2020 global reassessment of the neutrino oscillation picture

Abstract

We present an updated global fit of neutrino oscillation data in the simplest three-neutrino framework. In the present study we include up-to-date analyses from a number of experiments. Concerning the atmospheric and solar sectors, besides the data considered previously, we give updated analyses of IceCube DeepCore and Sudbury Neutrino Observatory data, respectively. We have also included the latest electron antineutrino data collected by the Daya Bay and RENO reactor experiments, and the long-baseline T2K and NOνA measurements, as reported in the Neutrino 2020 conference. All in all, these new analyses result in more accurate measurements of θ13, θ12, $$ \Delta {m}_{21}^2 $$ Δ m 21 2 and $$ \left|\Delta {m}_{31}^2\right| $$ Δ m 31 2 . The best fit value for the atmospheric angle θ23 lies in the second octant, but first octant solutions remain allowed at ∼ 2.4σ. Regarding CP violation measurements, the preferred value of δ we obtain is 1.08π (1.58π) for normal (inverted) neutrino mass ordering. The global analysis still prefers normal neutrino mass ordering with 2.5σ statistical significance. This preference is milder than the one found in previous global analyses. These new results should be regarded as robust due to the agreement found between our Bayesian and frequentist approaches. Taking into account only oscillation data, there is a weak/moderate preference for the normal neutrino mass ordering of 2.00σ. While adding neutrinoless double beta decay from the latest Gerda, CUORE and KamLAND-Zen results barely modifies this picture, cosmological measurements raise the preference to 2.68σ within a conservative approach. A more aggressive data set combination of cosmological observations leads to a similar preference for normal with respect to inverted mass ordering, namely 2.70σ. This very same cosmological data set provides 2σ upper limits on the total neutrino mass corresponding to Σmν< 0.12 (0.15) eV in the normal (inverted) neutrino mass ordering scenario. The bounds on the neutrino mixing parameters and masses presented in this up-to-date global fit analysis include all currently available neutrino physics inputs.

Electroweak symmetry breaking in the inverse seesaw mechanism

“…Here we note that neither the explicit nor the dynamical variant of the minimal (3,1,1) inverse seesaw mechanism is phenomenologically realistic. The reason is that (3,1,1) leads to only one massive neutrino (lying say, at the atmospheric scale), hence inconsistent with oscillation data [8]. This minimal scheme is simply the inverse seesaw embedding of the minimum "missing partner" (3,1) see saw mechanism of section III in ref.…”

“…Moreover, despite its many successes, the Standard Model cannot be the final theory of nature. One of its main shortcomings is its inability to account for neutrino mass generation, needed to describe neutrino oscillations [8]. The Higgs vacuum stability problem in neutrino mass models can become worse than in the Standard Model [9][10][11][12][13][14][15][16].…”

“…Modulo, of course, explaining the detailed pattern of mixing angles indicated by the oscillation data[8].Such a challenging task would require a family symmetry, whose detailed nature is not yet fully understood 7. This feature may also be implemented in some radiative schemes of scotogenic type, see e.g [55][56][57]…”

The inverse seesaw family: Dirac and Majorana

“…This would be the effective operator of the majoron model [27,28]. Operators including Φ (2) = H a H b , with H a and H b two different Higgs doublets, are induced in the context of the Two-Higgs-doublet model framework, for instance in supersymmetric models [29].…”

“…The discovery of neutrino oscillations provided us with one of the first and clearest experimental hints of shortcomings in the Standard Model (SM). This is because the SM predicts neutrinos to be exactly massless while neutrino oscillations irrefutably prove that at least two of the three known neutrinos should carry mutually non-degenerate masses [1,2]. However, neutrino masses were theoretically anticipated by model builders much before the experimental confirmation came.…”