Reconciling TM$_2$ Mixing with LMA and Dark-LMA Data based on Minimal Corrections from Charged-Lepton Sector

TL;DR

This paper investigates minimal charged-lepton sector corrections to the TM2 neutrino mixing framework, reconciling it with current LMA and dark-LMA data, and predicts sizeable CP violation and testable neutrinoless double beta decay parameters.

Contribution

It introduces a Wolfenstein parameterization-based correction model that aligns TM2 mixing with recent neutrino oscillation data, including both LMA and dark-LMA solutions.

Findings

Allowed parameter ranges for 7; and 7; are identified for LMA and dark-LMA.

The upper bound on 7; is constrained by atmospheric mixing angle 7; in the LMA case.

The model predicts large CP violation, with 7; reaching up to 0.13.

Abstract

Motivated by the increasing precision of neutrino oscillation data, we study the corrections to the TM$_2$ neutrino mixing framework, emanating from $(1,2)$ sector of the charged lepton, for both the standard LMA and dark-LMA solutions. We employ the Wolfenstein parameterization of the charged-lepton mixing matrix, characterized by two additional parameters $(\lambda,\delta)$, which effectively reconciles the TM$_2$ neutrino-mixing predictions with current oscillation data. For the LMA solution, the allowed ranges are $0.1 \lesssim \lambda \lesssim 0.33$ and $\delta \in (20^\circ\!-\!90^\circ)\oplus(270^\circ\!-\!340^\circ)$, while the dark-LMA case requires $\lambda>0.24$ and $125^\circ<\delta<235^\circ$. Interestingly, for LMA case, the upper bound $\lambda \le 0.33$ is found to be dictated by the atmospheric mixing angle $\theta_{23}$. The model predicts sizeable CP violation, with $|J_{CP}|$ reaching values as large as $0.13$. We, also, analyze the effective Majorana mass parameter $m_{ee}$ relevant for neutrinoless double beta decay. The inverted hierarchy region lies within the sensitivity of future experiments for both solutions, whereas only part of the normal hierarchy region can be tested.