Neutrino masses and mixings: Status of known and unknown 3ν parameters

By Francesco Capozzi, E. Lisi, A. Marrone, D. Montanino, A. Palazzo. 2016

268 citations recorded by the source corpus.

Abstract Within the standard 3ν mass–mixing framework, we present an up-to-date global analysis of neutrino oscillation data (as of January 2016), including the latest available results from experiments with atmospheric neutrinos (Super-Kamiokande and IceCube DeepCore), at accelerators (first T2K ν ‾ and NO ν A ν runs in both appearance and disappearance modes), and at short-baseline reactors (Daya Bay and RENO far/near spectral ratios), as well as a reanalysis of older KamLAND data in the light of the “bump” feature recently observed in reactor spectra. We discuss improved constraints on the five known oscillation parameters ( δ m 2 , | Δ m 2 | , sin 2 ⁡ θ 12 , sin 2 ⁡ θ 13 , sin 2 ⁡ θ 23 ), and the status of the three remaining unknown parameters: the mass hierarchy [ sign ( ± Δ m 2 ) ], the θ 23 octant [ sign ( sin 2 ⁡ θ 23 − 1 / 2 ) ], and the possible CP-violating phase δ. With respect to previous global fits, we find that the reanalysis of KamLAND data induces a slight decrease of both δ m 2 and sin 2 ⁡ θ 12 , while the latest accelerator and atmospheric data induce a slight increase of | Δ m 2 | . Concerning the unknown parameters, we confirm the previous intriguing preference for negative values of sin ⁡ δ (with best-fit values around sin ⁡ δ ≃ − 0.9 ), but we find no statistically significant indication about the θ 23 octant or the mass hierarchy (normal or inverted). Assuming an alternative (so-called LEM) analysis of NO ν A data, some δ ranges can be excluded at > 3 σ , and the normal mass hierarchy appears to be slightly favored at ∼ 90 % C.L. We also describe in detail the covariances of selected pairs of oscillation parameters. Finally, we briefly discuss the implications of the above results on the three non-oscillation observables sensitive to the (unknown) absolute ν mass scale: the sum of ν masses Σ (in cosmology), the effective ν e mass m β (in beta decay), and the effective Majorana mass m β β (in neutrinoless double beta decay).

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3bfc04832fcd03771149ce7b2b51139c533e8424

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Citations in the corpus

Invited review: Physics potential of the ICAL detector at the India-based Neutrino Observatory (INO) (2015, background): “The current best-fit values and allowed ranges of these parameters may be found in [55, 56, 54].”
Sterile neutrinos in cosmology (2017, background): “The splittings of the mass eigenstates are becoming more precisely measured in neutrino oscillation experiments [43], while determining the value of the absolute mass in the laboratory requires the accurate measurement of the endpoint of the spectrum of beta-decay neutrinos [44].”
Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise Neff evaluation (2018, background): “Furthermore, given the observed pattern of masses and mixings [40–42] the neutrino oscillations become active in the early Universe for temperatures T = 3− 5 MeV [43, 44] (see Appendix A.”
Updated results on neutrino mass and mass hierarchy from cosmology with Planck 2018 likelihoods (2019, unknown): “See [10–15] for results from other global analyses.”
Global constraints on absolute neutrino masses and their ordering (2017, methodology): “An analysis of neutrino oscillation data has been previously presented in [9], to which we refer the reader for a discussion of the adopted methodology and earlier literature.”
Constraints on flavor-diagonal non-standard neutrino interactions from Borexino Phase-II (2019, unknown): “[72], which includes neither Borexino Phase I nor Phase II data, is small and does not affect the present analysis.”
Relic neutrino decoupling with flavour oscillations revisited (2016, unknown): “where s(2)ij ≡ sin(2) θij , that correspond to the best-fit values from the global analysis of neutrino oscillation experiments in [22] (using the values found in more recent analyses [23, 24] does not modify our results).”