Classically Conformal B-L extended Standard Model

Abstract

Under a hypothesis of classically conformal theories, we investigate the minimal B-L extended Standard Model, which naturally provides the seesaw mechanism for explaining tiny neutrino masses. In this setup, the radiative gauge symmetry breaking is successfully realized in a very simple way: The B-L gauge symmetry is broken through the conformal anomaly induced by quantum corrections in the Coleman-Weinberg potential. Associated with this B-L symmetry breaking, the Higgs mass parameter is dynamically generated, by which the electroweak symmetry breaking is triggered. We find that a wide range of parameter space can satisfy both the theoretical and experimental requirements.

Figures (4)

• Figure 1: The RG improved effective potential. Here, we have taken $\alpha_{B-L}(0)=0.01$, accordingly $\alpha_\lambda(0)=-1.91 \times 10^{-4}$ and $C = 1.27$ are fixed so that the effective potential has its minimum at $\phi/M=1$.
• Figure 2: The SM singlet Higgs boson mass as a function of the Yukawa coupling. Here we have taken $\alpha_{B-L}(0)=0.01$ and accordingly, fixed $\alpha_\lambda(0)$ to satisfy the stationary condition in Eq. (\ref{['condition']}). For $\alpha_N(0) \simeq 9.8 \alpha_{B-L}(0)$, the potential minimum at $\phi=M$ changes into the maximum.
• Figure 3: One-loop diagram inducing the mixing term $(\Phi^\dagger \Phi)(H^\dagger H )$ through the right-handed neutrinos.
• Figure 4: Two-loop diagrams inducing the mixing term $(\Phi^\dagger \Phi)(H^\dagger H )$ through the top-quarks and the $B-L$ gauge bosons. The wavy lines represent the propagators of the $B-L$ gauge bosons.