2017/11/30 by Soumita Pramanick · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #CP violation #Lepton #MAJORANA #Mass matrix #Matrix (chemical analysis) #Mixing (physics) #Neutrino #Neutrino Physics Research #Neutrino oscillation #Octant (instrument) #Particle physics #Particle physics theoretical and experimental studies #Physics #Pontecorvo–Maki–Nakagawa–Sakata matrix #Quantum mechanics #Solar neutrino #Type (biology) #hep-ex #hep-ph
paper · pdf · doi:10.1103/physrevd.98.075016
published as Phys. Rev. D 98, 075016 (2018) · 31 pages, 2 figures, 5 tables, v3: version to appear in Physical Review D
openalex created_date 2017/11/17 · arxiv created 2018/10/03 · openalex publication_date 2018/10/17 · arxiv updated 2018/10/24 · openalex updated_date 2026/08/05
A model for neutrino masses and mixing is presented using the seesaw mechanism. The model combines type-I and type-II seesaw contributions of which the latter dominates. The scalars and the leptons in the model are assigned A4 charges suitable to obtain the mass matrices required for the scheme. The type-II seesaw accommodates atmospheric mass splitting and maximal mixing in the atmospheric sector (\ensuremathθ23=\ensuremathπ/4). It is characterized by vanishing solar mass splitting and \ensuremathθ13 whereas the third neutrino mixing angle can acquire any value, \ensuremathθ120. Particular alternatives of \ensuremathθ120 viz. \ensuremathθ120=35.3\ifmmode^∘\else\textdegree\fi (tribimaximal), 45.0\ifmmode^∘\else\textdegree\fi (bimaximal), 31.7\ifmmode^∘\else\textdegree\fi (golden ratio) are accounted for. Another choice of \ensuremathθ120=0\ifmmode^∘\else\textdegree\fi (no solar mixing) is also considered. Incorporating the corrections provided by the subdominant type-I seesaw involves degenerate perturbation theory due to vanishing solar splitting in the type-II seesaw enabling the solar mixing angle to receive substantial corrections. Apart from amending the solar sector, the type-I seesaw also tunes all the neutrino oscillation parameters into the allowed ranges, thus interrelating them all. Thus, the model is testable in the light of future experimental data. As an example, \ensuremathθ23 emerges in the first (second) octant for normal (inverted) ordering. CP-violation is controlled by phases present in the right-handed Majorana neutrino mass matrix, M_\ensuremathνR. Only normal ordering is allowed if these phases are absent. If M_\ensuremathνR is complex the Dirac CP-violating phase \ensuremathδ, can be large, i.e., \ensuremath∼\ifmmode±\else\textpm\fi\ensuremathπ/2, and inverted ordering is also allowed. T2K and NOVA preliminary data favoring normal ordering and \ensuremathδ\ensuremath∼\ensuremath-\ensuremathπ/2 predicts lightest neutrino mass to be 0.05 eV or more within the model framework.