Instanton-mediated baryon number violation in non-universal gauge extended models

Abstract

Instanton solutions of non-abelian Yang-Mills theories generate an effective action that may induce lepton and baryon number violations, namely $\Delta B=\Delta L=n_f$, being $n_f$ the number of families coupled to the gauge group. In this article we study instanton mediated processes in a $SU(2{)}_{\ell }\otimes SU(2{)}_h\otimes U(1)$ extension of the Standard Model that breaks universality by singularizing the third family. In the construction of the instanton Green functions we account systematically for the inter-family mixing. This allows us to use the experimental bounds on proton decay in order to constrain the gauge coupling of $SU(2{)}_h$. Tau lepton non-leptonic and radiative decays with $\Delta B=\Delta L=1$ are also analysed.

Comments: 33 pages, 3 figures. Further explanations about the instanton solutions for the G(221) model added in a new appendix, conclusions unchanged. Version published in JHEP