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 νAν 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 (δm2, | ∆m2 |, sin2 θ12, sin2 θ13, sin2 θ23), and the status of the three remaining unknown parameters: the mass hierarchy [sign (± ∆m2)], the θ23 octant [sign (sin2 θ23 - 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 δm2 and sin2 θ12, while the latest accelerator and atmospheric data induce a slight increase of | ∆m2 |. 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 θ23 octant or the mass hierarchy (normal or inverted). Assuming an alternative (so-called LEM) analysis of NO νA 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 νe mass mβ (in beta decay), and the effective Majorana mass mββ (in neutrinoless double beta decay).
Nuclear Physics B
- Pub Date:
- July 2016
- High Energy Physics - Phenomenology
- 15 pages, 9 figures, 2 tables. Invited contribution prepared for the Nuclear Physics B Special Issue on "Neutrino Oscillations" celebrating the Nobel Prize in Physics 2015