Trimaximal mixing with one texture zero of the inverse neutrino mass matrix

In this paper, we study the phenomenological implications of enforcing one texture zero on the inverse matrix of the neutrino mass matrix [Formula: see text] that can lead to the trimaximal mixing. It is found that the condition of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] or [Formula: see text] can hold in the case of normal neutrino mass ordering, while the condition of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] or [Formula: see text] can hold in the case of inverted neutrino mass ordering, where [Formula: see text] (for [Formula: see text], [Formula: see text]) denotes the [Formula: see text] entry of the inverse matrix of [Formula: see text]. The ranges of the absolute neutrino mass scale and three CP phases for these cases to hold are studied in some detail. The implications of these cases for the effective neutrino mass [Formula: see text] which controls the rates of the neutrino-less double beta decay processes are also given.

Understanding of two-zero textures of neutrino mass matrices in minimal extended seesaw mechanism and their symmetry realization

We study the texture zeros of [Formula: see text] neutrino mass matrices [Formula: see text] in the minimal extended type-I seesaw (MES) mechanism, incorporating one extra gauge singlet field “[Formula: see text]”. The [Formula: see text] MES model deals with [Formula: see text] [Formula: see text], [Formula: see text] [Formula: see text] and [Formula: see text] mass matrix [Formula: see text] which couples the right-handed neutrinos and the singlet field “[Formula: see text]”. We carry out the mapping of all possible zero textures of [Formula: see text], [Formula: see text] and [Formula: see text] with the restriction to phenomenologically predictive cases having total eight zeros of [Formula: see text] and [Formula: see text] studied in the literature. If [Formula: see text], the sterile neutrino mass, is subject to any limit, further block diagonalization of [Formula: see text] shall not be allowed to reduce it to a [Formula: see text] matrix. In [Formula: see text] [Formula: see text] scenario, the study of texture zero is totally different and interesting. With this motivation, we consider the [Formula: see text] scheme where the digits of the pair represent the number of zeros of [Formula: see text] and [Formula: see text], respectively, along with the one/two-zero textures of [Formula: see text]. There are a large number of possibilities of zeros of fermion mass matrices, but the implementation of [Formula: see text] transformations reduces it to a very minimum number of basic structures. As the [Formula: see text] MES matrix is a matrix of rank 3, so we consider only those textures with two zeros which are of rank 3 whereby the number of feasible zero textures reduces to 12, out of 15. On realizing these 12 textures under MES mechanism with [Formula: see text] picture, we arrive at certain correlations for each texture. We examine the viability of each texture by scanning their respective correlations under recent neutrino oscillation data. Also, we discuss the interplay of Dirac and Majorana CP phases in determining the viability of a texture. The allowed two-zero textures are finally realized using a discrete Abelian flavor symmetry group [Formula: see text] with the extension of Standard Model to include some scalar fields.

Texture zero mass matrices and nature of neutrinos

For Majorana as well as Dirac neutrinos, attempt has been made to carry out a comparative study of the predictions of Fritzsch-like texture 6, 5 and 4 zero leptonic mass matrices. In particular, considering normal hierarchy of neutrino masses, we have examined how the parameter space available to the mixing angles with respect to the lightest neutrino mass changes for the two types of neutrinos.