Minimal Radiative Neutrino Mass Mechanism for Inverse Seesaw Models (1209.4051v3)

Abstract: We study a minimal one-loop radiative mechanism for generating small Majorana neutrino masses in inverse seesaw extensions of the Standard Model with two singlet fermions per family. The new feature of this radiative mechanism is that the one-loop induced left-handed neutrino mass matrix is directly proportional to the Majorana mass matrix of the right-handed neutrinos. This is a very economical scenario without necessitating the existence of non-standard scalar or gauge fields.

• The paper introduces a novel one-loop radiative mechanism to generate small Majorana neutrino masses using the inverse seesaw model.
• It employs additional singlet fermions and SM quantum effects from Z and Higgs bosons, easing hierarchy constraints in neutrino mass generation.
• Numerical analysis shows that the lepton-number violating parameter μR can be significantly larger than μS, aligning theoretical predictions with oscillation data.

Minimal Radiative Neutrino Mass Mechanism for Inverse Seesaw Models

The paper, "Minimal Radiative Neutrino Mass Mechanism for Inverse Seesaw Models" by P. S. Bhupal Dev and Apostolos Pilaftsis, explores a sophisticated approach toward elucidating the mass puzzle associated with neutrinos. Engaging with the inverse seesaw framework, the authors propose a novel mechanism for generating small Majorana neutrino masses in the Standard Model (SM) extensions. Their approach involves a one-loop radiative process which integrates two additional singlet fermions per family, offering an economical scheme that bypasses the need for new scalar or gauge fields.

Core Proposition

In traditional seesaw mechanisms, the introduction of heavy right-handed neutrinos provides an elegant solution to the problem of small neutrino masses. The inverse seesaw model further extends this by utilizing a pair of sterile singlet states, enhancing the mass generation process. Unlike the usual seesaw models that generate light neutrino masses at tree level, the authors present a mechanism wherein these masses arise at the one-loop level. Crucially, this radiative effect is directly proportional to the Majorana mass matrix of the right-handed neutrinos.

Technical Exposition

The paper systematically examines how SM quantum effects, particularly involving the electroweak Z and Higgs bosons, induce the neutrino mass radiatively. It posits a condition wherein the dimension-3 lepton-number violating matrix $\mu_R$ is non-zero, enabling the one-loop mechanism. The implications of this setup are captured within the UV-finite light neutrino mass formula:

$$M^{\text{1-loop}}_{\nu_L} \simeq \frac{f(x_N)}{m_W^2} M_D\mu_RM_D^{\sf T}$$

where $f(x_N)$ is the one-loop function indicating a dependence on the neutrino mass scale $x_N$. The authors emphasize that this configuration allows for a milder hierarchy between the lepton-number breaking and electroweak scales, addressing one of the significant challenges in neutrino physics.

Results and Implications

The detailed numerical analysis within the paper highlights how the lepton-number violating mass $\mu_R$ could be orders of magnitude larger than $\mu_S$, the typical lepton-number violating scale in standard inverse seesaw models. This attribute effectively mitigates the need for extreme hierarchical suppression and suggests the feasibility of maintaining neutrino masses coherent with experimental oscillation data.

Moreover, the analysis extends to the general inverse seesaw model with both $\mu_R$ and $\mu_S$ being non-zero. Here, the paper constructs mappings between the effective neutrino mass matrix $\bar{\mu}_{\rm eff}$ and oscillation data, offering insights into flavor structure and parameter space that underline potential experimental validations.

Future Outlook

This paper enriches theoretical understanding by not only refining inverse seesaw models but also setting a precedent for future explorations in particle physics. The formulation of the minimal radiative inverse seesaw model paves the way for potential extensions into supersymmetric frameworks, where it may further alleviate hierarchical constraints and contribute to dark matter modeling. It provides intriguing prospects for improved integration with SM and beyond, inviting speculative ventures into addressing longstanding questions about neutrinos and New Physics.

The paper forms a compelling argument for exploring radiative mechanisms in seesaw models and challenges existing paradigms by introducing practical and theoretically robust innovations.