Active-sterile neutrino mixing in the ISS(p,q) inverse seesaw models

Abstract

A class of models with inverse seesaw mechanism is considered for arbitrary numbers p and q of new neutral fermions for each generation of leptons. The models containing a candidate particle for the role of warm dark matter are sorted using the inversion technique of an arbitrary block matrix in terms of Schur complement. Unlike the seesaw type I and II models with keV sterile dark matter neutrinos, in the inverse seesaw models mixing does not depend on the mass of dark matter particle, but depends only on the mass of heavy sterile pseudo-Dirac neutrinos.

Figures (3)

• Figure 1: Numerical simulation of the mass spectrum for the ${\rm ISS}\left(\text{2},\text{3}\right)$ model with a viable warm Dark Matter candidate at the keV scale for non-diagonal complex matrix $\mu$, $m_{\nu,~{\rm atm}} = \sqrt{|\Delta m_{21}^2|}$, $m_{\nu~{\rm solar}} = \sqrt{|\Delta m_{32}^2|}$, where $\Delta m_{ij}^2$ are differences of squared masses of the active neutrinos from oscillation data pdg2024, $\Lambda(m_D)$, $\Lambda(M_R)$ and $\Lambda(\mu)$ denote the scales of the matrix blocks $m_D$, $M_R$ and $\mu$. Yukawa natural hierarchy mode is used with $Y=e^{X_1} + i e^{X_2}$ and $X_1, X_2$ are random real numbers with uniform distribution on the range $[\ln{(10^{-3})};0]$.
• Figure 2: Lower bound on the $\Lambda(M_R)$ scale following from NuSTAR and XMM 2021 data is shown by solid line. Solid line corresponds to a recalculation of data taken from Gorbunov_xray_new. No significant dependence on Yukawa parameters generation is observed due to the summation of the mixing components from \ref{['eq:uudm-mixing']}.
• Figure 3: Contour plot for the dark matter sterile neutrino mixing parameter $U_{\rm DM}^2$ on the parametric plane of ISS energy scales $\Lambda(m_D)$ and $\Lambda(M_R)$. The mixing matrix is calculated numerically by the SVD decomposition method Horn_Johnson_book for the complete symmetric mass matrix $\mathbf{M}_{(2,3)}$. The red region, where the mass scale of active neutrinos is too large, is excluded. The grey domain is excluded by $X$-ray astrophysical observations, see nuSTARXMM and also Gorbunov_xray_new. The values of mixing parameter $U_{\rm DM}^2$ for each contour are shown in rounded frames.