Global constraints on absolute neutrino masses and their ordering

Abstract

Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta (0νββ) decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(10 −1 ) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, 0νββ decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of ∼ 2σ, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the χ 2 method, by expanding the parameter space either around separate minima in NO and IO, or around the absolute minimum in any ordering. Implications for upcoming oscillation and non-oscillation neutrino experiments, including β-decay searches, are also discussed.

Consequences of minimal seesaw with complex μτ antisymmetry of neutrinos

“…For the computation of Y B we need to evaluate the parameters of m D (i.e., a 1,2 , b 1,2 ) and Table 2. Input values fed into the analysis [45].…”

“…A sizable amount of work has earlier been done using [43,44] the real µτ antisymmetry idea -including its application to the neutrino masses and mixing as well as its possible group theoretic origin from a more fundamental flavor symmetry such as A 5 . However, the major phenomenological problem with exact real µτ antisymmetry is that it leads to a maximal solar neutrino mixing angle θ 12 = π/4 as well as two degenerate light neutrinos -in conflict with experiment [45]. Perturbative modifications, in attempts to address these problems, unfortunately lead to a proliferation of extra unknown parameters.…”

Broken S 3L × S 3R flavor symmetry and leptonic CP violation

“…(8), and the unitary matrix V l depends only on two mass ratios. By making use of the running charged-lepton masses at the energy scale of M Z = 91.…”

“…Although the normal ordering of neutrino masses (i.e., m 1 < m 2 < m 3 ) is slightly favored and there is a preliminary hint of a nearly-maximal CP -violating phase δ ≈ 261 • or equivalently δ ≈ −99 • , the possibility of an inverted mass ordering (i.e., m 3 < m 1 < m 2 ) and CP conservation in the leptonic sector has not yet been excluded [6]. See also the independent global-fit results from two other groups [7][8][9]. An unambiguous determination of neutrino mass ordering and a robust discovery of leptonic CP violation in neutrino oscillations are two primary goals of future medium-baseline reactor (e.g., JUNO [10] and RENO-50 [11]) and long-baseline accelerator neutrino experiments (e.g., T2K [12], NOνA [13] and LBNF-DUNE [14]).…”

The μ-τ reflection symmetry of Dirac neutrinos and its breaking effect via quantum corrections

“…Given I e ≃ I µ ≃ 1 and I τ ≃ 1 − ∆ τ and the µ-τ reflection symmetry at Λ µτ , it is easy to check that the product of m where η ≡ sin δ = ±1 in the µ-τ reflection symmetry limit, and [70,71]. On the other hand, the smallness of s 13 [72] implies that the magnitude of ∆θ 13 must be smaller than that of ∆θ 23 .…”