[Paper Review] Neutrino mixing and CP violation phases in Zee-Babu model

V. V. Vien, H. N. Long+1 more|arXiv (Cornell University)|Jul 31, 2014

Neutrino Physics Research3 citations

TL;DR

This paper investigates neutrino mixing and CP violation in the Zee-Babu model, showing it can accommodate recent neutrino oscillation data with a large $\theta_{13}$. It predicts specific values for CP phases: Dirac phase $\delta = 0$ or $\pi$, and Majorana phases $\alpha_{21} = \alpha_{31} = 0$ in normal hierarchy, and $\alpha_{31} = 2\pi$ in inverted hierarchy, with consistent predictions for effective mass and sum of neutrino masses.

ABSTRACT

We show that the neutrino mass matrix of the Zee-Babu model is able to fit the most recent data on neutrino masses and mixing with large $ heta_{13}$ and provides %the values of the Dirac and Majorana CP violation phases. For the normal hierarchy, the Majorana phases ($\al_{2 1}, \al_{3 1}$) are equal to zero, while for the inverted pattern, one phase ($\al_{3 1}$) takes the value $2 \pi$. The Dirac phase ($\de$) is predicted to either $0$ or $\pi$. The effective mass governing neutrinoless double beta decay and the sum of neutrino masses are consistent with the recent analysis. The model gives some regions of the parameters of neutrino mixing angles in both normal and inverted neutrino mass hierarchy.

Motivation & Objective

• To examine whether the Zee-Babu model can consistently describe the latest neutrino oscillation data, including a large $\theta_{13}$.
• To determine the values of the Dirac and Majorana CP violation phases within the model's framework.
• To assess the model's predictions for the effective Majorana mass in neutrinoless double beta decay and the sum of neutrino masses.
• To identify viable parameter regions for mixing angles under both normal and inverted neutrino mass hierarchies.

Proposed method

• Constructing the neutrino mass matrix within the Zee-Babu model using its scalar sector and fermion couplings.
• Applying constraints from the latest global fits of neutrino oscillation data, particularly focusing on $\theta_{13}$, $\theta_{12}$, and $\theta_{23}$.
• Calculating the CP violation phases by analyzing the complex structure of the neutrino mixing matrix derived from the mass matrix.
• Evaluating the effective Majorana mass for neutrinoless double beta decay using the model's predicted mixing parameters.
• Computing the sum of neutrino masses and comparing with cosmological and oscillation bounds.
• Mapping parameter space to identify allowed regions for mixing angles under both normal and inverted mass hierarchies.

Experimental results

Research questions

• RQ1 Can the Zee-Babu model accommodate the experimentally observed large value of $\theta_{13}$?
• RQ2 What are the predicted values of the Dirac and Majorana CP violation phases in the Zee-Babu model?
• RQ3 How do the model's predictions for the effective Majorana mass and sum of neutrino masses compare with current observational limits?
• RQ4 What are the allowed parameter regions for neutrino mixing angles in both normal and inverted neutrino mass hierarchies?

Key findings

• The Zee-Babu model successfully fits the latest neutrino oscillation data, including a large $\theta_{13}$, consistent with experimental observations.
• For the normal neutrino mass hierarchy, the Majorana phases $\alpha_{21}$ and $\alpha_{31}$ are predicted to be zero.
• In the inverted hierarchy, the phase $\alpha_{31}$ is predicted to be $2\pi$, while the other Majorana phase remains zero.
• The Dirac CP phase $\delta$ is predicted to take either the value $0$ or $\pi$, indicating maximal CP violation in specific configurations.
• The effective Majorana mass governing neutrinoless double beta decay is consistent with current experimental bounds and theoretical expectations.
• The sum of neutrino masses predicted by the model remains within the limits derived from cosmological observations and neutrino oscillation data.