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A bstract Our herein described combined analysis of the latest neutrino oscillation data presented at the Neutrino2020 conference shows that previous hints for the neutrino mass ordering have significantly decreased, and normal ordering (NO) is favored only at the 1 . 6 σ level. Combined with the χ 2 map provided by Super-Kamiokande for their atmospheric neutrino data analysis the hint for NO is at 2 . 7 σ . The CP conserving value δ CP = 180° is within 0 . 6 σ of the global best fit point. Only if we restrict to inverted mass ordering, CP violation is favored at the ∼ 3 σ level. We discuss the origin of these results — which are driven by the new data from the T2K and NOvA long-baseline experiments —, and the relevance of the LBL-reactor oscillation frequency complementarity. The previous 2 . 2 σ tension in ∆ m 2 21 preferred by KamLAND and solar experiments is also reduced to the 1 . 1 σ level after the inclusion of the latest Super-Kamiokande solar neutrino results. Finally we present updated allowed ranges for the oscillation parameters and for the leptonic Jarlskog determinant from the global analysis.

A bstract We present an updated global analysis of neutrino oscillation data as of September 2024. The parameters θ 12 , θ 13 , ∆ m 21 2 , and ∣ ∆ m 3 ℓ 2 ∣ ( ℓ = 1 , 2) are well-determined with relative precision at 3 σ of about 13%, 8%, 15%, and 6%, respectively. The third mixing angle θ 23 still suffers from the octant ambiguity, with no clear indication of whether it is larger or smaller than 45 ° . The determination of the leptonic CP phase δ CP depends on the neutrino mass ordering: for normal ordering the global fit is consistent with CP conservation within 1 σ , whereas for inverted ordering CP-violating values of δ CP around 270 ° are favored against CP conservation at more than 3 . 6 σ . While the present data has in principle 2 . 5–3 σ sensitivity to the neutrino mass ordering, there are different tendencies in the global data that reduce the discrimination power: T2K and NOvA appearance data individually favor normal ordering, but they are more consistent with each other for inverted ordering. Conversely, the joint determination of ∣ ∆ m 3 ℓ 2 ∣ from global disappearance data prefers normal ordering. Altogether, the global fit including long-baseline, reactor and IceCube atmospheric data results into an almost equally good fit for both orderings. Only when the χ 2 table for atmospheric neutrino data from Super-Kamiokande is added to our χ 2 , the global fit prefers normal ordering with ∆ χ 2 = 6 . 1. We provide also updated ranges and correlations for the effective parameters sensitive to the absolute neutrino mass from β -decay, neutrinoless double-beta decay, and cosmology.

In this contribution, we summarise the determination of neutrino masses and mixing arising from global analysis of data from atmospheric, solar, reactor, and accelerator neutrino experiments performed in the framework of three-neutrino mixing and obtained in the context of the NuFIT collaboration. Apart from presenting the latest status as of autumn 2021, we discuss the evolution of global-fit results over the last 10 years, and mention various pending issues (and their resolution) that occurred during that period in the global analyses.

We adopt the quantum field theoretical method to calculate the amplitude and event rate for a neutrino oscillation experiment, considering neutrino production, propagation and detection as a single process. This method allows to take into account decoherence effects in the transition amplitude induced by the quantum mechanical uncertainties of all particles involved in the process. We extend the method to include coherence loss due to interactions with the environment, similar to collisional line broadening. In addition to generic decoherence induced at the amplitude level, the formalism allows to include, in a straightforward way, additional damping effects related to phase-space integrals over momenta of unobserved particles as well as other classical averaging effects. We apply this method to neutrino oscillation searches at reactor and Gallium experiments and confirm that quantum decoherence is many orders of magnitudes smaller than classical averaging effects and therefore unobservable. The method used here can be applied with minimal modifications also to other types of oscillation experiments, e.g., accelerator based beam experiments.

We present the results of a global analysis of the neutrino oscillation data available as of fall 2018 in the framework of three massive mixed neutrinos with the goal at determining the ranges of allowed values for the six relevant parameters. We describe the complementarity and quantify the tensions among the results of the different data samples contributing to the determination of each parameter. We also show how those vary when combining our global likelihood with the χ2 map provided by Super-Kamiokande for their atmospheric neutrino data analysis in the same framework. The best fit of the analysis is for the normal mass ordering with inverted ordering being disfavoured with a Δχ2 = 4.7 (9.3) without (with) SK-atm. We find a preference for the second octant of θ23, disfavouring the first octant with Δχ2 = 4.4 (6.0) without (with) SK-atm. The best fit for the complex phase is δCP = 215° with CP conservation being allowed at Δχ2 = 1.5 (1.8). As a byproduct we quantify the correlated ranges for the laboratory observables sensitive to the absolute neutrino mass scale in beta decay, mνe\\[ {m}_{\\nu_e} \\] , and neutrino-less double beta decay, mee, and the total mass of the neutrinos, Σ, which is most relevant in Cosmology.

