ETC With a GIM Mechanism

TL;DR

This work demonstrates that Extended Technicolor consistent with a GIM mechanism and a minimal technicolor sector can be constructed, preserving custodial SU(2) and allowing massless neutrinos within a controlled framework. By employing separate ETC groups for left-handed, up-type, and down-type fermions and a single technicolor sector, the authors achieve fermion mass generation while suppressing FCNC through approximate global symmetries and near-degenerate ETC gauge bosons, yielding a mass formula $m \approx M \left(\frac{v}{f}\right)^3$. They present two explicit models—one with low flavor dynamics and another with a high flavor scale—illustrating different ways to realize a nontrivial KM matrix and addressing phenomenology such as light pseudogoldstone bosons and potential leptoquark states. The paper also discusses hypercharge embedding via a simple U(1) construction, neutrino mass possibilities, and custodial symmetry protection of the $\rho$ parameter, outlining a rich program for future theoretical and experimental exploration. Overall, the results suggest a promising direction for technicolor theories to remain compatible with precision data while offering distinctive collider signatures.

Abstract

We construct an extended technicolor model of quarks and leptons which preserves a GIM mechanism. Furthermore, there is only a minimal technicolor sector, in accordance with recent precision measurements of electroweak parameters. We also show how to incorporate custodial SU(2) and massless neutrinos into such a model.