Neutrino Masses in Theories with Dynamical Electroweak Symmetry Breaking

TL;DR

This paper tackles the problem of generating small neutrino masses within dynamical electroweak symmetry breaking frameworks, focusing on extended technicolor (ETC) theories. It proposes a two-part mechanism: naturally suppressed Dirac masses together with a dynamical seesaw driven by $|\Delta L|=2$ Majorana condensates among SM-singlet ETC-nonsinglet fermions, realized explicitly in a detailed ETC model. The model yields a light neutrino scale $m_{\nu,\max}$ of order $0.05$ eV and large $\nu_\mu-\nu_\tau$ mixing without requiring superheavy Majorana masses, since the relevant $M_R$ entries can be far below the highest ETC scale. The work demonstrates a viable path to neutrino masses within dynamical EWSB and motivates further refinement to match the full oscillation data while assessing phenomenological consequences.

Abstract

We address the problem of accounting for light neutrino masses in theories with dynamical electroweak symmetry breaking. We discuss this in the context of a class of (extended) technicolor (ETC) models and analyze the full set of Dirac and Majorana masses that arise in such theories. As a possible solution, we propose a combination of suppressed Dirac masses and a seesaw involving dynamically generated $|ΔL|=2$ condensates of standard-model singlet, ETC-nonsinglet fermions. We show how this can be realized in an explicit ETC model. An important feature of this proposal is that, because of the suppression of Dirac neutrino mass terms, a seesaw yielding realistic neutrino masses does not require superheavy Majorana masses; indeed, these Majorana masses are typically much smaller than the largest ETC scale.

Figures (4)

• Figure 1: Graphs generating $\bar{n}_{i,L} b_{ij} \alpha_{1j,R}$ for $i=1,2,3$ and $j=2,3$, assuming that the indicated mixings of ETC gauge bosons occur.
• Figure 2: One-loop graph contributing to the gauge boson mixing $V_3^4 \leftrightarrow V_5^2$. The graph with indices 4 and 5 interchanged on the internal $\zeta$ lines also contributes.
• Figure 3: Graphs for $\alpha_{12,R}^T C r_{23} \alpha_{13,R}$ in case $G_b$.
• Figure 4: One-loop graph for the ETC gauge boson mixing $V_1^4 \leftrightarrow V^1_5$ in case $G_b$. The graph with indices 4 and 5 interchanged on the internal $\zeta$ lines also contributes.