A bstract In the presence of non-standard neutrino interactions (NSI), a degeneracy exists in neutrino oscillation data, which involves the flipping of the octant of the mixing angle θ 12 and the type of the neutrino mass ordering. In this article, we revisit the status of this degeneracy in the light of recent data on coherent elastic neutrino-nucleus scattering (CE ν NS) from the COHERENT experiment. For general relative couplings to up and down quarks, the degeneracy is disfavoured at the 2 σ level by the latest data but remains at a higher confidence level. We investigate the requirements of future CE ν NS measurements to resolve the degeneracy with high significance. We find that a measurement involving both, electron and muon neutrino flavours and a target with a neutron-to-proton ratio close to 1 is required. For example, an experiment with a silicon target at the European Spallation Source can resolve the degeneracy at more than 4 σ for arbitrary relative couplings to up and down quarks.

A bstract Cosmological constraints on the sum of the neutrino masses can be relaxed if the number density of active neutrinos is reduced compared to the standard scenario, while at the same time keeping the effective number of neutrino species N eff ≈ 3 by introducing a new component of dark radiation. We discuss a UV complete model to realise this idea, which simultaneously provides neutrino masses via the seesaw mechanism. It is based on a U(1) symmetry in the dark sector, which can be either gauged or global. In addition to heavy seesaw neutrinos, we need to introduce 𝒪(10) generations of massless sterile neutrinos providing the dark radiation. Then we can accommodate active neutrino masses with ∑ m ν ~ 1 eV, in the sensitivity range of the KATRIN experiment. We discuss the phenomenology of the model and identify the allowed parameter space. We argue that the gauged version of the model is preferred, and in this case the typical energy scale of the model is in the 10 MeV to few GeV range.

A bstract We discuss the possibility to explain the anomalies in short-baseline neutrino oscillation experiments in terms of sterile neutrinos. We work in a 3 + 1 framework and pay special attention to recent new data from reactor experiments, IceCube and MINOS+. We find that results from the DANSS and NEOS reactor experiments support the sterile neutrino explanation of the reactor anomaly, based on an analysis that relies solely on the relative comparison of measured reactor spectra. Global data from the ν e disappearance channel favour sterile neutrino oscillations at the 3 σ level with Δ m 41 2  ≈ 1.3 eV 2 and | U e 4 | ≈ 0 . 1, even without any assumptions on predicted reactor fluxes. In contrast, the anomalies in the ν e appearance channel (dominated by LSND) are in strong tension with improved bounds on ν μ disappearance, mostly driven by MINOS+ and IceCube. Under the sterile neutrino oscillation hypothesis, the p -value for those data sets being consistent is less than 2 . 6 × 10 −6 . Therefore, an explanation of the LSND anomaly in terms of sterile neutrino oscillations in the 3 + 1 scenario is excluded at the 4 . 7 σ level. This result is robust with respect to variations in the analysis and used data, in particular it depends neither on the theoretically predicted reactor neutrino fluxes, nor on constraints from any single experiment. Irrespective of the anomalies, we provide updated constraints on the allowed mixing strengths | U α 4 | ( α = e, μ, τ ) of active neutrinos with a fourth neutrino mass state in the eV range.

A bstract We perform a combined fit to global neutrino oscillation data available as of fall 2016 in the scenario of three-neutrino oscillations and present updated allowed ranges of the six oscillation parameters. We discuss the differences arising between the consistent combination of the data samples from accelerator and reactor experiments compared to partial combinations. We quantify the confidence in the determination of the less precisely known parameters θ 23 , δ CP , and the neutrino mass ordering by performing a Monte Carlo study of the long baseline accelerator and reactor data. We find that the sensitivity to the mass ordering and the θ 23 octant is below 1 σ . Maximal θ 23 mixing is allowed at slightly more than 90% CL. The best fit for the CP violating phase is around 270°, CP conservation is allowed at slightly above 1 σ , and values of δ CP ≃ 90° are disfavored at around 99% CL for normal ordering and higher CL for inverted ordering.

A bstract We present a global analysis of solar, atmospheric, reactor and accelerator neutrino data in the framework of three-neutrino oscillations based on data available in summer 2014. We provide the allowed ranges of the six oscillation parameters and show that their determination is stable with respect to uncertainties related to reactor neutrino and solar neutrino flux predictions. We find that the maximal possible value of the Jarlskog invariant in the lepton sector is 0.033 ±0.010 (±0.027) at the 1 σ (3 σ ) level and we use leptonic unitarity triangles to illustrate the ability of global oscillation data to obtain information on CP violation. We discuss “tendencies and tensions” of the global fit related to the octant of θ 23 as well as the CP violating phase δ CP . The favored values of δ CP are around 3π/2 while values around π /2 are disfavored at about Δχ 2 ≃6. We comment on the non-trivial task to assign a confidence level to this Δ χ 2 value by performing a Monte Carlo study of T2K data.