is well known, in a broken gauge theory, the Higgs fields give rise to many arbitrary parameters (masses, Yukawa couplings, vacuum expectation values). Furthermore, they give origin to instabilities in the theory against small variations of the parameters (see for instance L. Susskind5). A way out of these difficulties (unless supersymmetries regulate the theory) is the dynamical syimnetry breaking; i.e., Higgs fields must be regarded as fermion-antifermion bound states. An example of theories of this type is given by technicolor theories (TC)5, which howeverare uncapable of giving masses to the fermions unless further broken gauge interactions (extended technicolor ETC)6 are postulated.
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References
This talk is based on the papers: R. Casalbuoni and R. Gatto, University of Geneva preprint UGVA-DPT 1981/01–273; R. Casalbuoni and R. Gatto, to be published.
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Casalbuoni, R. (1981). Baryonic Number Nonconservation in Subcomponent Models for Quarks and Leptons. In: Perlmutter, A. (eds) Gauge Theories, Massive Neutrinos and Proton Decay. Studies in the Natural Sciences, vol 18. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-1107-2_16
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